JPH039715B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a converter device for driving an induction motor, which is used as a servo motor to eliminate the deviation between a detected value of a controlled object and a target setting value.
Specifically, the present invention relates to a converter device for driving an induction motor used for speed control or positioning control of a mechanical continuously variable transmission.

To control the speed of an induction motor, the drive frequency may be made variable. Normally, to make the frequency variable, there is an inverter device that converts the commercial power supply voltage into DC voltage, and then converts that DC voltage into AC voltage of an arbitrary frequency. There is a converter device that attempts to obtain an AC voltage of any frequency by controlling the phase of the AC voltage using a thyristor.

Since the latter does not require a structure for converting direct current, it has the advantage of being simpler in structure than the former. The present invention relates to the latter, that is, to converter devices.

By the way, when controlling the frequency of an induction motor, it is necessary to increase the voltage as the driving frequency of the induction motor increases. A conventional converter device is composed of a voltage generation circuit, a frequency generation circuit, etc., and the frequency generation circuit includes, for example, a V/F.
I was using a converter. However, for a converter device with a simple configuration, a V/F converter is expensive.

It is also possible to control the induction motor at a frequency that is synchronized with the power supply voltage, but if you try to obtain this frequency using a frequency divider circuit, the frequency division ratio is an integer, so the divided frequency is not continuous, so continuous speed control cannot be expected.

As a converter device used for speed control of an induction motor, this invention continuously increases the drive frequency as the input voltage continuously increases, using a simple configuration without using an expensive V/F converter. An object of the present invention is to provide a converter device for an induction motor that can perform the following steps.

An embodiment of the invention will be explained with reference to FIG.
Note that Figure 2 is a time chart. 1 is an input terminal, and 2 is an induction motor. 8 is the controlled object,
For example, a mechanical continuously variable transmission. The induction motor 2 is used to change the gear ratio of the continuously variable transmission 8.

The deviation between the detected value (for example, voltage) corresponding to the controlled quantity (for example, rotation speed) detected from the controlled object 8 via the detector 9 and the target setting value is given to the input terminal 1 as a deviation input b. .

3 is a phase control circuit, which receives commercial power supply voltage a from power supply terminal 4, and outputs a phase control signal c that is synchronized with this voltage a and has a width that is in a constant relationship (proportional relationship or functional relationship) with deviation input b. be done.

More specifically, the phase control signal c is designed to fall when the voltage a is zero or near zero, and the pulse width becomes larger as the deviation input b becomes larger.

The phase control signal c is applied to a pulse generation circuit 5, which outputs a pulse d of a constant frequency only during the period when the signal c is valid. The pulse d is given to a frequency dividing circuit 6, where it is divided into pulses e ₁ , e with a phase difference approximately corresponding to the number of phases of the induction motor 2 (approximately 90 degrees in the case of two phases, approximately 120 degrees in the case of three phases). ₂ (The example in the figure is a two-phase induction motor, so the output is two-phase pulses.)

Note that if the frequency of the pulse d, which is output only when the phase control signal c is present, is divided in this way, even if the phase difference is greater than the phase difference corresponding to the number of phases during the period when the phase control signal c is not present, the induction motor can be When used as a servo motor, there is little effect on the rotation speed.

These pulses e ₁ and e ₂ are applied to the drive circuit 7.
The drive circuit 7 also receives the above-mentioned phase control signal c and power supply voltage a as inputs. The thyristor supplies a power supply voltage a to the stator winding of the induction motor 2, and is comprised of a thyristor that controls the phase and a circuit that generates a gate pulse that controls the conduction angle of the thyristor. Output f ₁ , f ₂
indicates the voltage applied to each stator winding.

This drive circuit 7 conducts the positive half-wave of _the power supply voltage a through the thyristor only during the valid period of the phase control signal c during the valid period of the pulses e _{1 and e 2 .}
The thyristor is configured to conduct the negative half-wave of the power supply voltage a only during the valid period of the phase control signal c while _e2 is invalid.

In the above configuration, a case where the deviation input b is small will be described. In this case, the width of the phase control signal c is narrow. Since the frequency of the pulses d during the valid period of the phase control signal c is constant, the number of pulses d during the valid period of one phase control signal c is therefore small, and therefore the output pulse of the frequency dividing circuit 6
The periods of e ₁ and e ₂ become longer.

Since the period of pulses e ₁ and e ₂ determines the generation period of positive and negative voltages of outputs f ₁ and f ₂ ,
Therefore, the frequency determined by the period during which the positive and negative voltages of the outputs f ₁ and f ₂ are generated, that is, the converter frequency, becomes lower as shown by the dotted line in the figure. This causes the induction motor 2 to rotate at a low speed.

Note that the pulses e ₁ and e ₂ in this case are asynchronous with respect to the power supply voltage a, and therefore can be continuously changed to any width without being restricted by the power supply frequency. Therefore, the rotational speed of the induction motor 2 can be changed continuously.

