JP3052390B2 - Reversible thyristor Leonard switching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current switching method for a reversible thyristor leonard having a function of switching a current direction of a DC motor, which is supplied to a DC motor after being converted to DC by an thyristor from an AC power supply. The present invention relates to a current switching method for a reversible thyristor leonard that can stably switch the current direction of a motor even in a load with a small torque and with a short switching time.

[0002]

2. Description of the Related Art A conventional circuit example of a reversible thyristor leonard having a current direction switching function of a DC motor having a current minor loop will be described with reference to FIG. FIG. 3 shows an example of a reversible thyristor leonard having a function of switching the current direction of a DC motor having a speed control circuit with a current minor loop. When the rotation direction of the DC motor is switched, current flows through the thyristors in both directions. FIG. 4 is a block circuit diagram showing a main part of a non-recirculating reversible thyristor leonard that temporarily cuts a thyristor.

In FIG. 3, A is an AC power supply, 1 is a DC motor, 2 is a plurality of thyristors in a bridge connection for supplying a forward current, and 3 is a bridge connection for supplying a reverse current to the DC motor 1. Reference numeral 4 denotes a rotation speed detector for detecting the rotation speed of the DC motor 1.

[0004] Reference numeral 5 denotes a current transformer.
Circuit current obtained at a predetermined ratio by the current detector 6
Is converted into a signal value indicating the magnitude of the circuit current.

[0005] Reference numeral B denotes a speed reference signal for instructing the rotation speed of the DC motor controlled and driven by the reversible thyristor leonard. The speed reference signal B input to the reversible thyristor leonard is compared with a signal indicating the rotation speed of the DC motor detected by the rotation speed detector 4 by the differential circuit 11, and the detected deviation signal is calculated by the operational amplifier circuit 13. After being converted into a current command value, the signal value indicating the magnitude of the circuit current obtained by the current detector 6 is compared with the differential circuit 14, and the detected deviation signal is used as a current control value having a PI function. After being integrated and amplified by the amplifier 30, it is input to the phase control circuit 16.

The signal value output from the current command polarity detector 19 and the signal value output from the zero current detector 18 determine whether the polarity of the ignition thyristor corresponding to the motor current direction of the DC motor 1 is switched or not. It is input to a forward / reverse switching logic circuit 15 for determining a thyristor gate cutoff time, and the output signal from the forward / reverse switching logic circuit 15 and the firing phase of the thyristor of the phase control circuit 16 are converted into a forward / reverse trigger pulse generator. 17, a gate trigger pulse of a predetermined thyristor is generated and input to a predetermined gate of the thyristor 2 or the thyristor 3, and a current flows to the DC motor 1 according to the current command polarity signal.

Reference numeral 18 denotes a zero current detector for detecting that the current value initially flowing attenuates to a predetermined value so that the thyristor 2 and the thyristor 3 do not fire at the same time when switching the thyristor forward / reverse bridge. Reference numeral 19 denotes a current command polarity detector which determines a polarity by inputting a current command to determine the polarity of the forward / reverse bridge of the thyristor, but includes a control signal circuit and a DC power supply line supplied to each circuit. The illustration other than the basic element circuit for explanation is omitted.

[0008]

In order to reverse the current direction of the DC motor 1 in the above-described circuit configuration,
In accordance with the current command signal of the thyristor leonard, the current is attenuated with respect to the load by setting the phase angle of the gate trigger pulse of the thyristor that has been ignited until then to the kick position, and the circuit current becomes almost zero when the current becomes zero. When the detector 18 detects the thyristor, the output of the gate trigger pulse of the thyristor that has been fired is stopped, and after a lapse of a predetermined time, the gate trigger pulse of the thyristor to be fired next is changed according to the current command polarity signal. The thyristor is prepared with a phase in accordance with a predetermined condition in the circuit, and supplied to the thyristor. Therefore, the thyristor is fired and a current flows in the direction of the current command polarity.

However, when the current command value output from the operational amplifier circuit 13 when switching the motor current direction is small and the phase angle of the gate trigger pulse with respect to the thyristor to be fired is large, the output voltage value is high. If it is larger than the back electromotive force from the DC motor as a load, the motor current does not flow, the command signal value increases due to the integration function of the current control amplifier, and the phase angle of the gate trigger pulse for this thyristor advances. The motor current flows when the voltage value output from the thyristor decreases and the back electromotive force from the DC motor as a load wins.

That is, as shown in the time chart of FIG. 4, at the timing t1, the current command polarity detector 19
, The current starts to decrease due to the shift of the gate trigger phase of the thyristor in the direction of the kick position. At a timing t2, the current value matches a predetermined set value α, and a delay signal is activated. Even if the delay signal times out and a trigger pulse is sent to the gate of the next thyristor, if the current command value is small, the current does not rise until timing t4.

That is, when the current command value is small, the input of the current control amplifier is small, so that a large delay time occurs for the phase angle to advance, and therefore, there is a problem that the delay time greatly varies depending on the load condition. For example, as described above, the switching dead time after the detection that the current has become zero is about 5 milliseconds from timing t2 to t3, and the switching dead time extends to timing t4. May be required.

