Patent Application
20150097505
The present disclosure contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2013-212025 filed in the Japan Patent Office on Oct. 9, 2013, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The embodiments disclosed therein relate to current source inverter devices.
2. Description of the Related Art
There has been known a technology that switches a stator winding of an alternating-current (AC) motor from a low-speed winding to a high-speed winding by a winding switch if the rotation speed of the AC motor becomes high speed.
The technology reduces a counter voltage that is generated in the AC motor at high speed by switching the stator winding from the low-speed winding to the high-speed winding. Accordingly, the speed control range is expanded, and operation in a wide range from a low-speed region to a high-speed region becomes available (for example, see Japanese Patent No. 3948009).
However, the technology of the related art that switches the winding state of the AC motor uses, for example, a winding switch circuit. Further, a plurality of terminals and a plurality of wirings are provided for connection between the AC motor and the winding switch circuit. Therefore, there may be problems in viewpoints of reduction in size and reduction in weight of the AC motor.
According to an aspect of the disclosure, there is provided a current source inverter device including an inverter and a controller. The inverter supplies alternating-current power to a number n (n being an integer of 1 or greater) of alternating-current motors each having a number m (m being an integer of 2 or greater) of windings per phase. The controller controls the inverter and the alternating-current motor. The inverter includes a switching unit, in which a number n×m+1 of switching elements per phase of the alternating-current motor are connected in series, and a number n×m of nodes among the switching elements are respectively connected with a number n×m of different windings with the same phase among the windings of the number n of the alternating-current motors. The controller includes a selector that selects at least one winding as a supply target of the alternating-current power from the number n×m of the windings based on a rotation speed of the alternating-current motor.
Hereinafter, embodiments of current source inverter devices that are disclosed by the subject application are described in detail. It is to be noted that the disclosure is not limited to the embodiments described below.
The current source inverter device 2 converts DC power supplied from the DC source 4 into desirable AC power and outputs the AC power to the motor 3. The current source inverter device 2 is not limited to the configuration shown in
As shown in
The terminals TU1, TV1, and TW1 are connected with a first three-phase winding 5 included in the motor 3. Also, the terminals TP and TN are respectively connected with a positive electrode and a negative electrode of the DC source 4. Further, the terminals TU2, TV2, and TW2 are connected with a second three-phase winding 6 included in the motor 3.
The inverter 11 is connected with the DC source 4 through the terminals TP and TN. Further, the inverter 11 is connected with the motor 3 through the terminals TU1, TV1, and TW1, and the terminals TU2, TV2, and TW2.
The controller 20 is connected with the position sensor 10. The controller 20 controls the inverter 11 and the motor 3. The controller 20 selects one of or both the first three-phase winding 5 and the second three-phase winding 6 based on the rotation speed of the motor 3 for each phase of a U-phase, a V-phase, and a W-phase of the motor 3, and determines the selected three-phase winding as a supply target of AC power. Accordingly, the speed control range for the motor 3 can be expanded without switching the winding state of the motor 3. The details of the inverter 11 and the controller 20 are more specifically described later.
The motor 3 includes the first three-phase winding 5, the second three-phase winding 6, and a rotor 9. For example, the motor 3 is a motor having three-phase double windings formed of double windings in which stator windings are insulated from each other, for example, an induction motor or a permanent-magnet synchronous motor. The number of windings of each of the windings 5a, 5b, and 5c of the first three-phase winding 5, and the number of windings of each of the windings 6a, 6b, and 6c of the second three-phase winding 6 are the same. One end of the winding 5a is connected with the terminal TU1, one end of the winding 5b is connected with the terminal TV1, and one and of the winding 5c is connected with the terminal TW1. Also, one end of the winding 6a is connected with the terminal TU2, one end of the winding 6b is connected with the terminal TV2, and one end of the winding 6c is connected with the terminal TW2. The terminals are included in the current source inverter device 2.
The windings 5a, 5b, and 5c of the first three-phase winding 5 have polarities reverse to the windings 6a, 6b, and 6c of the second three-phase winding 6. To be specific, the two windings corresponding to each phase of the motor 3 are inserted into the same slot of the stator, are electromagnetically densely coupled to each other, and have winding directions with mutually reversed polarities. In
The rotor 9 is arranged to face a stator (the first three-phase winding 5 and the second three-phase winding 6). The other ends of the windings 5a, 5b, and 5c are mutually connected. Also, the other ends of the windings 6a, 6b, and 6c are mutually connected.
In the example in
The position sensor 10 is connected with an output shaft of the motor 3. The position sensor 10 detects a phase θ of the rotor 9 (hereinafter, referred to as rotor phase θ) of the motor 3, and outputs the detected phase θ to the controller 20. The position sensor 10 is, for example, an encoder or a resolver.
As shown in
The switching element units 13 to 15 each have three switching elements connected in series. To be specific, the switching element unit 13 includes three switching elements Q1u, Q2u, and Q3u connected in series. The switching element unit 14 includes three switching elements Q1v, Q2v, and Q3v connected in series. The switching element unit 15 includes three switching elements Q1w, Q2w, and Q3w connected in series.
The switching elements Q1u to Q3u, Q1v to Q3v, and Q1w to Q3w (hereinafter, occasionally collectively called switching element Qs) are each, for example, a reverse-direction stop insulated gate bipolar transistor (IGBT). In
The switching element units 13 to 15 each have two nodes among the switching elements Qs, and the two nodes are respectively connected with different two windings with the same phase of the motor 3. To be specific, regarding the switching element unit 13, a node N1u between the switching elements Q1u and Q2u is connected with the U1-phase of the motor 3, and a node N2u between the switching elements Q2u and Q3u is connected with the U2-phase of the motor 3.
Further, regarding the switching element unit 14, a node N1v between the switching elements Q1v and Q2v is connected with the V1-phase of the motor 3, and a node N2v between the switching elements Q2v and Q3v is connected with the V2-phase of the motor 3. Also, regarding the switching element unit 15, a node N1w between the switching elements Q1w and Q2w is connected with the W1-phase of the motor 3, and a node N2w between the switching elements Q2w and Q3w is connected with the W2-phase of the motor 3.
The filter 16a has capacitors whose one ends are respectively connected with the U1-phase terminal TU1, the V1-phase terminal TV1, and the W1-phase terminal TW1, and the other ends are commonly connected. Also, the filter 16b has capacitors whose one ends are respectively connected with the U2-phase terminal TU2, the V2-phase terminal TV2, and the W2-phase terminal TW2, and the other ends are commonly connected. The filters 16a and 16b each have a function of removing a high-frequency component of current of each phase output from each of the switching element units 13 to 15.
When the controller 20 controls the motor 3, the controller 20 generates a gate signal in a control mode corresponding to the rotation speed of the motor 3, and outputs the generated gate signal to the inverter 11. That is, the controller 20 converts the DC power supplied from the DC source 4 into the AC power by the inverter 11, then outputs the AC power to the motor 3, and controls the motor 3.
