METHOD AND APPARATUS FOR SPEED CONTROL SELECTION IN ELECTRONICALLY COMMUTATED MOTOR

Abstract

This invention relates to a method of speed control selection for an electronically commutated motor comprising the following steps: (a) a motor controller receives an input signal T from a speed control selection circuit; (b) the motor controller retrieves a corresponding value for a motor running speed S from a comparison list correlating the input signal with the motor running speed, which list has been stored in the motor controller in advance, by searching the comparison list for the input signal T; and (c) the motor controller controlling a motor M to run at the motor running speed S, achieving the purpose of the speed selection. This method allows for from 2 to 256 speed choices with a single signal wire only. Such a circuit structure has the advantages of high integration, simple wiring, low cost, good performances, low failure rate, higher number of optional speeds, and simpler and more practical control.

Description

BRIEF DISCRIPTION OF THE DRAWINGS

The preferred embodiments of the invention will hereinafter be described in more detail with reference to the accompanying drawings, in which:

FIG. 1 is a schematic block diagram showing a traditional method for speed control selection of an electronically commutated motor (prior art);

FIG. 2 is a schematic block diagram showing one embodiment of the invention;

FIG. 3 illustrates voltage input signal as a function of time according to an embodiment of the invention;

FIG. 4 illustrates pulse input signal as a function of time according to an embodiment of the invention;

FIG. 5 illustrates frequency input signal as a function of time according to an embodiment the invention;

FIG. 6 is a flowchart showing speed selection steps according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 6, the speed control selection method for an electronically commutated motor comprises the steps of:

(a) a motor controller receiving an input signal from a speed control selection circuit;

(b) the motor controller retrieving a value for the motor running speed S from a comparison list correlating the input signal with the motor running speed, which list has been stored in the motor controller in advance, by searching the comparison list for the input signal T; and

(c) the motor controller controlling a motor M to run at the speed S.

In the above step (c), the motor controller controls the running speed of the motor via controlling the average operating voltage or the average running current of the motor.

In the above step (a), the input signal can be a voltage signal. This voltage signal is variable over a certain range, so that the motor controller can find the related motor running speed S in the above mentioned comparison list, based on the value of the input voltage. An example of a comparison list applicable to a voltage signal is shown in Table 1.

TABLE 1
Input signal
voltage T (V) Speed S (rpm)
10            300
9.5           400
9             500
8.5           600
8             700
7.5           800
7             900
6.5           1000
6             1100
5.5           1200
5             1300
4.5           1400
4             1500
3.5           1600
3             1700
2.5           1800
2             2000

In the above step (a), alternatively, the input signal is a pulse signal with a certain duty cycle. The duty cycle of the pulse signal, as used herein, refers to the product of the pulse duration and pulse repetition frequency of a pulse carrier, equal to the time per second that pulse power is applied, usually expressed as percentage. Duty cycle is also known as duty ratio or duty factor. The duty cycle of the pulse signal is variable over a certain range, so that the motor controller can find the related motor running speed S in the above-mentioned comparison list, based on the value of the duty cycle of the pulse signal. An example of a comparison list applicable to a pulse signal with certain duty cycle is shown in Table 2.

TABLE 2
Pulse signal duty
cycle (%) Speed S (rpm)
5         300
8         400
12        500
15        600
18        700
22        800
25        900
28        1000
32        1100
35        1200
38        1300
44        1400
47        1500
50        1600
52        1700
55        1800
60        2000

In the above step (a), the input signal is a frequency signal, e.g., a sine wave or square wave with a certain frequency. The frequency of this sine wave or square wave is variable over a certain range, so that the motor controller can find the related motor running speed S in the above mentioned comparison list, based on the value of the input frequency of the sine wave or square wave. An example of a comparison list applicable to a frequency signal is shown in Table 3.

TABLE 3
Frequency (Hz) Speed S (rpm)
100            300
200            400
300            500
400            600
500            700
600            800
700            900
800            1000
900            1100
1000           1200
1100           1300
1200           1400
1300           1500
1400           1600
1500           1700
1600           1800
1700           2000

Although correlation tables shown above (Tables 1-3) list 17 optional speeds each, they are shown for illustrative purposes only. It is to be understood that a much greater number, for example, 50, or 100, or 150, or 256 or more, optional speeds can be transferred from a speed selection control circuit to a motor controller using one wire only. For example, to select 256 optional speeds, e.g., motor speeds from 110 rpm up to 2660 rpm evenly spaced by 10 rpm apart (110 rpm, 120 rpm, 130 rpm, . . . , 2660 rpm) using voltage signal, the voltage signal assumes 256 different values from 26.6 V down to 1.1 V evenly spaced by 0.1 V apart (26.6 V, 26.5 V, 26.4 V . . . 1.1 V). Similarly, for example, to select 256 optional speeds, e.g., from 110 up to 2660 rpm evenly spaced by 10 rpm apart (110 rpm, 120 rpm, 130 rpm, . . . , 2660 rpm) by using pulse signal having a certain duty ratio, the duty ratio assumes 256 different values from 1.1% up to 52.1% spaced evenly at 0.2% apart (1.1%, 1.3%, 1.5% . . . 52.1%). Similarly, for example, to select 256 optional speeds, e.g., from 110 rpm up to 2660 rpm evenly spaced by 10 rpm apart (110 rpm, 120 rpm, 130 rpm, . . . , 2660 rpm) using frequency signal, the frequency of the signal assumes 256 different values from 100 Hz up to 5.1 kHz spaced evenly by 20 Hz apart (100 Hz, 120 Hz, 140 Hz . . . 5100 Hz).