On the other hand, as the deviation input b becomes smaller, the width of the phase control signal c becomes narrower, but for this reason, the outputs f ₁ , f ₂
The output width of one of them also becomes narrower. Therefore the output
The average voltage during the half cycle of f ₁ and f ₂ decreases.
In other words, the input voltage of the induction motor becomes smaller.

Conversely, when the deviation input b is large, the width of the phase control signal c becomes wide, the input voltage becomes high, and the driving frequency also becomes high.

As mentioned above, when the deviation input b is large, the induction motor 2 rotates at high speed, and when the deviation input b is small, it is driven at low speed, and the detected value of the controlled object and the target setting value are It continues to be driven until the deviation of becomes zero.

FIG. 3 shows another embodiment of the invention, and FIG. 4 shows a time chart. Note that FIG. 3 also shows a detailed example of the phase control circuit 3. This configuration attempts to reverse or reverse the induction motor 2 according to the polarity of the deviation input b. The polarity of the deviation input b is determined by the polarity discrimination circuit 11, and for example, an output that becomes effective when the polarity is positive. h and feeds it to the drive circuit 7.

When the drive circuit 7 receives the output h, the outputs e ₁ , e ₂
Reverse the polarity of either one. FIG. 4 shows an example in which the output e ₂ is inverted. As a result, the phase of the output f ₂ is reversed with respect to f ₁ , and the induction motor rotates in the opposite direction to the direction of rotation when the output h is invalid.

The deviation input b is also given to the insulation value circuit 12,
The absolute value of deviation input b is defined as deviation input b'. The phase control circuit 3 is composed of an integrating circuit 13, a comparator circuit 14, and a reset circuit 15.

The reset circuit 15 outputs a signal a' synchronized with the power supply voltage a at or near zero, and supplies it to the integrating circuit 13 as a reset signal. The integrating circuit 13 repeatedly integrates the deviation input b' until it is reset by the signal a', and outputs an output g.

The output g is compared with the reference voltage _E1 at the power supply terminal 14, and an output c is produced which is valid only during the period when the output g is greater than the voltage _E1 . This output c is nothing but the phase control signal c mentioned above. The subsequent operations are no different from those shown in FIG.

FIG. 5 shows a circuit diagram showing the relationship between the drive circuit 7 of FIG. 3 and the induction motor 2. FIG. 6 is a time chart of FIG. 5. In Figure 5, 21-2
3 is an exclusive OR circuit; 24 and 25 are AND circuits; 26 is a comparator circuit that outputs a signal c that is invalid during the positive half-wave period of the power supply voltage a; 27 and 28 are bidirectional three-terminal thyristors; 29 and 30 are stator windings of the induction motor 2.

When the output h is valid, during the period of the negative waveform of the power supply voltage a when the output e ₂ is valid, and during the period of the positive waveform when the output e ₂ is invalid,
The thyristor is made conductive during the effective period of each pulse c.

Similarly, when output h is invalid, during the period of the positive waveform of power supply voltage a when output e ₂ is valid,
Further, when the output e ₂ is invalid, the thyristor is made conductive during the valid period of the pulse c during the period of the negative waveform.

As detailed above, according to the present invention, the input voltage applied to the induction motor can be controlled with a simple configuration by using a phase control signal that is synchronized with the commercial power supply and whose pulse width has a fixed relationship with the deviation voltage. Since it is possible to continuously change the frequency and change the input voltage continuously, speed control and positioning control of mechanical continuously variable transmissions can be performed with a simple configuration. It has a certain effect.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a time chart for explaining the operation, and Fig. 3 is a block diagram showing an embodiment of the present invention.
The figure is a block diagram showing another embodiment of the present invention.
FIG. 4 is a time chart for explaining the operation, FIG. 5 is a circuit diagram showing an example of a drive circuit, and FIG. 6 is a time chart for explaining the operation. 1... Deviation voltage input terminal, 2... Induction motor,
3... Phase control circuit, 4... Drive power input terminal,
5... Pulse generation circuit, 6... Frequency dividing circuit, 7...
drive circuit.

Claims (1)

[Scope of Claims] 1. Deviation between a target setting value and a detected value corresponding to a controlled variable detected from a controlled object that is synchronized with the voltage of a power source for driving an induction motor and is driven by the induction motor. a phase control circuit that generates a phase control signal with a pulse width that has a constant relationship with an input; a pulse generation circuit that generates a fixed-period pulse during a valid period of the phase control signal; a frequency divider circuit that outputs a multi-phase output having a phase difference approximately corresponding to the number of phases; the multi-phase output and the phase control signal are input, and the induction motor A converter device for driving an induction motor, comprising a drive circuit that controls the drive frequency of the drive circuit and the voltage of the drive power source so as to change the input voltage of the induction motor in accordance with the phase control signal.