The controller 20 switches a control mode between two control modes in accordance with the rotation speed of the motor 3, and controls the inverter 11. The controller 20 selects a first control mode in a low-speed region in which the rotation speed of the motor 3 is relatively low, and selects a second control mode in a high-speed region in which the rotation speed of the motor 3 is relatively high. If the controller 20 selects the first control mode, the AC power is supplied in series to the first and second three-phase windings 5 and 6. If the controller 20 selects the second control mode, the AC power is supplied to only one of the first and second three-phase windings 5 and 6. The counter voltage generated in the motor 3 becomes lower in the second control mode than the counter voltage in the first control mode as long as the rotation speed of the motor 3 is the same.
With the control, the current source inverter device 2 can operate in a wide range from the low-speed region to the high-speed region. The control modes are successively described. Described below is an example in which the motor 3 is controlled by the controller 20 while a synchronous motor serves as a model, the synchronous motor being controllable by two-axis current having d-axis current (field current or magnetic flux current) and q-axis current (torque current) being orthogonal to each other. However, the controller 20 can control the motor 3 according to other model (control method). For example, even in a case of V/f control configured to be executed based on U-, V-, and W-phase current, or an induction motor in which the motor 3 can relatively easily obtain constant-output characteristics, the controller 20 can control the motor by the control method based on such a model.
The speed operator 21 arithmetically operates a rotation speed Ndet of the rotor 9 based on a rotor phase θ output from the position sensor 10, and outputs the rotation speed Ndet to the mode selector 22, the subtracter 23, and the constant-output controller 27. The speed operator 21 obtains the rotation speed Ndet, for example, by a change amount per unit time of the rotor phase θ.
The mode selector 22 selects a control mode from the first control mode and the second control mode based on the rotation speed Ndet. For example, the mode selector 22 selects the first control mode if the rotation speed Ndet is smaller than a set value Ns1, and selects the second control mode if the rotation speed Ndet is the set value Ns1 or greater. The mode selector 22 outputs information of the selected control mode to the speed controller 24, the constant-output controller 27, the motor-constant switch 28, and the gate-signal output unit 30.
Information indicative of the first control mode is, for example, a first mode signal SA with a logical value being “1” and a second mode signal SB with a logical value being “0.” Also, information indicative of the second control mode is, for example, a first mode signal SA with a logical value being “0” and a second mode signal SB with a logical value being “1.” The first mode signal SA and the second mode signal SB are each merely an example of information of a control mode, and hence the information is not limited to these signals. Hereinafter, the first mode signal SA and the second mode signal SB are collectively called mode signal SX1.
In the example of the mode selector 22 shown in
The subtracter 23 subtracts the rotation speed Ndet from a speed command N* output from a higher-order device (not shown), and outputs the subtraction result to the speed controller 24.
The speed controller 24 generates a q-axis current command Iq* so that the difference between the speed command N* and the rotation speed Ndet becomes zero, and outputs the q-axis current command Iq* to the gate-signal generator 29. The q-axis current command Iq* is a current command of a q-axis component in a d-q-axis rotation coordinate system synchronized with the rotor phase θ.
Also, the speed controller 24 can control the q-axis current (torque current) so that output effective power Pe is not changed before and after the switching between the first control mode and the second control mode. For example, the speed controller 24 limits the q-axis current command Iq* to a value multiplied by Nbase/Ns1 when the control mode is switched from the first control mode to the second control mode, so that the output effective power Pe is not changed before and after the switching of the control mode.
In contrast, the speed controller 24 multiplies the q-axis current command Iq* by Ns1/Nbase when the control mode is switched from the second control mode to the first control mode, so that the output effective power Pe is not changed before and after the switching of the control mode. The speed controller 24 detects a switching timing between the first control mode and the second control mode by a change in logical value of the mode signal SX1.
1.2.2.4. d-Axis Current Command Generator 25 and Subtracter 26
The d-axis current command generator 25 generates a d-axis current command Id**, and outputs the d-axis current command Id** to the subtracter 26. The d-axis current command Id** is, for example, zero if the motor 3 is a synchronous motor, and is, for example, a positive predetermined value if the motor 3 is an induction motor. The subtracter 26 subtracts a d-axis field weakening current command value Idrc output from the constant-output controller 27, from the d-axis current command Id**, and outputs a d-axis current command Id* being the subtraction result to the gate-signal generator 29.
The constant-output controller 27 generates the field weakening current command value Idrc corresponding to the rotation speed Ndet from the speed operator 21 and the logical value of the mode signal SX1 from the mode selector 22, and outputs the field weakening current command value Idrc to the subtracter 26. Alternatively, the field weakening current command value Idrc may be generated by using a motor constant from the motor-constant switch 28 (described later).
The field weakening current command value Idrc is substantially zero until the rotation speed Ndet of the motor 3 reaches a base rotation speed value Nbase. If the rotation speed Ndet exceeds the base rotation speed value Nbase, the constant-output controller 27 changes the field weakening current command value Idrc in a direction in which the field of the motor 3 is weakened in accordance with an increase in rotation speed Ndet.
Also, if the rotation speed Ndet of the motor 3 becomes the set value Ns1 and the control mode is switched from the first control mode to the second control mode, the constant-output controller 27 sets the field weakening current command value Idrc at substantial zero. If the rotation speed Ndet of the motor 3 exceeds the set value Ns1, the constant-output controller 27 changes the field weakening current command value Idrc in a direction in which the field of the motor 3 is weakened in accordance with an increase in rotation speed Ndet.
A region in which the rotation speed Ndet is lower than the base rotation speed value Nbase is occasionally called constant torque region, and a region in which the rotation speed Ndet is equal to or higher than the base rotation speed value Nbase is occasionally called constant output region. Also, the method of field weakening control is not limited to the method using the field weakening current command value Idrc, and may execute field weakening control by other known technology.
The motor-constant switch 28 outputs a motor constant corresponding to the control mode in accordance with the mode signal SX1 from the mode selector 22, to the speed controller 24 and the constant-output controller 27. In this case, a motor constant corresponding to a control mode is selected from a motor constant for the first control mode and a motor constant for the second control mode, in accordance with the mode signal SX. Accordingly, information of the motor constant used for generation of the q-axis current command Iq* in the speed controller 24 and generation of the field weakening current command value Idrc in the constant-output controller 27 can be properly switched. The information of the motor constant corresponds to each control mode, and is, for example, a torque-current conversion coefficient, a stator resistance, a d-axis inductance, a q-axis inductance, or a stator flux linkage.
The gate-signal generator 29 generates gate signals G1 to G6 based on the q-axis current command Iq* from the speed controller 24 and the d-axis current command Id* from the subtracter 26, and outputs the gate signals G1 to G6 to the gate-signal output unit 30.