As a countermeasure, a means may be used to accumulate a constant value in the integrator and output the same at the timing t3. However, depending on the load and disturbance conditions, the current may flow too much and hunting or excessive current may occur. There is a problem that the current protector works.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a reversible thyristor capable of changing a motor current direction so that a large delay time does not occur when switching the current direction of a motor and a delay time does not exceed a predetermined value depending on a load condition. An object of the present invention is to provide a method for switching the current of Leonard.

[0014]

In order to solve the above-mentioned problems, in this method for switching the current of the reversible thyristor leonard, in the forward / reverse rotation speed control of a DC motor having a current minor loop including a PI control function, the forward / backward rotation is controlled. A non-recirculating reversible thyristor that outputs a gate trigger pulse for energizing the other thyristor converter a predetermined time after the current of one of the thyristor converters that has been flowing decreases to a predetermined value near zero, In the Leonard forward / reverse switching method, after the predetermined time, a fixed voltage value is input to the integrating amplifier of the current PI control function, which is configured by connecting a proportional amplifier and an integrating amplifier in parallel, instead of the regular current deviation signal. After accelerating the integration and detecting the circuit current value of the other thyristor converter, the input of the integrating amplifier for this PI control function is connected to the normal current bias. To quickly rise in current at the time of forward and reverse switch by returning the value, and characterized in that so as to reduce the dead time of the switching.

[0015]

As described above, in the forward / reverse switching method of the reversible thyristor leonard according to the present invention, at the time of forward / reverse rotation, the circuit current of one of the thyristor converters which has been flowing so far decreases to a predetermined value near zero. After a predetermined time from
After a fixed voltage value is input to the integral amplifier of the I control function to accelerate the integration and the circuit current value of the other thyristor converter is detected, the input of the integral amplifier of the PI control function is converted to a regular current deviation signal. Since it is set back, the rise time of the motor current at the time of forward / reverse switching becomes less than a certain value,
The current does not flow too much to the motor. In addition, even when the current command value is small, the delay time becomes equal to or less than a certain value when the motor rotates in the normal or reverse direction, and the motor can be stably reversibly controlled.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a method for switching the reversible thyristor leonard between forward and reverse according to the present invention will be described in detail with reference to FIGS. FIG. 1 is a block circuit diagram showing one embodiment of a method and an apparatus for switching a reversible thyristor leonard in accordance with the present invention, and shows a current having a PI control function shown in FIG. Symbols indicating each element circuit are common except for the control amplifier 30,
Elements other than the basic element circuits for explanation, such as a control signal circuit and a DC power supply line supplied to each circuit, are omitted.

In FIG. 1, reference numeral 20 denotes an analog switch circuit which is operated by a signal from a forward / reverse switching logic circuit 15 and which is operated by a circuit b.
, A parallel amplifier 21 and an integrating amplifier 22 mainly composed of a capacitor are connected in parallel to constitute a current control amplifier having a PI control function.

When the analog switch circuit 20 is connected to the circuit a, a bias signal voltage C having a predetermined magnitude determined and determined according to the use and conditions of the motor system is input.

Accordingly, since the bias signal voltage C is integrated by the integrating amplifier 22, when the analog switch circuit 20 is connected to the circuit a, the current control amplifier outputs a ramp-shaped signal having a predetermined rising speed. The signal is added to the output of the proportional amplifier 21 and output.

The zero current detecting circuit 18 detects a reference voltage value α having a predetermined magnitude determined and determined according to the use and conditions of the motor system, as will be described later. Is compared with the reference voltage value α, and a match signal is input to the forward / reverse switching logic circuit 15.

The operation of the present invention in the configuration of the forward / reverse switching logic circuit 15 will be described with reference to a schematic flowchart shown in FIG.

In FIG. 2, during operation of the motor system having the reversible thyristor leonard, the zero current detection circuit 18 compares the voltage value ι output from the current detector 6 indicating the current value of the circuit with a reference voltage value α. However, during normal operation, even if zero current detection operates, operation continues in the same current direction unless the current command polarity is switched.

When the polarity of the current command polarity switching command and the deviation signal output from the differential circuit 14 become negative in step 1, the forward / reverse trigger pulse generator 17
Is shifted in the kick position direction. Accordingly, when the thyristor current attenuates and the voltage value ι proportional to the circuit current value becomes smaller than the reference voltage value α, in step 3, the gate trigger pulse for each thyristor output from the forward / reverse trigger pulse generator 17 is output. The output is cut off, the integrated amount of the current control amplifier is set to the value of the kick position, and the timer starts counting. In step 4, the count time t of the timer is determined and determined according to the use and conditions of the motor system. Time τ having a predetermined size, for example, 5
In milliseconds, in step 5, the thyristor to be checked again by checking the current command polarity signal, that is, the current direction of the motor is checked again, and the forward / reverse trigger pulse generator 1 is checked.
7 to output a gate trigger pulse to each thyristor.

