JPS58179188A - Braking method for induction motor - Google Patents

Abstract

PURPOSE:To obtain high brake force in the full speed range without using another DC power source by utilizing a motor drive DC power source for a brake, and DC braking the motor at the low speed time for the induction generative brake. CONSTITUTION:The output voltage V2 of a function generator 17 is lowered at a constant speed by applying a stop signal STP, thereby sequentially decelerating a motor 11. The counterelectromotive force of the motor 11 is presented between lines 12a and 12b through diodes 10a-10f, and when the difference between the output voltage Va of the chopper 2 and the voltage V2 becomes larger than the output voltage V4 of a vias voltage setter 33, a transistor 14 is turned ON by a comparator 31, and the counterelectromotive force is consumed by a resistor 13. The motor 11 is decelerated by the induction generative brake, the voltage Va is switched so as to becomes smaller than the output voltage V5 of a switch voltage setter 37. Then, a timer 21 outputs a signal by the comparator 35 and an AND circuit 38. In this manner, a 3-phase distributor 20 continuously turns ON only transistors 9a, 9f, thereby DC braking the motor 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for braking an induction motor driven by a transistor inverter, in particular according to the PAMC (Pulse Amplitude Modulation) method.

Braking methods for induction motors (hereinafter referred to as motors) driven by transistor inverters include a method of applying braking directly to the rotating shaft using a brake mechanism, as well as
Induction power generation braking and DC braking are known. Induction-powered braking is a method of braking that uses a motor as a generator and consumes the generated power in a resistor, etc., and DC braking
This is a method in which the stator of the motor is excited with direct current and the electromagnetic force is used to brake the rotor.

By the way, induction generation braking can obtain sufficient braking force when the motor rotates at high speed, but has the disadvantage that when the motor rotates at low speed, the induced generation voltage becomes low and sufficient braking force cannot be obtained. On the other hand, in the case of DC braking, the motor is separated from the railroad track and driven by a separate DC power source, which has the disadvantage of complicating the braking circuit.

This invention has been made in view of the above circumstances, and its first purpose is to provide a method for braking a motor that can apply DC braking without providing a separate DC power source. The second object is to provide a method for braking a motor that can obtain high braking force in the entire range from high-speed rotation to low-speed rotation.

In order to achieve the first objective, this invention utilizes the DC power supply for driving the motor for braking, and also uses induction when the motor is rotating at high speed. An embodiment of the present invention will be described below with reference to the drawings, in which braking is applied by dynamic braking and, when the rotation speed is low, by direct current braking.

FIG. 1 is a circuit diagram showing the configuration of the main circuit of a PAM type transistor inverter to which the method according to the present invention is applied, and FIG. 2 is a block diagram showing the configuration of the control circuit of the same transistor inverter. In FIG. 1, 1 is a diode bridge that performs full-wave rectification of a three-phase AC voltage, and the DC output voltage of this diode bridge is supplied to a chopper circuit 2. The chopper circuit 2 includes an input capacitor 3, a transistor 4 inserted in series with the line,
7 Lee wheeling diode 5 and choke coil 6
and an output side capacitor 7, the output voltage Va of which is supplied to the orthogonal/alternating current conversion circuit 8 and also to the terminal 27 shown in FIG. The orthogonal/alternating current conversion circuit 8 is a circuit that converts the direct current voltage Va output from the chopper circuit 2 into a rectangular wave three-phase alternating current voltage, and includes six transistors 9a to 9.
9f, and diodes 10a to 10f inserted in parallel between the emitter and collector of each of these transistors, and the connection point of transistors 9a + 9d,
The alternating current voltage obtained at the connection point of transistors 9b+9'e and the connection point of transistors 9c and 9f is supplied to each motor 11. Further, a resistor 13 and a transistor 14 connected in series are inserted between the positive voltage line 12a and the negative voltage line 12b of the orthogonal/alternating current conversion circuit 8. In this case, the resistor 13 is for consuming the electric power generated from the motor 11 when the motor 11 is being braked by induction braking, and the resistor 13 is for consuming the electric power generated from the motor 11 when the motor 11 is being braked by induction braking.
4 is for turning on/off the current flowing through the resistor 13.

