JPS6226270B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a control device for a polyphase induction motor capable of generating electric torque and braking torque.

By controlling the primary voltage applied to the polyphase induction motor to adjust the electric torque, and by generating braking torque by supplying DC power between the two phases of the polyphase induction motor, the polyphase induction motor can be controlled in the motor range. Continuous control is carried out from the start to the braking range. An example of such a control device is shown in FIG. In the figure, R, S, and T are bus bars of a three-phase AC power supply, 1 is a three-phase induction motor connected to a load (not shown), and 2 is a power control means connected between the three-phase AC power supply and the three-phase induction motor 1. It consists of thyristors 3, 4, 5, 6, 7, and 8 inserted in antiparallel to each bus bar. 9 is a speed detection means for extracting a speed signal according to the operating speed of the three-phase induction motor 1, and a speed generator 1 connected to the three-phase induction motor 1;
0. It is composed of a rectifier circuit 11 that rectifies the voltage generated by the speed generator 10. 12 is a speed command means for issuing a command signal corresponding to the operating speed in order to command the operating speed of the three-phase induction motor 1; 13 is amplifying the deviation value between the speed signal of the speed detection means 9 and the command signal of the speed command means 12; 14 is a second deviation detection means that inverts and amplifies the deviation signal of the first deviation detection means 13. The deviation signal outputted from the first deviation detection means 13 is positive in the range where the value of the command signal is greater than the value of the speed signal, and the deviation signal outputted from the second deviation detection means 14 is positive within the range where the value of the speed signal is greater than the value of the command signal. It is positive over a large range. 15
16 is a polarity detection means for detecting a range in which the value of the speed signal is larger than the command signal, 16 is a high-speed operation region detection means for detecting that the three-phase induction motor 1 is operating in a high-speed region close to the synchronous speed, and 17 is 3 This is a synchronization signal generating means that generates a synchronization signal every half cycle of the phase AC power supply. Reference numeral 18 denotes a thinning signal generating means, which inputs each signal from the polarity detecting means 15, the high-speed operation region detecting means 16, and the synchronous signal generating means 17, and inputs each signal from the polarity detecting means 15, the high-speed operation region detecting means 16, and the synchronous signal generating means 17, and inputs each signal from the polarity detecting means 15, the high-speed operation region detecting means 16, and the synchronous signal generating means 17, and determines whether the three-phase induction motor 1 is in a high-speed region close to the synchronous speed in the braking region. For example, a half-cycle output signal is generated every two cycles of a three-phase AC power source, and a half-cycle output signal is generated every cycle in other low-speed areas. Furthermore, when the three-phase induction motor 1 is in the motor range, the thinning signal generating means 18 takes in the synchronizing signal from the synchronizing signal generating means 17 and outputs a similar signal. Reference numerals 19 and 20 denote phase shifting means, which output the synchronization signal taken in from the synchronization signal generation means 17 as a timing signal according to the magnitude of the deviation signal taken in from the first deviation detection means 13 via diodes 21 and 22. Adjust ignition time. Also 23
is a synchronization signal generation means and a thinning signal generation means 1
The firing time for outputting the signal as a timing signal is adjusted according to the magnitude of the deviation signal taken in from the first and second deviation detection means 13 and 14 via the diodes 24 and 25. Reference numeral 26 denotes a drive means for emitting a drive signal for controlling the power control means 2, which captures and distributes the timing signals of the phase shift means 19, 20, 23, and controls the thyristors 3, 4, 5, 6, 7, 8. Thyristor drive circuits 27, 28, which issue ignition signals for ignition control;
Equipped with 29.