To be specific, the gate-signal generator 29 generates current commands Iu*, Iv*, and Iw* of the U-phase, V-phase, and W-phase, based on the q-axis current command Iq*, the d-axis current command Id*, and the rotor phase θ. For example, the gate-signal generator 29 generates the current commands Iu*, Iv*, and Iw* according to arithmetic operations in Expressions (1) to (5).
I1=√{square root over (Id*2+Iq*2)} (1)
θi=tan−1(Iq*/Id*) (2)
Iu*=I1×sin(θ+θi) (3)
Iv*=I1×sin(θ+θi−120) (4)
Iw*=I1×sin(θ+θi−240) (5)
The gate-signal generator 29 generates line current commands Iuw*, Ivu*, and Iwv* from the current commands Iu*, Iv*, and Iw*. For example, the gate-signal generator 29 generates the current commands Iuw*, Ivu*, and Iwv* according to arithmetic operations in Expressions (6) to (8).
Iuw*=⅓(Iu*−Iw*) (6)
Ivu*=⅓(Iv*−Iu*) (7)
Iwv*=⅓(Iw*−Iv*) (8)
The gate-signal generator 29 generates the gate signals G1 to G6 based on the line current commands Iuw*, Ivu*, and Iwv*, and outputs the gate signals G1 to G6 to the gate-signal output unit 30. The generation of the gate signals G1 to G6 based on the line current commands Iuw*, Ivu*, and Iwv* is a known technology, and, for example, a technology disclosed in Japanese Unexamined Patent Application Publication No. 2012-196119 is used.
Now, the gate signals G1 to G6 are described. The gate-signal generator 29 generates the gate signals G1 to G6 equivalent to signals for controlling by PWM control and driving three-phase bridges (see
A current source inverter device 100 shown in
Now, the relationship between the gate signals G1 to G6 and current paths of current flowing through the motor 3 is described. The gate signals G1 to G6 are gate signals generated so that one of the upper switching elements Qp and one of the lower switching elements Qn are simultaneously in conduction. The combination of the switching elements Qp and Qn that are turned ON by the gate signals G1 to G6 is successively shifted as follows.
(Qpu, Qnv), (Qpu, Qnw), (Qpv, Qnw), (Qpv, Qnu), (Qpw, Qnu), and then (Qpw, Qnv).
To meet the successive shift, the path of current flowing through the motor 3 is shifted as follows.
Iuv, Iuw, Ivw, Ivu, Iwu, and then Iwv.
For example, Iuv indicates current flowing in the order from the positive DC bus P, the U-phase of the motor 3, the V-phase of the motor 3, and the negative DC bus N. Also, for example, Ivu indicates current flowing in the order from the positive DC bus P, the V-phase of the motor 3, the U-phase of the motor 3, and the negative DC bus N.
Also, with combinations of (Qpu, Qnu), (Qpv, Qnv), and (Qpw, Qnw), current paths that establish short circuits between the positive DC bus P and the negative DC bus N are formed. The current paths respectively correspond to current Iuu, Ivv, and Iww, and do not allow current to flow to the motor 3.
Next, the relationship between the above-described nine types of current paths and current vectors according to a space vector method is described.
Also,
The gate-signal generator 29 generates the gate signals G1 to G6 that successively shift the current vectors in the order of Iuv, Iuw, Ivw, Ivu, Iwu, and Iwv, based on the line current commands Iuw*, Ivu*, and Iwv* expressed in Expressions (6) to (8) provided above. The gate signals G1 to G6 are signals composed by the space vector method by using neighboring three types of vectors. The neighboring three types of vectors have combinations of, for example, (Iuw, Ivw, Iww), (Iwv, Iuv, Ivv), etc. The space vector method is known, and hence the detailed description is omitted.
The gate-signal output unit 30 generates gate signals G1u, G2u, G3u, G1v, G2v, G3v, G1w, G2w, and G3w (hereinafter, occasionally collectively called gate signal Gs) for driving the switching element Qs of the inverter 11 based on the gate signals G1 to G6. The gate signals G1u to G3u, G1v to G3v, and G1w to G3w respectively drive the switching elements Q1u to Q3u, Q1v to Q3v, and Q1w to Q3w.
According to the gate signal Gs output from the gate-signal output unit 30, one of the first and second three-phase windings 5 and 6 serves as a supply target of AC power in the first control mode, and both the first and second three-phase windings 5 and 6 serve as a supply target of AC power in the second control mode. Hereinafter, an example of a specific configuration of the gate-signal output unit 30 and control of the inverter 11 according to the gate signal Gs are successively described.
The U-phase signal output unit 31 generates the gate signals G1u, G2u, and G3u for controlling the U-phase switching elements Q1u, Q2u, and Q3u. The V-phase signal output unit 32 generates the gate signals G1v, G2v, and G3v for controlling the V-phase switching elements Q1v, Q2v, and Q3v. The W-phase signal output unit 33 generates the gate signals G1w, G2w, and G3w for controlling the W-phase switching elements Q1w, Q2w, and Q3w.
The U-phase signal output unit 31 includes logical AND operators (AND circuits) 41 and 42, and a logical OR operator (OR circuit) 43. The logical AND operator 41 outputs a logical AND of the gate signal G1 and the first mode signal SA. The logical AND operator 42 outputs a logical AND of the gate signal G4 and the second mode signal SB. The logical OR operator 43 outputs a logical OR of the output of the logical AND operator 41 and the output of the logical AND operator 42.
Since the first mode signal SA has the logical value of “1” and the second mode signal SB has the logical value of “0” in the first control mode, the U-phase signal output unit 31 outputs signals equivalent to the gate signal G1 as the gate signals G1u and G3u, and outputs a signal equivalent to the gate signal G4 as the gate signal G2u.
Also, since the first mode signal SA has the logical value of “0” and the second mode signal SB has the logical value of “1” in the second control mode, the U-phase signal output unit 31 outputs a signal equivalent to the gate signal G1 as the gate signal G1u, and outputs signals equivalent to the gate signal G4 as the gate signals G2u and G3u.
The V-phase signal output unit 32 has a configuration similar to the U-phase signal output unit 31. The V-phase signal output unit 32 outputs signals equivalent to the gate signal G2 as the gate signals G1v and G3v, and outputs a signal equivalent to the gate signal G5 as the gate signal G2v in the first control mode. Also, the V-phase signal output unit 32 outputs a signal equivalent to the gate signal G2 as the gate signal G1v, and outputs signals equivalent to the gate signal G5 as the gate signals G2v and G3v in the second control mode.
The W-phase signal output unit 33 has a configuration similar to the U-phase signal output unit 31. The W-phase signal output unit 33 outputs signals equivalent to the gate signal G3 as the gate signals G1w and G3w, and outputs a signal equivalent to the gate signal G6 as the gate signal G2w in the first control mode. Also, the W-phase signal output unit 33 outputs a signal equivalent to the gate signal G3 as the gate signal G1w, and outputs signals equivalent to the gate signal G6 as the gate signals G2w and G3w in the second control mode.
