JPS59230483A - Speed monitoring system of synchronous motor - Google Patents

Abstract

PURPOSE:To enable to monitor the speed even when the speed signal from a tachometer generator is interrupted by monitoring the rotating speed by the logic sum of the output of a pulse width modulator and an interphase energizing timing signal obtained from a phase current signal. CONSTITUTION:A DC/3-phase converter 19 outputs 3-phase AC signals IU-IW by a deviation IS between a speed command voltage VCMD and the actual speed voltage TSA from a tachometer generator 16 and a signal from a pulse coder 15. A pulse width modulator 26 outputs pulse width modulation signals S1-S6 to an inverter 13 in response to a deviation between the signals IU-IW and a phase current. An interphase energizing timing circuit 27 outputs an interphase energizing timing signal by the signals S1-S6 and the phase current, and the timing signal becomes a rotating speed signal through an OR gate 28 and a filter 29.

Description

TECHNICAL FIELD The present invention relates to a speed monitoring system for a synchronous motor driven by a pulse width modulation system.

Conventional technology A drive device that controls the speed of a synchronous motor using alternating current generally uses a pulse width modulation circuit that pulse-width-modulates a sine-wave current command to drive an inverter circuit and provides a pulse-width-modulated sine wave to the synchronous motor. It is being In the case of three-phase AC drive, this inverter circuit uses a total of six transistors, two for each phase, and the two transistors for each phase are controlled so that their on/off operations are reversed.

The difference between the speed command signal and the output of the tachogenerator directly connected to the synchronous motor is determined, and the difference signal is applied to a DC/3-phase conversion circuit via an amplifier, where it is converted to 3-phase AC and output for each phase. The difference between the current of each phase of the armature of the synchronous motor is determined. The current command signal from which the difference has been determined is supplied to the Nords width modulation circuit via an amplifier.

In the above-mentioned synchronous motor drive system, when monitoring the speed of the synchronous motor, the speed feedback signal from the tacho generator is used or the signal from the noise coder is used. There is a problem in that when the supply couple is broken, etc., it is impossible to obtain a signal and it is not possible to issue an alarm in case of an emergency.

OBJECTS OF THE INVENTION In view of the problems with the conventional devices described above, the object of the present invention is based on the concept of using a logic circuit of a signal obtained by performing a logical operation on the output signal of a pulse width modulation circuit by a phase-to-phase energization timing circuit. To enable monitoring of the speed of a synchronous motor even if a speed signal from a tachogenerator or pulse coder is cut off.

Structure of the Invention In the present invention, a speed signal adder receiving a speed command;
A DC/3-phase conversion circuit that receives the output of the speed signal adder and converts it from DC to 3-phase AC, 3 current signal adders each receiving the three outputs of the DC/3-phase conversion circuit, and the current A pulse width modulation circuit that receives three outputs from the signal adder and outputs a pulse width modulated signal, an inverter circuit that receives the output of the pulse width modulation circuit, and a synchronous motor driven by the output of the inverter circuit. and a pulse coder and a tacho generator connected to the synchronous motor, the output of the tacho generator being subtractedly added to the speed signal adder, and the output of the pulse coder being subtracted from the speed signal adder.
In a speed monitoring system for a driving device for a synchronous motor, the pulse is supplied to a three-phase conversion circuit, and a signal corresponding to a current value of each phase of the synchronous motor is supplied so as to be subtracted by the current signal adder. Receiving the output of the width modulation circuit and the phase current signal of the synchronous motor receives six output signals from the phase-to-phase energization timing circuit and the phase-to-phase energization timing circuit for obtaining the phase-to-phase energization timing signal of the synchronous motor, and calculates the logical sum thereof. A speed monitoring method for a synchronous motor is provided, which includes an OR circuit and a filter circuit that smoothes the output rectified by the OR circuit, and monitors the rotation speed based on the output of the filter circuit.

Embodiment A block circuit diagram of a drive device using a speed monitoring system for a synchronous motor as an embodiment of the present invention is shown in the drawings. 3
The alternating current from the phase alternating current power supply 11 is rectified and smoothed by a rectifier circuit 12 and then supplied to an inverter circuit 13 . The output of the inverter circuit 13 is supplied to the synchronous motor 14 via current transformers 30, 31, and 32t. A pulse coder 15 and a tacho generator 16 are connected to the synchronous motor 14 . On the other hand, the speed command voltage VCMD from the speed command circuit and the synchronous motor 1 from the tacho generator 16 are not shown.
The difference between the actual speed voltages TSA proportional to the rotational speed of 4, that is, the speed error ER, is determined by the speed signal adder 17, and is amplified by the error amplifier 18 to become the signal Is.
It is added to the DC/three-phase conversion circuit 19. In the DC/three-phase conversion circuit 19, three-phase AC signals Iu, Iv, and Iw are generated by the signal Is and the signal from the pulse coder 15.
is made. That is, since the pulse coder 15 is capable of absolute position detection and information on the armature position g can be obtained, a sine wave voltage and a cosine wave voltage corresponding to the position of the field pole of the synchronous motor 14 can be obtained. A two-phase signal is obtained by multiplying by the sine wave voltage and cosine wave voltage, and the two-phase signal is further converted into three-phase current commands Iu, Iv using an operational amplifier (not shown).
and convert to Iw. This Iu, Iv and Iw
have a phase difference of 2" from each other, and the synchronous motor 14
This is a three-phase current command that is in phase with the induced electromotive force.