Next, in FIG. 1, the reference numeral 16 is a frequency setter for setting the frequency of the output AC voltage of the orthogonal/alternate conversion circuit 8, and the output voltage Vs is set by the function generator 1.
7. The function generator 17 is
A function to change the output voltage vl to a relatively slowly changing voltage v2 when the output voltage v1 of the frequency setter 16 changes suddenly (that is, when the frequency setter 16 is suddenly operated) and output it. When the stop signal 5TP (, one number in the binary level) is supplied via the terminal 18, from the time when the stop signal 5TP is supplied, the voltage v2 is applied at a constant speed regardless of the value of the '-voltage Vl. This circuit has the function of attenuating the signal to zero. The V/F (voltage/frequency) converter 19 is a function generator 1
This circuit generates a clock pulse CP having a frequency corresponding to the voltage v2 supplied from 7, and the generated clock pulse CP is output to the three-phase divider 20. The three-phase distributor 20 outputs the output power of the timer 21? 0'' signal, six types of rectangular wave signals having the same frequency as the clock pulse CP and whose phases are shifted by / and 2θ° are generated, and each base of the transistors 10a to 10f (7) is generated. On the other hand, when the output of the timer 21 is the □゛1'' signal, for example, only the transistors 9a and 9f are turned on, thereby directing the DC output of the chopper circuit 2 between the two input terminals of the motor 11. Voltage Va is supplied, and DC braking is applied to the motor 11.

Further, reference numeral 22 is a DC braking voltage setter that sets the output voltage of the chopper circuit 2 during DC braking, and its output voltage v3 is supplied to the normally open contact a of the changeover switch 23. The changeover switch 23 is driven when the output of the timer 21 is a "1" signal (during DC braking), and the above-mentioned voltage v2 is supplied to its normally closed contact, and the voltage V2 is supplied to its common terminal C. The voltage applied to the amplifier 25 is supplied to the calculation point 26 of the amplifier 25.

The amplifier 25 receives the output voltage Va of the chopper circuit 2 supplied to the calculation point 26 via the terminal 27 and the changeover switch 23.
It proportionally and integrally amplifies the deviation from the voltage obtained at the common terminal C of , and a series circuit of a capacitor 28 and a variable resistor 29 is inserted in the feedback loop. Then, the transistor 4 of the chopper circuit 2 is controlled on/off based on the output voltage of the amplifier 25. That is, the output voltage v2 of the chopper circuit 2 is a voltage corresponding to the output voltage of the amplifier 25. The 0 comparator 31 subtracts the voltage v2 from the voltage Va supplied to the calculation point 32, and the result of the subtraction is applied to the calculation point 32. Based on the output of this comparator 31, if the output voltage v4 of the asymmetry pressure setting device 33 supplied to the comparator 32 is larger, a 1" signal is output, and if it is smaller, a 0" signal is output. The O comparator 35, in which the transistor 14 is controlled on/off, compares the voltage Va supplied to its calculation point 36 with the output voltage v5 of the switching voltage setter 37, and calculates Va.
> For Vs, the signal is 0, and Va (for Vs, the signal is 1)
It outputs each signal, and its output is AND gate 3
The quad gate 38 supplied to one input terminal of the comparator 35 is a circuit that ANDs the output of the comparator 35 and the stop signal STP, and its output is supplied to the timer 21. timer 2
Reference numeral 1 designates a circuit that outputs a ``1'' signal for a certain period of time after the output of the AND gate 38 rises to the ``1'' signal.

Next, the operation of the circuit shown in FIGS. 1 and 2 will be explained.

First, in the normal operating state, the output of the timer 21 is at the "O" signal, and the frequency setter 1 is output from the three-phase distributor 20.
Six types of rectangular wave signals having frequencies corresponding to output voltage 1 of 6 are output to transistors 9a to 9f, respectively.Thus, a 3-phase AC voltage is supplied to the motor 11, and the motor 11 corresponds to voltage v1. Rotates at the number of revolutions. In this state, when the frequency setter 16 is operated to increase the voltage Vt, the output voltage v2 of the function generator 17 increases accordingly. When the voltage v2 rises, the frequency of the clock pulse CP output from the V/F converter 19 rises, and therefore the frequency of the output signal of the three-phase divider 20 rises, causing the 7-11 to rotate at an even higher speed. Furthermore, when the voltage V2 rises, the output voltage of the amplifier 25 rises, and as a result, the output voltage Va of the chopper circuit 2 rises. Conversely, when the voltage vI is lowered, the frequency of the output signal of the three-phase divider 20 is lowered, and thus,
The motor 11 is decelerated, and the voltage Va also decreases. Note that in the above-mentioned normal operating state, unless the voltage v1 is suddenly and significantly lowered, the output of the comparator 31 will not become ``1'' (, therefore, the transistor 14 is in the off state. Next, the operation during braking will be explained.