Next, the operation of the control device configured as described above will be explained. First, in the motor range where the value of the speed signal of the speed detection means 9 is smaller than the command signal of the speed command means 12, the deviation signal of the first deviation detection means 13 becomes a positive voltage, and the deviation signal of the first deviation detection means 13 becomes a positive voltage. , 20, 23. Further, the deviation signal of the second deviation detection means 14 becomes a negative voltage and is turned off by the diode 25. Further, since the output of the polarity detecting means 15 is at L level, the thinning signal generating means 18 outputs the synchronizing signal of the synchronizing signal generating means 17 to the phase shifting means 23 regardless of the signal of the high speed operation region detecting means 16. and transport means 19,2
By inputting the timing signals of 0 and 23 to the drive means 26, the power control means 2 is controlled and the operating speed of the three-phase induction motor 1 is adjusted. That is,
As the value of the deviation signal of the first deviation detection means 13 increases, each thyristor 3, 4, 5, 6, 7,
8 on-period increases. Therefore, the primary voltage applied to the three-phase induction motor 1 increases, and the electric torque of the three-phase induction motor 1 increases.

Next, when the value of the command signal from the speed command means 12 becomes smaller than the speed signal from the speed detection means 9 and the three-phase induction motor 1 enters the braking region, the first deviation detection means 1
The deviation signal of 3 becomes a negative voltage and the diodes 21, 2
2 and 24 are turned off. On the other hand, the deviation signal of the second deviation detection means 14 and the output signal of the polarity detection means 15 become positive voltages, and the diode 25 is turned on. Therefore, the phase shift means 23 adjusts the firing time from when the signal is taken in by the thinning control means 18 to when the timing signal is issued, depending on the magnitude of the deviation signal. That is, in the low-speed operation region of the three-phase induction motor 1 where the output signal of the high-speed operation region detection means 16 is at L level, the thinning control means 18
The timing signal of the phase shift means 23 is applied to the drive means 26 by the output signal which is emitted only for half a cycle in one cycle of the phase AC power supply, and the power control means 2
supplies DC current between two phases, for example, between the R phase and the T phase, and power generation (DC) braking of the three-phase induction motor 1 is performed. In addition, in the high-speed operation region of the three-phase induction motor 1 where the output signal of the high-speed operation region detection means 16 is at H level, the thinning control means 18
The timing signal of the phase shift means 23 is applied to the drive means 26 by the output signal which is emitted only during two and a half cycles of the phase AC power supply, and the power control means 2
A DC current is supplied between two phases, for example, between the R phase and the T phase, and power generation (DC) braking of the three-phase induction motor 1 is performed. This will be further explained with reference to FIG. In Fig. 2, the horizontal axis is the operating speed N of the three-phase induction motor 1, and the vertical axis is the torque 7 generated in the three-phase induction motor 1.
The positive range represents electric torque, and the negative range represents braking torque. In other words, in the figure, A is the electric torque characteristic when each thyristor 3, 4, 5, 6, 7, and 8 is conductive, and B is the electric torque characteristic when either thyristor 3, 8 or thyristor 4, 7 is connected to one cycle of the three-phase AC power supply. This is the braking torque characteristic when it is conductive for half a cycle, and electric torque is generated in the high-speed operation region near the synchronous speed No. In addition, C is the braking torque characteristic when either thyristors 3 and 8 or thyristors 4 and 7 are conducted for half a cycle in two cycles of a three-phase AC power supply, and in the high-speed operation region near the synchronous speed No. Sufficient braking torque is generated. Therefore, the high-speed operation area detection means 16 detects the high-speed operation area and determines the speed.
By switching between the two braking states at _N1 , braking torque can always be obtained in the braking range of the three-phase induction motor 1, as shown by the solid line D in the diagram.

Now, in such a control device, a digital circuit that handles various pulse signals and an analog circuit that amplifies the amount of deviation between the two signals are not mixed together. Therefore, noise enters the digital circuit side from the analog circuit side, and the digital circuit side is likely to malfunction. Therefore, when the three-phase induction motor 1 is operating in the electric range, for example, if the digital circuits of the polarity detection means 15, the high-speed operation region detection means 16, or the thinning signal generation means 18 receive noise from the analog circuit and malfunction, the phase shift means 23 In this case, a signal similar to the synchronization signal of the synchronization signal generation means 17 is not inputted from the thinning signal generation means 18. For this reason, the phase shift means 23 outputs an ignition signal at different timings, and the speed of the three-phase induction motor cannot be adjusted normally.