In the above-described embodiment, in the second control mode, current is supplied to the first three-phase winding 5; however, current may be supplied to the second three-phase winding 6 instead of the first three-phase winding 5. In this case, the U-phase signal output unit 31, the V-phase signal output unit 32, and the W-phase signal output unit 33 are configured, for example, as shown in
In the first control mode, for example, the U-phase signal output unit 31 shown in
When the first control mode is selected by the mode selector 22, the gate-signal output unit 30 generates the gate signal Gs for supplying AC power in series from the inverter 11 to each of the first and second three-phase windings 5 and 6, and outputs the gate signal Gs to the inverter 11.
In the first control mode, the pairs of the upper and lower switching elements Qp and Qn, specifically, (Q1u, Q3u), (Q1v and Q3v), and (Q1w, Q3w) are respectively driven by the gate signals G1, G2, and G3, and the middle switching elements Q2u, Q2v, and Q2w are respectively driven by the gate signals G4, G5, and G6.
The current Iuv passes through the V1 terminal TV1, the switching element Q2v and the V2 terminal TV2, and thus flows from the current source inverter device 2 to the second three-phase winding 6. The current Iuv passes through the V2-phase winding 6b and the U2-phase winding 6a in the second three-phase winding 6, and flows to the U2 terminal TU2 of the current source inverter device 2. The current Iuv passes through the U2 terminal TU2 and the switching element Q3u, and flows to the negative DC bus N.
As described above, in the first control mode, AC power is supplied in series from the inverter 11 to the first and second three-phase windings 5 and 6. Hence, the current source inverter device 2 can generate a relatively high counter voltage, and can provide a relatively high torque in the low-speed region, as compared with the current source inverter device 100.
In the first control mode, if the state is shifted from the current vector Iuv to the current vector Iuu, the gate-signal output unit 30 sets the logical value of the gate signal G2v at “0” and the logical value of the gate signal G2u at “1.” Accordingly, the switching element Q2v is turned OFF and the switching element Q3u is turned ON, and current is not supplied from the current source inverter device 2 to the motor 3.
In contrast, if the mode selector 22 selects the second control mode, the gate-signal output unit 30 generates the gate signal G2 so that AC power is supplied to only one three-phase winding of the first and second three-phase windings 5 and 6, and outputs the gate signal Gs to the inverter 11.
In the second control mode, the upper switching elements Q1u, Q1v, and Q1w are respectively driven by the gate signals G1, G2, and G3, and the pairs of the middle and lower switching elements Qp and Qn, specifically, (Q2u, Q3u), (Q2v and Q3v), and (Q2w, Q3w) are respectively driven by the gate signals G4, G5, and G6.
As described above, in the second control mode, AC power is supplied from the inverter 11 only to the first three-phase winding 5. Hence, the counter power of the motor 3 is halved as compared with the counter power in the first control mode. Accordingly, in the second control mode, the speed range can be expanded as compared with the first control mode.
In this way, in the current source inverter device 2, the control mode is switched in accordance with the rotation speed Ndet of the motor 3. Accordingly, the speed control range can be expanded for the motor 3.
As described above, in the current source inverter device 2 according to the first embodiment, the inverter 11 is configured such that 2+1 switching elements Qs are connected in series for each of the U-phase, V-phase, and W-phase of the motor 3, and two nodes among the switching elements Qs are respectively connected with different two windings with the same phase among the windings of the motor 3. The controller 20 includes the mode selector 22 that selects one or both of two windings per phase based on the rotation speed of the motor 3, as a supply target of AC power. Accordingly, in the current source inverter device 2, an induced voltage generated in the motor 3 can be reduced, and the speed control range can be expanded similarly to the winding switch method of the related art.
Next, a current source inverter device according to a second embodiment is described. The current source inverter device according to the second embodiment differs from the current source inverter device 2 according to the first embodiment in that a switching mode for the first control mode and the second control mode is provided. In the following description, points different from the motor driving system 1 according to the first embodiment are mainly described, and components having similar functions to those of the first embodiment are given with the same reference signs and redundant description is omitted.
As shown in
The mode selector 22A generates a first mode signal SA and a second mode signal SB with ON ratios corresponding to a rotation speed Ndet output from the speed operator 21, and outputs the first mode signal SA and the second mode signal SB, to the gate-signal output unit 30. The mode selector 22A, as a first selection command unit, selects a first control mode if Ndet<Nbase, and selects a second control mode if Ns1<Ndet. The ON ratio is a ratio with which the logical value becomes “1” for a predetermined unit time (for example, carrier period Tc, described later).
Also, the mode selector 22A, as a second selection command unit, may alternately switch the control mode between the first control mode and the second control mode with the time ratio corresponding to the rotation speed Ndet if Nbase≦Ndet<Ns1. In the mode selector 22A, the first selection command unit and the second selection command unit have the same configuration; however, the first selection command unit and the second selection command unit may have different configurations or partly common configurations. The time ratio is a temporal ratio with which the first control mode and the second control mode are selected in a predetermined unit time (for example, carrier period Tc, described later).
The carrier-signal generator 51 generates a carrier signal Sc with a predetermined period and outputs the carrier signal Sc. The carrier signal Sc is, for example, a triangular waveform signal or a saw waveform signal. The period of the carrier signal Sc is desirably a value p (p being a natural number) times a generation period of the gate signals G1 to G6 output from the gate-signal generator 29 with regard to the turn ON and OFF periods of the switching element Qs, and is desirably synchronized with the gate signals G1 to G6.
The modulation-signal generator 52 generates a modulation signal Sm having a magnitude corresponding to the rotation speed Ndet output from the speed operator 21.
The comparator 53 compares the carrier signal Sc with the modulation signal Sm, and generates the second mode signal SB. To be specific, the comparator 53 outputs the first mode signal SA having the logical value being “1” if the modulation signal Sm is smaller than the carrier signal Sc, and the comparator 53 outputs the second mode signal SB having the logical value being “0” if the modulation signal Sm is equal to or greater than the carrier signal Sc. The logical NOT operator 54 receives an input of the first mode signal SA, and outputs the second mode signal SB, in which the logical value of the first mode signal SA is inverted.
Hence, if Nbase≦Ndet<Ns1, the time ratio with which the logical value of the first mode signal SA becomes “1” is expressed by T1/Tc, and the time ratio with which the logical value of the second mode signal SB becomes “1” is expressed by T2/Tc. Accordingly, the current source inverter device 2A executes the switching mode in which the first control mode and the second control mode are alternately turned ON and OFF if Nbase≦Ndet<Ns1.
In contrast, the magnitude of the modulation signal Sm is “0” if Ndet<Nbase, and the magnitude of the modulation signal Sm is “1” if Ns1≦Ndet. Hence, the current source inverter device 2A operates in the first control mode if Ndet<Nbase, and operates in the second control mode if Ns1≦Ndet.
