Patent Application
20240290556
The present disclosure relates to a switch unit having an on-load tap changer and having a drive unit, and to a method for carrying out a switchover by means of the switch unit.
On-load tap-changers usually have a diverter switch and a selector. The actuation of the on-load tap changer is usually realized by means of a motor-drive unit in conjunction with a spring energy store. When a switchover is carried out, the motor-drive unit prestresses the springs of the spring energy store. In this case, either compression springs are compressed or tension springs are extended. From a defined mechanical point, the energy introduced into the springs is abruptly released and the on-load tap changer is actuated. For this type of actuation, there is no possibility for the energy required for the switchover, at least from the point in time at which the spring energy is released, to be controlled.
In an embodiment, the present disclosure provides a switch unit for switching over an onload tap changer. The switch unit has an on-load tap changer with an actuating shaft that actuates a switch; and a drive system with a motor. The drive system is mechanically coupled to and configured to actuate the on-load tap changer. The drive system is configured such that, when the on-load tap changer is actuated, the drive system uses the actuating shaft as a store for kinetic energy in such a way that the actuating shaft is accelerated and the switch is actuated by the kinetic energy from the actuating shaft and additional energy provided by the motor.
Subject matter of the present disclosure will be described in even greater detail below based on the exemplary figures. All features described and/or illustrated herein can be used alone or combined in different combinations. The features and advantages of various embodiments will become apparent by reading the following detailed description with reference to the attached drawings, which illustrate the following:
Aspects of the present disclosure provide a switch unit without a spring energy store that intelligently uses the energy required for the switchover and, at the same time, is of simple and compact construction.
Further aspects of the present disclosure provide a method for carrying out a switchover by means of the switch unit that is able to be carried out reliably and efficiently.
According to a first aspect, the present disclosure proposes a switching unit comprising:
The switch unit according to the present disclosure makes it possible for the switching means to be actuated particularly efficiently and thus for a switchover of the on-load tap changer to be carried out. The actuating shaft is initially accelerated and absorbs kinetic energy. During this phase, although the actuating shaft is mechanically connected to the switching means, it does not actuate them yet. The switching means are actuated only from a point, which is defined by the construction. Here, the kinetic energy of the actuating shaft and the energy from the motor of the drive system are then used to actuate the switching means and thus to carry out a switchover of the on-load tap changer. The mass of the actuating shaft and the motor of the drive system are optimally matched to the switching means. Consequently, when the switching means are actuated, a situation in which the rotational speed of the motor falls such that a minimum value of the rotational speed is fallen below is avoided. In this way, switching times are adhered to at all times. Transition resistors are not acted on by a circulating current for too long. Furthermore, use is made of a motor which is precisely adapted and which is not overdimensioned. The switch unit is thus economical. The momentum of the actuating shaft is used for optimally carrying out a diverter switch operation.
The switch unit may be of any desired design, wherein the actuating shaft and the switching means are mechanically coupled in such a way that the actuating shaft actuates the switching means after a fixed angle of rotation.
In this case, the actuating shaft may have on its outer surface cams which are distributed in a partially encircling manner. The switch unit may have multiple switching means which comprise vacuum interrupters and/or selector contacts. The switching means could comprise actuating levers which travel over the outer surface of the actuating shaft by means of rolls. During the rotation of the actuating shaft, the switching means are actuated only when the respective roll of an actuating lever meets a cam. When actuated, the vacuum interrupters are correspondingly closed and opened. The selector contacts contact the fixed contacts, which are connected to step taps of a tap winding.
The switch unit may be of any desired design, wherein the actuating shaft is revolved at least once, and the motor shaft is revolved multiple times, when the on-load tap changer is actuated.
When a switchover is being carried out, the motor shaft revolves multiple times according to the embodiment of a gear unit between the motor and the actuating shaft. During a switchover, the actuating shaft revolves at least once and at most three times, that is to say at least through 360 degrees or at most through 1080 degrees.