Therefore, the present invention provides a highly reliable control device for a multiphase induction motor that can perform normal speed control even if the digital circuit malfunctions due to noise or the like, particularly in the motorized range.

The embodiment shown in FIG. 3 will be described below. Components designated by the same reference numerals as the control device shown in FIG. 1 have the same function, and therefore their explanation will be omitted. Reference numeral 30 denotes a phase shift means, which includes diodes 24 and 25 as shown in the figure.
The ignition time for outputting the synchronizing signal taken in from the synchronizing signal generating means 17 as a timing signal is adjusted according to the magnitude of the deviation signal of the first and second deviation detecting means 13 and 14 inputted through the synchronizing signal generating means 17, respectively. 3
Reference numeral 1 denotes a thinning control means which receives the voltage of one phase of the three-phase AC power source and the output signal of the high-speed operation region detection means 16, and detects a second deviation applied to the phase shifting means 30 in the braking region of the three-phase induction motor 1. The deviation signal of the means 14 is controlled. 37 is a diode as a unidirectional element, which allows only the signal from the second deviation detection means 14 to the thinning control means 31 to pass through. FIG. 4 shows the configuration of the thinning control means 31. In other words, the circuit before the JK flip-flop 32 is a waveform shaping circuit that shapes a sine waveform taken in between the R-phase and T-phase lines of a three-phase AC power supply and obtains a pulse signal at a rate of one per cycle.
The flip-flop 33 is a circuit for obtaining a pulse signal once every two cycles of the three-phase AC power supply.
NAND circuit 34 and OR circuit (NOT circuit + OR
A circuit) 35 is a JK flip-flop 33 when the output of the high-speed operation region detection means 16 is at H level.
This is a signal selection circuit for taking out the output of the JK flip-flop 32 when the output of the high-speed operation region detection means 16 is at L level. The transistor 36 and the diode 37 are a cancel circuit that functions to prevent the deviation signal from the second deviation detection means 14 from being input to the phase shifting means 30 when the output of the signal selection circuit is at H level.

Next, the operation in the electric range of the three-phase induction motor 1 of the control device configured as described above will be explained based on FIG. 3. In the electric range, the deviation signal of the first deviation means 13 becomes a positive voltage, and the diodes 21, 22, 2
4 to the phase shift means 19, 20, 30. These phase shifting means 19, 20, and 30 each receive a synchronizing signal from the synchronizing signal generating means 17, and output a timing signal corresponding to the deviation signal of the first deviation means 13 to the driving means 26. The drive means 26 controls the power control means 2 and controls the three-phase induction motor 1.
operating speed is adjusted. Here, since the second deviation detection means 14 inverts and amplifies the deviation signal of the first deviation detection means 13, the deviation signal in the electric range becomes a negative voltage. Therefore, even if the thinning control means 31 malfunctions due to noise or the like, the deviation signal of the second deviation detection means 14 is turned off by the diode 37. Therefore, the phase shifting means 19, 20, and 30 are not affected by the malfunction of the thinning control means 31 and are always normally controlled.

Next, the operation of the three-phase induction motor 1 of the control device in the braking range will be explained with reference to FIG. In FIG. 5, the horizontal axis shows the passage of time t, and the vertical axis shows the waveform of the output signal of each circuit indicated by the numerals. In other words, the transistor 3
6 repeats on and off, the deviation signal of the second deviation detection means 14 is periodically canceled, and the phase shift means 30 receives one or two cycles of the power frequency.
The deviation signal is transmitted for a period of half a cycle. In other words, while the output of the high-speed operation region detection means 16 is at the L level, the deviation signal remains at the phase shift means 3 for a period of half a cycle for every cycle of the power supply frequency.
0, and DC power is supplied to the winding connected between the R phase and the T phase of the three-phase induction motor 1. Further, when the output of the high-speed operation region detection means 16 becomes H level, a deviation signal is applied to the phase shift means 30 for a period of half a cycle to two cycles of the power supply frequency, and the deviation signal is applied to the three-phase induction motor 1 at 1/2 of the power supply frequency. DC power is supplied only during the thinned out half cycles. In this way, when DC power is supplied between the two phases of the three-phase induction motor 1, the three-phase induction motor 1 always generates braking torque during the operation period, as already explained with reference to FIG.