The speed controller 24A (
The constant-output controller 27A (
With such control, in the current source inverter device 2A, the motor 3 can be operated equivalently to a case that a motor, the characteristic of which is changed as shown in
As described above, since the current source inverter device 2A executes the switching control in which the number of windings for supplying AC power is switched every phase of the motor 3, the speed control range can be expanded and the high efficiency region can be expanded.
Next, a current source inverter device according to a third embodiment is described. The current source inverter devices 2 and 2A of the first and second embodiments each operate in the first and second control modes; however, the current source inverter device according to the third embodiment operates in a third control mode in addition to the first and second control modes. In the following description, points different from the motor driving system 1 according to the first embodiment are mainly described, and components having similar functions to those of the first embodiment are given with the same reference signs and redundant description is omitted.
The current source inverter device 2B includes an inverter 11 and a controller 20B. The inverter 11 has a configuration similar to the inverter 11 according to the first embodiment. In contrast, the controller 20B differs from the controller 20 in that the controller 20B executes the third control mode in addition to the first and second control modes.
Also, the motor 3B differs from the motor 3 in that the number of windings of a first three-phase winding 5B is twice the number of windings of a second three-phase winding 6B. That is, windings 5Ba to 5Bc each have a number of windings that is twice the number of windings of each of windings 6Ba to 6Bc.
The controller 20B supplies power to the first and second three-phase windings 5B and 6B in the first control mode. The controller 20B supplies power to the first three-phase winding 5B in the second control mode. The controller 20B supplies power to the second three-phase winding 6B in the third control mode.
Accordingly, when current of the same value is applied to the motor 3B, the induced voltage in the second control mode becomes 2/3 as compared with the first control mode, and the induced voltage in the third control mode becomes 1/3 as compared with the first control mode. Hence, with the current source inverter device 2B, the speed control range can be further expanded as compared with the current source inverter device 2.
The mode selector 22B selects one control mode from the first to third control modes based on a rotation speed Ndet and set values Ns1 and Ns2. To be specific, the mode selector 22B selects the first control mode if Ndet<Ns1, selects the second control mode if Ns1≦Ndet<Ns2, and selects the third control mode if Ns2≦Ndet. The mode selector 22B outputs information of the selected control mode to the speed controller 24B, the constant-output controller 27B, the motor-constant switch 28B, and the gate-signal output unit 30B.
Information indicative of the first control mode is, for example, a first mode signal SA with a logical value being “1,” and second and third mode signals SB and SC with logical values being “0.” Also, information indicative of the second control mode is, for example, the first and third mode signal SA and SC with logical values being “0” and the second mode signal SB with a logical value being “1.” Also, information indicative of the third control mode is, for example, the third mode signal SC with a logical value being “1” and the first and second mode signals SA and SB with logical values being “0.”
The first to third mode signals SA, SB, and SC are each merely an example of information of a control mode, and hence the information is not limited to these signals. Hereinafter, the first to third mode signals SA, SB, and SC are collectively written as mode signal SX2.
The speed controller 24B generates a q-axis current command Iq* so that the difference between a speed command N* and a rotation speed Ndet becomes zero, and outputs the q-axis current command Iq* to the gate-signal generator 29. The speed controller 24B holds the q-axis current command Iq* constant similarly to the speed controller 24 if field weakening control is being executed by the constant-output controller 27B. Also, the speed controller 24B can control q-axis current (torque current) so that output effective power Pe is not changed before and after the switching of the control mode similarly to the speed controller 24.
The constant-output controller 27B generates a field weakening current command value Idrc corresponding to the rotation speed Ndet from the speed operator 21 and the logical value of the mode signal SX2 from the mode selector 22B, and outputs the field weakening current command value Idrc to the subtracter 26. For example, the constant-output controller 27B sets the field weakening current command value Idrc at substantially zero at the switching from the first control mode to the second control mode and at the switching from the second control mode to the third control mode. The constant-output controller 27B changes the field weakening current command value Idrc in a direction in which the field of the motor 3B is weakened in accordance with an increase in rotation speed Ndet.
The motor-constant switch 28B selects a motor constant of a control mode corresponding to the mode signal SX2 among motor constants for the first to third control modes, in accordance with the mode signal SX2 from the mode selector 22B, and outputs the motor constant to the speed controller 24B and the constant-output controller 27B. Accordingly, information of the motor constant used for generation of the q-axis current command Iq* in the speed controller 24B and generation of the field weakening current command value Idrc in the constant-output controller 27B can be properly switched.
The gate-signal output unit 30B generates a gate signal Gs from the gate signals G1 to G6, in accordance with the mode signal SX2 from the mode selector 22B. With this gate signal Gs, the first and second three-phase windings 5B and 6B become supply targets of AC power in the first control mode, the first three-phase winding 5B becomes a supply target of AC power in the second control mode, and the second three-phase winding 6B becomes a supply target of AC power in the third control mode.
The U-phase signal output unit 31B includes logical AND operators 61 to 66, and logical OR circuits 67 and 68. The logical AND operators 61 and 64 each output a logical AND of the gate signal G1 and the first mode signal SA. The logical AND operator 62 outputs a logical AND of the gate signal G1 and the second mode signal SB. The logical AND operator 63 outputs a logical AND of the gate signal G4 and the third mode signal SC.
The logical AND operator 65 outputs a logical AND of the gate signal G4 and the second mode signal SB. The logical AND operator 66 outputs a logical AND of the gate signal G1 and the third mode signal SC. The logical OR circuit 67 outputs a logical OR of outputs of the logical AND operators 61 to 63. The logical OR circuit 68 outputs a logical OR of outputs of the logical AND operators 64 to 66.
In the first control mode, the logical values of the first to third mode signals SA to SC are respectively “1,” “0,” and “0.” Hence, the U-phase signal output unit 31B outputs signals equivalent to the gate signal G1 as the gate signals G1u and G3u, and outputs a signal equivalent to the gate signal G4 as the gate signal G2u.
In the second control mode, the logical values of the first to third mode signals SA to SC are respectively “0,” “1,” and “0.” Hence, the U-phase signal output unit 31B outputs a signal equivalent to the gate signal G1 as the gate signal G1u, and outputs signals equivalent to the gate signal G4 as the gate signals G2u and G3u.
In the third control mode, the logical values of the first to third mode signals SA to SC are respectively “0,” “0,” and “1.” Hence, the U-phase signal output unit 31B outputs a signal equivalent to the gate signal G1 as the gate signal G3u, and outputs signals equivalent to the gate signal G4 as the gate signals G1u and G2u.