The switch unit may be of any desired design, wherein a torque for accelerating the actuating shaft is approximately or greater than a torque by which the switch means is/are actuated.
According to a second aspect, the present disclosure proposes a method for carrying out a switchover by means of a switch unit, wherein:
In carrying out a switchover by means of the switching unit, in particular in carrying out a switchover of the on-load tap changer or the actuation thereof, the switching process may be divided into multiple steps. In a first step, the actuating shaft is accelerated by the motor of the drive system. In the process, the actuating shaft stores kinetic energy. In a second step, the switching means are actuated. The energy required for this purpose is taken from the kinetic energy of the actuating shaft and further energy from the motor of the drive system.
The encoder system 13 is configured to detect a first value for a position, such as for example an angular position, in particular an absolute angular position, of the drive shaft 16 and thus also of the actuating shaft 20. For this purpose, the encoder system 13 may comprise for example an absolute-value encoder, in particular a multi-turn absolute-value encoder, or a single-turn rotary encoder, which is fastened to the drive shaft 16, the motor shaft 14 or some other shaft whose position is unambiguously linked to the position of the drive shaft 16. For example, the position of the drive shaft 16 or actuating shaft 20 is able to be determined unambiguously from the position of the motor shaft 14, such as for example via a transmission ratio of the gear unit 15. Furthermore, the encoder system 13 may comprise a virtual rotary encoder which determines the position of the motor shaft 14 and, from this, deduces the position of the drive shaft 16 or the actuating shaft 20.
The feedback system 4 is configured to detect a value for the position of the drive shaft 16 and thus also a position of the actuating shaft 20. In the case of an encoder system 13 designed as a multi-turn absolute-value encoder or a single-turn rotary encoder, the value for the position of the drive shaft 16 is made available as a protocol.
In the case of the encoder system 13 being designed as a virtual rotary encoder, the value for the position of the drive shaft 16 is ascertained from a rotor position of the motor 12. For this purpose, for example, an inductive feedback may be utilized by the movement of the rotor in motor windings of the motor 12. Since a strength of the feedback varies periodically, it is possible, in particular by means of signal analysis, such as for example by way of FFT analysis, for the rotor position to be determined approximately. Since one full revolution of the drive shaft 16 corresponds to a plurality of revolutions of the rotor, the position of the drive shaft 16 and also of the actuating shaft 20 can be deduced therefrom with much higher accuracy.
The encoder system 13 may also be designed as a combination of a virtual rotary encoder and an auxiliary contact which is connected directly or indirectly to the drive shaft 16. The value for the position of the drive shaft 16 is then formed from the signals of the virtual rotary encoder and auxiliary contact.
The control device 2, in particular the control unit 10 and/or the power section 11, is configured to control the motor 12 in an open-loop manner or in a closed-loop manner according to a feedback signal generated by the feedback system 4 on the basis of the value.
The control device 2, for example the control unit 10, uses the value for the position of the drive shaft 16 or actuating shaft 20 for position determination of the on-load tap changer 17. The control device 2, for example the control unit 10, controls the motor 12 in an open-loop and closed-loop manner so that it has a specified rotational speed according to the specifications.
When the on-load tap changer 17 is switched over or actuated, acceleration of the drive system 3, and in particular the motor 12, to a specified rotational speed, maintenance of this rotational speed thereby during the switchover and lowering of the rotational speed of the motor to 0 at the end of the switchover is continuously attempted. During the switchover or actuation of the on-load tap changer 17, the rotational speed of the motor 12 must not fall below a specified minimum value.
The actuating shaft 20 and the switching means (also referred to herein as a switch) 21 are mechanically connected or coupled to one another. The actuating shaft 20 may have cams which, from a certain point of the rotation of the actuating shaft 20, open and close, for example via a knee lever, the switching means 21, in particular vacuum interrupters. In this case, it is assumed that the energy required for actuating the switching means 21 is the same at all times. In other words, for actuating the switching means 21, a constant torque has to be applied at all times.