In the above embodiment, a JK flip-flop was used to shape the power waveform, but this
As shown in FIG. 6, two inverter gates may be combined, or a Schmitt circuit may be used. Furthermore, in the embodiment described above, the period during which DC power is supplied in two stages in the braking region is adjusted;
By adjusting the period during which the deviation signal of the deviation detection means is canceled, it is possible to switch to a larger number of stages. Furthermore, the deviation signal of the second deviation detection means was obtained by inverting the deviation signal of the first deviation detection means 13;
It can also be directly determined from the difference signal between the speed signal of 1 and the command signal of the speed command means 12.

As is clear from the above description, in the control device according to the present invention, the phase shift means for outputting a timing signal to the drive means for controlling the power control means inputs the synchronization signal of the synchronization signal generation means, and the thinning control means and the Since a unidirectional element is provided between the second deviation detecting means and the second deviation detecting means, even if the thinning control means made of a digital circuit malfunctions due to noise, the phase shift means will not malfunction in the motorized range. In other words, in the motor range of the polyphase induction motor that is most commonly used, the synchronization signal from the synchronization signal generation means is reliably supplied to the phase shift means, thereby preventing accidents such as when the polyphase induction motor becomes uncontrollable. I can do it. Therefore, this has the effect of increasing the reliability of the control device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining the configuration of a conventional control device for a polyphase induction motor, FIG. 2 is a diagram for explaining the torque generated by the control device shown in FIG. 1, and FIG. A block diagram for explaining one embodiment of the invention, FIG. 4 is a diagram for explaining the configuration of the thinning control means shown in FIG. 3, and FIG. 5 is a diagram for explaining the embodiment shown in FIGS. 3 and 4. FIG. 6 is a timing diagram for explaining the operation of FIG. 6, and is a diagram for explaining another embodiment of the waveform shaping circuit of the thinning control means explained in FIG. 1... polyphase induction motor, 2... power control means,
9...Speed detection means, 12...Speed command means, 1
3...First deviation detection means, 14...Second deviation detection means, 16...High speed operation region detection means, 17
... Synchronization signal generation means, 19, 20, 30 ... Phase shifting means, 26 ... Driving means, 31 ... Thinning control means, 37 ... Diode as a unidirectional element.

Claims (1)

[Claims] 1. In a control device that performs primary voltage control of the polyphase induction motor in the motor range of the polyphase induction motor and supplies DC power between two phases in the braking range, a speed detection means for detecting the operating speed of the polyphase induction motor; ,
A speed command means for commanding the operating speed of the polyphase induction motor; and a first deviation detection means for comparing the signals of the speed detection means and the speed command means and detecting a deviation between the two signals in the motor range of the polyphase induction motor. and a second device for comparing the signals of the speed detection means and the speed command means and detecting a deviation between the two signals in the braking region of the polyphase induction motor.
a deviation detection means for detecting deviation of the polyphase induction motor; a synchronization signal generation means for generating an output every half cycle of a polyphase power supply connecting the polyphase induction motor;
phase shifting means for controlling the phase of the output signal according to the magnitude of the signal from the deviation detection means; and power control means for receiving the signal from the phase shifting means and connected between the polyphase induction motor and the polyphase power source. a drive means for controlling; a high-speed operation range detection means for detecting a high-speed operation range of the polyphase induction motor; and a high-speed operation range detection means for detecting the second deviation for each cycle exceeding one cycle of the polyphase power supply in response to a signal from the high-speed operation range detection means. a decimation control means for transmitting a signal from the detection means to the phase shift means; connected between the decimation control means and the second deviation detection means;
A control device for a polyphase induction motor, comprising: a unidirectional element that passes a signal from the second deviation detection means to the thinning control means.