The V-phase signal output unit 32B has a configuration similar to the U-phase signal output unit 31B. The V-phase signal output unit 32B outputs signals equivalent to the gate signal G2 as the gate signals G1v and G3v, and outputs a signal equivalent to the gate signal G5 as the gate signal G2v in the first control mode. Also, the V-phase signal output unit 32B outputs a signal equivalent to the gate signal G2 as the gate signal G1v, and outputs signals equivalent to the gate signal G5 as the gate signals G2v and G3v in the second control mode. Also, the V-phase signal output unit 32B outputs a signal equivalent to the gate signal G2 as the gate signal G3v, and outputs signals equivalent to the gate signal G5 as the gate signals G1v and G2v in the third control mode.
The W-phase signal output unit 33B has a configuration similar to the U-phase signal output unit 31B. The W-phase signal output unit 33B outputs signals equivalent to the gate signal G3 as the gate signals G1w and G3w, and outputs a signal equivalent to the gate signal G6 as the gate signal G2w in the first control mode. Also, the W-phase signal output unit 33B outputs a signal equivalent to the gate signal G3 as the gate signal G1w, and outputs signals equivalent to the gate signal G6 as the gate signals G2w and G3w in the second control mode. Also, the W-phase signal output unit 33B outputs a signal equivalent to the gate signal G3 as the gate signal G3w, and outputs signals equivalent to the gate signal G6 as the gate signals G1w and G2w in the third control mode. In
As described above, the motor driving system 1B according to the third embodiment includes the motor 3B having the first and second three-phase windings 5B and 6B, the numbers of windings being different from each other. The controller 20B selects a supply target of AC power per phase based on the speed of the motor 3B. That is, the controller 20B sets the supply target(s) of AC power at the first and second three-phase windings 5B and 6B in the first control mode, at the first three-phase winding 5B in the second control mode, and at the second three-phase winding 6B in the third control mode. Accordingly, in the current source inverter device 2B, the induced voltage generated in the motor 3B can be reduced by two steps, and the speed control range can be further expanded.
Next, a current source inverter device according to a fourth embodiment is described. The current source inverter devices 2, 2A, and 2B according to the first to third embodiments operate the motors 3 and 3B each having two windings per phase. However, the current source inverter device according to the fourth embodiment operates a motor having four windings per phase. In the following description, points different from the motor driving system 1 according to the first embodiment are mainly described, and components having similar functions to those of the first embodiment are given with the same reference signs and redundant description is omitted.
The motor 3C is a three-phase quadruple-winding motor formed of quadruple windings in which stator windings are insulated from each other, and has first to fourth three-phase windings 5C to 8C. The three-phase windings 5C to 8C have the same number of windings. However, the numbers of windings may be different from each other like the motor 3B according to the third embodiment.
Respective windings 5Ca, 5Cb, and 5Cc of the first three-phase winging 5C and respective windings 7Ca, 7Cb, and 7Cc of the third three-phase winding 7C have the same polarity. Respective windings 6Ca, 6Cb, and 6Cc of the second three-phase winging 6C and respective windings 8Ca, 8Cb, and 8Cc of the fourth three-phase winding 8C have the same polarity. To be specific, the four windings corresponding to each phase of the motor 3C are inserted into the same slot of the stator, are electromagnetically densely coupled to each other, and have winding directions with alternately reversed polarities. In
The current source inverter device 2C includes terminals TU1, TU2, TV1, TV2, TW1, TW2, TU3, TU4, TV3, TV4, TW3, and TW4, an inverter 11C, and a controller 20C.
The terminals TU1, TV1, and TW1 are connected with the first three-phase winding 5C included in the motor 3C. The terminals TU2, TV2, and TW2 are connected with the second three-phase winding 6C included in the motor 3C. Also, the terminals TU3, TV3, and TW3 are connected with the third three-phase winding 7C included in the motor 3C. The terminals TU4, TV4, and TW4 are connected with the fourth three-phase winding 8C included in the motor 3C.
The inverter 11C includes a switching element unit 12C, and filters 16a to 16d. The switching element unit 12C includes switching element units 13C to 15C. The switching element unit 13C is provided for the U-phase of the motor 3C. The switching element unit 14C is provided for the V-phase of the motor 3C. The switching element unit 15C is provided for the W-phase of the motor 3C.
The switching element units 13C to 15C each have five switching elements connected in series. To be specific, the switching element unit 13C is formed such that five switching elements Q1u to Q5u are connected in series. The switching element unit 14C is formed such that five switching elements Q1v to Q5v are connected in series. Also, the switching element unit 15C is formed such that five switching elements Q1w to Q5w are connected in series.
The switching elements Q4u, Q5u, Q4v, Q5v, Q4w, and Q5w have configurations similar to the switching element Q1u or the like. Hereinafter, these switching elements may be occasionally collectively called switching element Qs.
The switching element units 13C to 15C each have four nodes among the switching elements Qs, and the four nodes are respectively connected with different four windings with the same phase of the motor 3C. To be specific, regarding the switching element unit 13C, nodes N1u, N2u, N3u, and N4u are respectively connected with a U1-phase, a U2-phase, a U3-phase, and a U4-phase of the motor 3C. Regarding the switching element unit 14C, nodes N1v, N2v, N3v, and N4v are respectively connected with a V1-phase, a V2-phase, a V3-phase, and a V4-phase of the motor 3C. Regarding the switching element unit 15C, nodes N1w, N2w, N3w, and N4w are respectively connected with a W1-phase, a W2-phase, a W3-phase, and a W4-phase of the motor 3C.
The filter 16a and the filter 16b have configurations similar to the first embodiment. One ends of capacitors of the filter 16c are respectively connected with the terminals TU3, TV3, and TW3, and the other ends of the capacitors are commonly connected. One ends of capacitors of the filter 16d are respectively connected with the terminals TU4, TV4, and TW4, and the other ends of the capacitors are commonly connected. With the filters 16a to 16d, high-frequency components of current output from the switching element units 13C to 15C of respective phases are removed.
The controller 20C generates a gate signal in a control mode corresponding to the rotation speed of the motor 3C among first to fourth control modes, and outputs the gate signal to the inverter 11C. The controller 20C supplies AC power to four windings per phase of the motor 3C in the first control mode, and supplies AC power to three windings per phase of the motor 3C in the second control mode. The controller 20C supplies AC power to two windings per phase of the motor 3C in the third control mode, and supplies AC power to one winding per phase of the motor 3C in the fourth control mode.
The controller 20C switches the control mode from the first control mode to the second control mode, the third control mode, and then the fourth control mode as the rotation speed of the motor 3C increases, and thus executes switching for reducing the induced voltage of the motor 3C. Accordingly, the current source inverter device 2C can expand the speed control range.
The mode selector 22C selects one control mode from the first to fourth control modes based on a rotation speed Ndet and set values Ns1, Ns2, and Ns3. To be specific, the mode selector 22C selects the first control mode if Ndet<Ns1, and selects the second control mode if Ns1≦Ndet<Ns2. Also, the mode selector 22C selects the third control mode if Ns2≦Ndet<Ns3, and selects the fourth control mode if Ns3≦Ndet.