As shown in FIG. 2, the speed control selection apparatus for an electronically commutated motor, which apparatus carries out speed control selection, comprises a motor controller and a speed control selection circuit. The output end of the motor controller is connected to the motor; the output end of the speed selection circuit is connected to the input end of the motor controller. The speed selection circuit is either connected to the motor controller directly or via a photoelectric coupled circuit, so that the motor controller is isolated from the speed selection circuit. The speed selection circuit is a voltage generating circuit having a variable voltage output (for example: a voltage regulator). Alternatively, it is a pulse generating circuit having variable pulse duty cycle output (for example: a PWM pulse width modulator). Alternatively, it is a sine wave or square wave generating circuit with a variable frequency output.

As shown in FIG. 3 and Table 1, if the input signal is a voltage signal, the various speeds are selected by adjusting the input voltage value. As shown in FIG. 4 and Table 2, if the input signal is a pulse signal having a certain duty cycle, the various speeds are selected by adjusting the input pulse duty cycle value. As shown in FIG. 5 and Table 3, if the input signal is a frequency signal, the various speeds are selected by adjusting the frequency value.

This invention is not to be limited to the specific embodiments disclosed herein and modifications for various applications and other embodiments are intended to be included within the scope of the appended claims. While this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification, and following claims.

All publications and patent applications mentioned in this specification are indicative of the level of skill of those skilled in the art to which this invention pertains. All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application mentioned in this specification was specifically and individually indicated to be incorporated by reference.

Claims

1. A method of speed control selection for an electronically commutated motor, comprising the steps of: (a) a motor controller receiving an input signal T from a speed control selection circuit;(b) said motor controller retrieving a corresponding value for a motor running speed S from a comparison list correlating said input signal with the motor running speed, which list has been stored in the motor controller in advance, by searching said comparison list for said input signal T; and(c) said motor controller controlling a motor M to run at said motor running speed S.

2. The method of claim 1, wherein said motor controller controls the motor M to run at said running speed S with a closed loop control mode, allowing the running speed to fluctuate within a small range, and keeping the motor at a stable speed.

3. The method of claim 1, wherein said input signal T is a voltage signal, said voltage signal having a certain voltage, said voltage being variable over a certain voltage range so as to allow the motor controller to retrieve the corresponding value for said motor running speed S based on the input voltage value from the comparison list correlating the input signal with the motor running speed.

4. The method of claim 2, wherein said input signal T is a voltage signal, said voltage signal having a certain voltage, said voltage being variable over a certain voltage range so as to allow the motor controller to retrieve the corresponding value for said motor running speed S based on the input voltage value from the comparison list correlating the input signal with the motor running speed.

5. The method of claim 1, wherein said input signal T is a pulse signal, said pulse signal having a pulse width duty cycle, said duty cycle being variable over a certain duty cycle range so as to allow the motor controller to retrieve the corresponding value for said motor running speed S based on the duty cycle from the comparison list correlating the input signal with the motor running speed.

6. The method of claim 2, wherein said input signal T is a pulse signal, said pulse signal having a pulse width duty cycle, said duty cycle being variable over a certain duty cycle range so as to allow the motor controller to retrieve the corresponding value for said motor running speed S based on the duty cycle from the comparison list correlating the input signal with the motor running speed.

7. The method of claim 1, wherein said input signal T is a frequency signal, said frequency signal having a certain frequency, said frequency being variable over a certain frequency range so as to allow the motor controller to retrieve the corresponding value for said motor running speed S based on the frequency from the comparison list correlating the input signal with the motor running speed.

8. The method of claim 2, wherein said input signal T is a frequency signal, said frequency signal having a certain frequency, said frequency being variable over a certain frequency range so as to allow the motor controller to retrieve the corresponding value for said motor running speed S based on the frequency from the comparison list correlating the input signal with the motor running speed.

9. The method of claim 7, wherein said frequency signal is a sine wave or square wave.

10. The method of claim 8, wherein said frequency signal is a sine wave or square wave.

11. A speed control selection apparatus for an electronically commutated motor comprising: a motor controller having an input terminal; anda speed control selection circuit having an output terminal; whereinsaid motor controller is electrically connected to the electronically commutated motor;said output terminal of said speed control selection circuit is (i) directly electrically connected to said input terminal of said motor controller, or (ii) connected to said input terminal of said motor controller via a photoelectric coupled circuit, said photoelectric coupled circuit isolating said motor controller from said speed control selection circuit;said speed control selection circuit transmits an input signal T to said motor controller via one wire only;said motor controller carries out the following steps: (i) retrieving a corresponding value for a motor running speed S from a comparison list correlating said input signal with the motor running speed, which list has been stored in the motor controller in advance, by searching said comparison list for said input signal T; and (ii) controlling a motor M to run at said motor running speed S.

12. The speed control selection apparatus of claim 11, wherein said speed control selection circuit is: a voltage generating circuit having a variable voltage output;a pulse generating circuit having a variable duty cycle output; or a sine wave or square wave generating circuit with a variable frequency output.