Next, in step 6, the analog switch 20 is switched to the a side, and a voltage C having a predetermined magnitude determined according to the use and conditions of the motor system is input to the integrating amplifier 22.

That is, since the integration is accelerated, the rise of the output voltage of the current control circuit is advanced, so that the trigger phase of the trigger pulse from the forward / reverse trigger pulse generator 17 to the target thyristor is advanced earlier. Therefore,
The thyristor current rises at a fast rate.

After the above operation, in step 7, when the thyristor voltage becomes a voltage that can oppose the back electromotive force of the load, a circuit current starts to flow, and the current value obtained by the current transformer 5 and the current detector 6 When the zero current detection circuit 18 detects that the proportional voltage value ι has become larger than the voltage α having a predetermined magnitude determined according to the use and conditions of the motor system, the forward / reverse rotation is performed in step 8. The output of the logic circuit 15 switches the analog switch 20 to the b side. Accordingly, since the operational amplifier 21 and the integrating element 22 make use of the integration function of the current control amplifier constituting the PI control function, the output phase of the gate trigger pulse is output in a phase according to the condition of the output signal of the differential circuit 14. Become like

Since the PI control function of the current minor loop is restored as described above, the current flows in a new current direction while performing the current control, and the switching of the current direction is completed.

In the above-described embodiment, the voltage value fixed to the integrating amplifier of the PI control function after a predetermined time after the current of the thyristor converter that has been flowing so far at the time of the forward / reverse switching is reduced to a predetermined value near zero. To accelerate the integration, and after detecting the circuit current value of the other thyristor converter,
Since the input of the integrating amplifier having the I control function is returned to the normal current deviation signal, the rise time of the motor current is reduced to a certain value or less, and many excellent effects can be obtained.

The above description of the block circuit diagram and the flow chart diagram is one embodiment for realizing the current switching method of the reversible thyristor leonard according to the present invention.
Other circuits may be configured in accordance with the division of functions between the processing in the computer and the processing by the hardware circuit, and the conditions of the thyristor leonard system, and a flow based on the circuit configuration may be followed.

Although the circuit current has been described as being detected by the AC circuit, the circuit current may be detected at any place where the thyristor current can be detected.

[0031]

As described above, according to the present invention, the current of one thyristor converter, which has been flowing, decreases when the motor is switched between normal and reverse rotations, and the current decreases to a predetermined value near zero. After a predetermined time from, a fixed voltage value is input to the integration amplifier of the PI control function to accelerate the integration, and after detecting the circuit current value of the other thyristor converter, the input of the integration amplifier of the PI control function is normalized. Since the current deviation signal is returned, the following excellent effects can be obtained. Motor current rise time has fallen below a certain value. No excessive current flows through the motor and no hunting occurs. Therefore, even when the current command value is small when the current direction of the motor is changed, a large delay time does not occur in the current direction conversion of the motor. Further, the delay time does not become longer than a certain value depending on the load condition, and the motor current does not flow excessively or hunting does not occur. Therefore, the current direction of the motor can be converted stably under any conditions.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing a main part of one embodiment of a rotation direction switching method of a reversible thyristor leonard according to the present invention.

FIG. 2 is a schematic flowchart illustrating the operation of the current switching method of the reversible thyristor leonard according to the present invention in the block circuit diagram shown in FIG. 1;

FIG. 3 is a block circuit diagram showing a conventional example of a reversible thyristor leonard having a motor current switching function.

FIG. 4 is a time chart illustrating a problem that occurs when current is switched in the conventional reversible thyristor leonard shown in FIG. 3;

[Explanation of symbols]

 1: DC motor 2: Forward thyristor converter 3: Reverse thyristor converter 4: Rotational speed detector 5: Current transformer 6: Current detector 17: Forward / reverse trigger pulse generator 18: Zero current detector 19: Current command polarity detector 20: Analog switch 21: Proportional amplifier 22: Integral amplifier A: AC power supply B: Speed reference signal C: Reference voltage

Claims (1)

(57) [Claims] 1. A forward reverse speed control of a DC motor with a current minor loop including the PI control functions, normal and reverse rotation switching
When the current of one thyristor converter that has been flowing at the time of replacement has decreased to a predetermined value near zero , the other thyristor converter has been switched to the other after a predetermined time.
Positive acyclic reversible thyristor Leonard for outputting a gate trigger pulse for energizing the square of the thyristor converter
In the reverse switching method, after the predetermined time, the proportional amplifier and the integrating amplifier are connected in parallel.
Normal to the integrating amplifier of the PI control function configure continue to
Input a fixed voltage value instead of the current deviation signal to add integration.
After detecting the circuit current value of the other thyristor converter, the input of the integrating amplifier of this PI control function is changed to a regular current.
By returning to the deviation signal , the current
A forward / reverse switching method for a reversible thyristor leonard, characterized in that the rising time is shortened and the dead time of switching is reduced .