Information indicative of the first control mode is, for example, a first mode signal SA with a logical value being “1,” and second to fourth mode signals SB, SC, and SD with logical values being “0.” Also, information indicative of the second control mode is, for example, the second mode signal SB with a logical value being “1” and the first, third, and fourth mode signals SA, SC, and SD with logical values being “0.” Also, information indicative of the third control mode is, for example, the third mode signal SC with a logical value being “1” and the first, second, and fourth mode signals SA, SB, and SD with logical values being “1.” Also, information indicative of the fourth control mode is, for example, the fourth mode signal SD with a logical value being “1” and the first to third mode signals SA, SB, and SC with logical values being “1.”
The first to fourth mode signals SA, SB, SC, and SD are each merely an example of information of a control mode, and hence the information is not limited to these signals. Hereinafter, the first to fourth mode signals SA, SB, SC, and SD are collectively written as mode signal SX3.
In the example of the mode selector 22C shown in
The speed controller 24C generates a q-axis current command Iq* so that the difference between a speed command N* and the rotation speed Ndet becomes zero, and outputs the q-axis current command Iq* to the gate-signal generator 29. The speed controller 24C holds the q-axis current command Iq* constant similarly to the speed controller 24 if field weakening control is executed by the constant-output controller 27C. Also, the speed controller 24C can control q-axis current (torque current) so that output effective power Pe is not changed before and after the switching of the control mode similarly to the speed controller 24.
The constant-output controller 27C generates a field weakening current command value Idrc corresponding to the rotation speed Ndet from the speed operator 21 and the logical value of the mode signal SX3 from the mode selector 22C, and outputs the field weakening current command value Idrc to the subtracter 26. For example, the constant-output controller 27C sets the field weakening current command value Idrc at substantially zero at the switching from the first control mode to the second control mode, at the switching from the second control mode to the third control mode, and at the switching from the third control mode to the fourth control mode. The constant-output controller 27C changes the field weakening current command value Idrc in a direction in which the field of the motor 3C is weakened in accordance with an increase in rotation speed Ndet.
The motor-constant switch 28C selects a motor constant of a corresponding control mode among motor constants for the first to fourth control modes, in accordance with the mode signal SX3 from the mode selector 22C, and outputs the motor constant to the speed controller 24C and the constant-output controller 27C. Accordingly, information of the motor constant used for generation of the q-axis current command Iq* in the speed controller 24C and generation of the field weakening current command value Idrc in the constant-output controller 27C can be properly switched.
The gate-signal output unit 30C generates gate signals G1u to G5u, G1v to G5v, and G1w to G5w (hereinafter, occasionally collectively called gate signal Gs) for driving the switching element Qs of the inverter 11C in accordance with the mode signal SX3 from the mode selector 22C. The gate signals G1u to G5u, G1v to G5v, and G1w to G5w respectively drive the switching elements Q1u to Q5u, Q1v to Q5v, and Q1w to Q5w.
When the first control mode is selected by the mode selector 22C, the gate-signal output unit 30C generates the gate signal Gs for supplying AC power in series from the inverter 11C to each of the first to fourth three-phase windings 5C to 80, and outputs the gate signal Gs to the inverter 11C.
In the first control mode, the upper-middle and lower-middle switching elements Q2u, Q2v, Q2w, Q4u, Q4v, and Q4w are driven by the corresponding gate signals G4, G5, and G6, and the other switching elements Qs are driven by the corresponding gate signals G1, G2, and G3. Accordingly, AC power is supplied from the inverter 11C to the first to fourth three-phase windings 5C to 8C. For example, when the current Iuv is applied in the first control mode, the gate-signal output unit 30C outputs the gate signals G1u, G2v, G3u, G4v, and G5u with logical values being “1,” and outputs the other gate signals Gs with logical values being “0.”
Also, in the second control mode, the upper-middle, lower-middle, and lowermost switching elements Q2u, Q2v, Q2w, Q4u, Q4v, Q4w, Q5u, Q5v, and Q5w are driven by the corresponding gate signals G4, G5, and G6, and the other switching elements Qs are driven by the corresponding gate signals G1, G2, and G3. Accordingly, AC power is supplied from the inverter 11C only to the first to third three-phase windings 5C to 7C. For example, when the current Iuv is applied in the second control mode, the gate-signal output unit 30C outputs the gate signals G1u, G2v, G3u, G4v, and G5v with logical values being “1,” and outputs the other gate signals Gs with logical values being “0.”
Also, in the third control mode, the upper-middle switching elements Q2u, Q2v, and Q2w are driven by the corresponding gate signals G4, G5, and G6, and the other switching elements Qs are driven by the corresponding gate signals G1, G2, and G3. Accordingly, AC power is supplied from the inverter 11C only to the first and second three-phase windings 5C and 6C. For example, when the current Iuv is applied in the third control mode, the gate-signal output unit 30C outputs the gate signals G1u, G2v, and G3u to G5u with logical values being “1,” and outputs the other gate signals Gs with logical values being “0.”
In the fourth control mode, the uppermost switching elements Q1u, Q1v, and Q1w are driven by the corresponding gate signals G1, G2, and G3, and the other switching elements Qs are driven by the corresponding gate signals G4, G5, and G6. Accordingly, AC power is supplied from the inverter 11C only to the first three-phase winding 5C. For example, when the current Iuv is applied in the fourth control mode, the gate-signal output unit 30C outputs the gate signals G1u, and G2v to G5v with logical values being “1,” and outputs the other gate signals Gs with logical values being “0.”
It is to be noted that the configuration of the gate-signal output unit 30C is not limited to the above-described configuration as long as the gate-signal output unit 30C can supply AC power individually to windings in accordance with the control mode. For example, the gate-signal output unit 30C may cause the switching elements Q1u to Q4u, Q1v to Q4v, and Q1w to Q4w except the lowermost switching elements to be driven by the corresponding gate signals G1, G2, and G3, and the lowermost switching elements Q5u, Q5v, and Q5w may be driven by the corresponding gate signals G4, G5, and G6.
As described above, the current source inverter device 2C switches the control mode from the first control mode to the second control mode, the third control mode, and then the fourth control mode as the rotation speed of the motor 3C increases, and thus executes switching for reducing the induced voltage of the motor 3C. Accordingly, the current source inverter device 2C can expand the speed control range.
If a switching unit is formed by connecting a number n+1 (n being an integer of 2 or greater) of switching elements Qs in series per phase, a motor having a number m of windings per phase can be controlled. The control target is not limited to the motor 3, 3C having two or four windings per phase, and the control target may be a motor having three, or five or more windings per phase.