When the stop signal 5TP (number 11') is supplied to the terminal 18, this stop signal STP is supplied to the function generator 17 and the AND gate 38 via the terminal 18. Stop signal ST to function generator 17
When P is supplied, the output voltage (2) decreases at a constant speed, and as a result, the motor 11 is sequentially decelerated, and the output voltage Va of the chopper circuit 2 becomes the voltage v2.
motor 11 should decrease (with the descent of motor 11)
is decelerated, a back electromotive force is generated in the stator winding of the motor 11, and this back electromotive force appears between the lines 12g and 12b through the diodes 10a to 10f, and as a result, the voltage Va becomes higher than the original voltage. is maintained at a voltage of When the difference between the voltage Va and the voltage v2 becomes larger than the output voltage v4 of the bias voltage setter 33, the output of the comparator 31 becomes a signal of "1", and as a result, the transistor 14 turns on, and the motor 0 When the back electromotive force generated in the motor 11 is consumed by the resistor 13, the voltage Va decreases. When the difference between the voltage Va and the voltage V2 becomes less than the voltage v4, the output of the comparator 3 becomes the O signal, and the transistor 1
4 is cut off. When the transistor 14 is cut off, the difference between the voltage Va and the voltage v2 gradually increases again, and when this difference exceeds the voltage V4, the transistor 14 is turned on again. Thereafter, processes similar to those described above are repeated.

The above is the deceleration process of the motor 11 by induction power braking. Next, the motor 11 is sequentially decelerated by this induction braking, and the voltage Va is sequentially decreased, and the voltage V
When a becomes smaller than the output voltage v6 of the switching voltage setter 37, the output of the comparator 35 becomes a 1. ? 1" signal.The output of timer 21 is %
When the number 1L/,, is reached, the normally open contact a of the changeover switch 23
and the common terminal C are connected, whereby the output voltage v3 of the DC braking voltage setter 22 is supplied to the calculation point 26 via the changeover switch 23. As a result, from now on, the output voltage Va of the chopper circuit 2 is held at a constant voltage corresponding to the voltage v3. Also, 1 signal is output from timer 21, and 3
Once supplied to the phase divider 20, the three-phase divider 20 subsequently turns on only the transistors 10a and 10f continuously. As a result, the output voltage Va of the chopper circuit 2
(In this case, a constant voltage corresponding to the voltage v3) is then continuously supplied between the two terminals of the motor 11, thereby applying direct current braking to the motor 11 and rapidly stopping the rotation of the motor 11.

Note that when the set time of the timer 21 has elapsed, the timer 21
The output becomes the ゝゝO' command again, but at this time the voltage v2 has already become zero, so the motor ll will not rotate again.

Further, in the above-described embodiment, the transistors 9a r 9f are turned on during DC braking, but this may be, for example, transistors 9+9c.
Alternatively, transistors 9b and 9d.

Transistor 9b, 9f,) transistor 9c + 9
Any combination of a+transistors 9c and 9b may be used.0 As explained above, according to the present invention, since the DC braking is applied using the DC power supply for driving the motor, it is not necessary to take the trouble to provide another DC power supply. However, since the motor is braked using both induction braking and DC braking, high braking force can be applied over the entire range from high-speed rotation to low-speed rotation. Obtainable.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing the configuration of the main circuit of a transistor inverter using the PAM method to which the method according to the present invention is applied, and Fig. β is a circuit diagram showing the configuration of the control circuit of the same transistor inverter. ...Diode bridge, 2...Chopper circuit, 8...
Orthogonal/AC conversion circuit, 11...Induction motor. Applicant Shinko Electric Co., Ltd.

Claims (2)

[Claims] (1) In a method for braking an induction motor driven by an inverter having a DC power supply section and a transistor circuit that transforms the DC voltage output from the DC power supply section into a rectangular wave AC voltage and outputs the converted voltage, the motor is connected to the inverter. After the stop signal is supplied, the output voltage of the DC power supply section is set to a constant voltage, and a predetermined transistor of the transistor circuit is turned on to output the output voltage from the DC power supply section to the stator winding of the induction motor. 1. A method for braking an induction motor, comprising continuously supplying the constant voltage applied to the induction motor, thereby applying braking to the induction motor. (2) In a method for braking an induction motor driven by an inverter having a DC power supply unit and a transistor circuit that transforms the DC voltage output from the DC power supply unit into a rectangular wave AC voltage and outputs the converted voltage, the inverter After the stop signal is supplied, the induction motor is decelerated by induction regenerative braking, and when the rotational speed of the induction motor drops to a predetermined rotational speed, the output voltage of the DC power supply section is set to a constant voltage. At the same time, two predetermined transistors of the transistor circuit are turned on to continuously supply the constant voltage outputted from the DC power source to the stator winding of the induction motor, thereby A method for braking an induction motor, which is characterized by applying braking to the motor.