Since an ideal system is not involved, it is assumed that the motor 12 firstly makes the energy required for actuating the switching means 21 available in a delayed manner and the rotational speed of the motor 12 thus initially falls. The motor 12 then makes the energy available with a delay, whereby also the rotational speed increases.
Here, too, the first step 60 of the switchover is illustrated with delimitation. While the motor 12 of the drive system 3 is accelerating the actuating shaft 20, the kinetic energy in the whole mechanical system of the switch unit 1 increases.
Then, in the second step 70, the actuation of the switching means 21 occurs. Advantageously, in addition to the energy from the motor 12, use is made of the kinetic energy of the actuating shaft 20 to actuate the switching means 21. In other words, the momentum of the mass of the actuating shaft 20 assists the motor 12 during the actuation of the switching means 21. The actuating shaft 20 is used as a store for kinetic energy. It can see in the second step 60 that, when the switching means 21 is actuated, the rotational speed of the motor 12 briefly decreases and then increases again to the specified value.
Through the actuation of the switching means 21, in particular when the Geneva wheels of the switching means 21 are actuated, from a certain point, their inertia is abruptly coupled to the inertia of the actuating shaft 20. Shifting of kinetic energy from actuating shaft 20 into the switching means 21 occurs. Since the total energy remains unchanged, the rotational speed of the actuating shaft necessarily has to decrease. Since, then, the inertia of the actuating shaft 20 and that of the switching means 21 has to be accelerated, so that the motor attains the specified rotational speed, there is also an increase in the kinetic energy. When the switching means 21 is actuated, it is particularly important that the rotational speed does not fall below a certain minimum value 27. A fall below the minimum value could result in the switching means 21 being actuated too slowly. Switching times will then not be adhered to, so that electric arcs in the switching means 21 would not be able to be extinguished or transition resistors would be subjected to load for too long.
In
In this example, the inertia of the actuating shaft 20 is small. Therefore, it is necessary for a small torque to be applied to accelerate the actuating shaft 20. Only a small amount of kinetic energy is stored in the actuating shaft 20. Since this energy is significantly smaller than the work required for actuating the switching means 21, the rotational speed of the motor 12 falls considerably since the non-ideal drive system 3 requires a certain amount of time to introduce or refeed the lost energy back into the system. In other words, the energy removed from the system is very large in relation to the kinetic energy available prior to the actuation of the switching elements 21. In this case, the minimum value of the rotational speed 34 is fallen below, and this has an adverse effect on the switchover. In this respect, for example, switching times cannot be adhered to in the on-load tap changer 17.
The second pair of diagrams 40, 41 in
The third pair of diagrams 50, 51 in
In other words, the inertia of the actuating shaft 20 is selected to be of such a size that the torque 52 for accelerating and decelerating the actuating shaft 20, from the absolute value, is greater than or equal to the torque required by the switching means 21 during the switchover or actuation of the on-load tap changer 17.
Switchover is to be understood as meaning the actuation of the on-load tap changer. In this case, a switchover from one winding tap of a step transformer to an adjacent winding tap of the step transformer takes place.
While subject matter of the present disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. Any statement made herein characterizing the invention is also to be considered illustrative or exemplary and not restrictive as the invention is defined by the claims. It will be understood that changes and modifications may be made, by those of ordinary skill in the art, within the scope of the following claims, which may include any combination of features from different embodiments described above.
The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 116 421.4 | Jun 2021 | DE | national |
This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2022/065371, filed on Jun. 7, 2022, and claims benefit to German Patent Application No. DE 10 2021 116 421.4, filed on Jun. 25, 2021. The International Application was published in German on Dec. 29, 2022 as WO 2022/268489 A1 under PCT Article 21(2).
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/065371 | 6/7/2022 | WO |