Next, a current source inverter device according to a fifth embodiment is described. The current source inverter devices 2, and 2A to 2C according to the above-described embodiments operate the motors 3, 3B, and 3C each having a number m (m being an integer of 2 or greater) of windings per phase. However, the current source inverter device according to the fifth embodiment operates a number n (n being an integer of 2 or greater) of motors each having the number m of windings per phase. In the following description, points different from the motor driving system 1C according to the fourth embodiment are mainly described based on m=4 and n=2, and components having similar functions to those of the fourth embodiment are given with the same reference signs and redundant description is omitted.
The current source inverter device 2D synchronizes the two motors 3D and 3E at the same speed and controls the motors 3D and 3E. Control of the motors 3D and 3E by the current source inverter device 2D is similar to the control of the motor 3 by the current source inverter device 2.
An inverter 11C and a controller 20D are provided. The inverter 11C has a configuration similar to the inverter 11C according to the fourth embodiment. The controller 20D controls the inverter 11C in one operation mode of first and second control modes.
When the first control mode is selected by the mode selector 22, the gate-signal output unit 30D generates the gate signal Gs for supplying AC power in series from the inverter 11C to three-phase windings 5 and 6 of each of the two motors 3D and 3E, and outputs the gate signal Gs to the inverter 11C.
In the first control mode, the upper-middle and lower-middle switching elements Q2u, Q2v, Q2w, Q4u, Q4v, and Q4w are driven by the corresponding gate signals G4, G5, and G6, and the other switching elements Qs are driven by the corresponding gate signals G1, G2, and G3. Accordingly, AC power is supplied from the inverter 11C to the two three-phase windings 5 and 6 of each of the motors 3D and 3E. For example, when current Iuv is applied in the first control mode, the gate-signal output unit 30D outputs the gate signals G1u, G2v, G3u, G4v, and G5u with logical values being “1,” and outputs the other gate signals Gs with logical values being “0.”
Also, in the second control mode, the upper-middle and middle switching elements Q2u, Q2v, Q2w, Q3u, Q3v, and Q3w are driven by the corresponding gate signals G4, G5, and G6, and the other switching elements Qs are driven by the corresponding gate signals G1, G2, and G3. Accordingly, AC power is supplied from the inverter 11C only to the three-phase windings 5 of the motors 3D and 3E. For example, when the current Iuv is applied in the third control mode, the gate-signal output unit 30D outputs the gate signals G1u, G2v, G3v, G4u, and G5u with logical values being “1,” and outputs the other gate signals Gs with logical values being “0.”
The gate-signal output unit 30D may also generate the gate signals G1u to G5u, G1v to G5v, and G1w to G5w to supply AC power from the inverter 11C only to the second three-phase windings 6 of the motors 3D and 3E in the second control mode.
As described above, the current source inverter device 2D according to the fifth embodiment can expand the speed control range while operating the two motors 3D and 3E each having two windings per phase. If a switching unit is formed by connecting a number n×m+1 (n, m each being integers of 2 or greater) of switching elements in series, a number n of motors each having a number m of windings per phase can be controlled. The control target is not limited to the two motors 3D and 3E each having the two windings per phase.
In the motor driving system 1D according to the fifth embodiment, the current source inverter device 2D may alternately switch the three-phase windings, as a supply target of AC power, between the three-phase windings of the motor 3D and the three-phase windings of the motor 3E every predetermined period. Accordingly, the current and torque of the two motors 3D and 3E can be balanced. By increasing or decreasing the number of three-phase windings to be selected as the supply target of AC power, torque control and speed control in wide ranges can be executed.
For example, in the motor driving system 1D according to the fifth embodiment, the current source inverter device 2D may alternately switch a combination of three three-phase windings as a supply target of AC power among different combinations of three-phase windings every predetermined period. For example, the controller 20D supplies AC power to the first and second three-phase windings 5 and 6 of the motor 3D and the first three-phase winding 5 of the motor 3E in the first control mode, and the controller 20D supplies AC power to the first three-phase winding 5 of the motor 3D and the first and second three-phase windings 5 and 6 of the motor 3E in the second control mode. The controller 20D alternately switches the control mode between the first control mode and the second control mode every predetermined period, so as to equalize average currents and average torques applied to the two motors 3D and 3E. In this case, in the controller 20D, the gate-signal output unit 30D switches a combination of three three-phase windings among different combinations as a supply target of AC power in accordance with the control mode. Also, in the controller 20D, the mode selector 22 outputs the first mode signal SA and the second mode signal SB with the ON ratio of 50%.
Also, in the motor driving system 10 according to the fifth embodiment, the current source inverter device 2D may alternately switch a motor as a supply target of AC power between the motor 3D and the motor 3E every predetermined period. For example, the controller 20D supplies AC power to the first and second three-phase windings 5 and 6 of the motor 3D in the first control mode, and the controller 20D supplies AC power to the first and second three-phase windings 5 and 6 of the motor 3E in the second control mode. The controller 20D alternately switches the control mode between the first control mode and the second control mode every predetermined period, so as to equalize average currents and average torques applied to the two motors 3D and 3E. In this case, in the controller 20D, the gate-signal output unit 30D switches a motor between the motor 3D and the motor 3E as a supply target of AC power in accordance with the control mode. Also, in the controller 20D, the mode selector 22 outputs the first mode signal SA and the second mode signal SB with the ON ratio of 50%.
Also, in the motor driving system 1D according to the fifth embodiment, the current source inverter device 2D may alternately switch a motor as a supply target of AC power between a single three-phase winding of the motor 3D and a single three-phase winding of the motor 3E every predetermined period. For example, the controller 20D supplies AC power to the first three-phase winding 5 of the motor 3D in the first control mode, and the controller 200 supplies AC power to the first three-phase winding 5 of the motor 3E in the second control mode. The controller 20D alternately switches the control mode between the first control mode and the second control mode every predetermined period, so as to equalize average currents and average torques applied to the two motors 3D and 3E. In this case, in the controller 20D, the gate-signal output unit 30D switches a three-phase winding between a single three-phase winding of the motor 3D and a single three-phase winding of the motor 3E as a supply target of AC power in accordance with the control mode. Also, in the controller 20D, the mode selector 22 outputs the first mode signal SA and the second mode signal SB with the ON ratio of 50%.
In the above-described examples of the third to fifth embodiments, the change points from the current source inverter device 2 according to the first embodiment have been described. However, by performing similar processing as the processing of the current source inverter device 2A according to the second embodiment, the high efficiency region can be expanded.
Also, in the above description, the controllers 20, and 20A to 20D are each described as a unit that controls a motor 3 in a constant torque region and a constant output region. However, control only in the constant torque region can be performed. In this case, for example, the controllers 20, and 20A to 20D each may control the motor 3 according to a desired purpose of use including a large torque at low speed or when stopped and performance of high-speed operation.
Further advantages and modifications can be easily derived by those skilled in the art. Hence, a more broad aspect of the disclosure is not limited to the specific details and representative embodiments expressed and described above.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-212025 | Oct 2013 | JP | national |