Three-phase current commands Iu, Iv and Iw are applied to current signal adders 20, 21 and 22, respectively, and current transformer 3
The difference with the actual phase current from 0.31 and 32 is determined, respectively. Note that the output of one current transformer can be calculated from the output of the other two current transformers, so normally two current transformers are used, but for convenience of explanation, three current transformers are used here. It is listed as having been.

The outputs of adders 20.21 and 22 are sent to current amplifiers 23.
The signals are amplified at 24 and 25 and supplied to a pulse width modulation circuit 26. In the pulse width modulation circuit 26, the triangular wave signal and the
Comparing the amplitudes of the phase alternating current signals, inputting a pulse width modulated three-phase current command to the base of each power transistor Q1 to Q6 constituting the inverter circuit 13, controlling the power transistors Q1 to Q6 on and off, Three-phase current is supplied to the synchronous motor 14.

The output signals S1 to 86 of the pulse width modulation circuit 26 (connected to the paces of transistors Q1 to LQ6, respectively) are further connected to an interphase current timing circuit 27.

In addition, the interphase energization timing circuit 27 includes a current transformer 30.
Signals from 31 and 32 are provided to provide information as to whether the phase current is in a power supply or regeneration state. In response to the input signal described above, the phase-to-phase energization timing circuit 27 uses a logic circuit provided in the circuit to generate a timing signal (square wave signal) for current to flow from transistor Q1 to Q4, to transistor Q1 to Q6, and to transistor Q3.
Timing signals are output as six outputs, causing current to flow from transistor Q2 to transistor Q2, from transistor Q3 to Q6, from transistor Q5 to Q2, and from transistor Q5 to Q4, respectively.

The logical sum of these six outputs is determined by the OR gate 28, and the rectified logical sum signal is smoothed through the filter 29 to obtain a DC signal. Since this DC signal corresponds to the voltage component applied to the motor, the voltage value corresponds to the rotational speed of the motor.

By operating an alarm circuit using the output voltage of the filter 29 described above, it is possible to detect an abnormality in the rotation speed of the motor.

In addition to the drive device described in the above-mentioned embodiments, the following improvements have been made to the drive device disclosed by the applicant in Japanese Patent Application No. 57-131603. In other words, one more voltage feedback loop is provided, and the voltage between each phase is detected from the pulse width modulated current command input to the inverter circuit 13, and each phase voltage is converted into a phase current to generate a pulse width modulation circuit. negative feedback to the input. When the speed monitoring device according to the present invention is applied to this device, the phase-to-phase energization timing circuit can be omitted by utilizing the signal generated in the circuit for detecting the voltage between each phase. This makes it possible to implement the speed monitoring scheme according to the invention with the addition of only a few circuit elements.

Effects of the Invention According to the present invention, the rotational speed of the synchronous motor can be monitored even if the speed signal from the tachogenerator or tachometer encoder is cut off.

[Brief explanation of drawings]

The drawing is a block circuit diagram of a synchronous motor drive device using a synchronous motor speed monitoring system as an embodiment of the present invention. 11... 3-phase AC power supply, 12... Rectifier circuit, 13...
...Inverter circuit, 14...Synchronous motor, 15...
・Valscoder, 16...Tacho generator, 17・
...Speed signal adder, 18...Error amplifier, 19...
・DC/3-phase conversion circuit, 20, 21.22... Current signal adder, 23.24.25... Current amplifier, 26.
...Pulse width modulation circuit, 27... Phase-to-phase energization timing circuit, 28... OR gate, 29... Filter circuit. Patent applicant FANUC Co., Ltd. Patent application agent Akira Aomi Patent attorney Kazuyuki Nishidate Patent attorney Akira Yamaguchi

Claims (1)

[Claims] A speed signal adder that receives a speed command, a DC/3-phase conversion circuit that converts the output of the speed signal adder from DC to 3-phase AC, and 3 that receives the outputs of the DC/3-phase conversion circuit, respectively. three current signal adders, three current signal adders from the current signal adders;
a pulse width modulation circuit that outputs a pulse width modulated signal, an inverter circuit that receives the output of the pulse width modulation circuit, a synchronous motor driven by the output of the inverter circuit, and a synchronous motor coupled to the synchronous motor. The output of the tacho generator is subtracted from the speed signal adder, and the output of the pulse coder is supplied to the DC/three-phase conversion circuit, and the output of the tacho generator is subtracted from the speed signal adder. In a speed monitoring system for a drive device for a synchronous motor, in which signals corresponding to current values of the pulse width modulation circuit and the phase current signal of the synchronous motor are respectively supplied to the current signal adder to be subtracted, The receiver is an inter-phase energization timing circuit for obtaining an inter-phase energization timing signal of the synchronous motor, an OR circuit that receives six output signals from the phase-to-phase energization timing circuit and calculates the logical sum thereof, and an output rectified by the OR circuit. 1. A speed monitoring system for a synchronous motor, comprising: a filter circuit for smoothing the rotational speed of a synchronous motor;