JPH02285990A - Direct current motor speed control method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides power converting means 2 & Il connected in antiparallel to each other and connected to the armature of a DC motor, so as to correspond to the required torque of the DC motor. , relates to a speed control method for a DC motor in which these two sets of power conversion means are switched.

[Conventional technology]

FIG. 3 is a bronch diagram showing a conventional example in which the speed of a DC motor is controlled by two sets of power converters connected in antiparallel.

In FIG. 3, the power converters connected in antiparallel to each other, that is, the forward converter 3F and the reverse converter 3R, both convert AC/X power from AC power a2 into DC power, and convert the AC/X power from AC power a2 into DC power. The motor 4 is driven, and the speed of the DC motor 4 is controlled in the following manner.

That is, the speed setting value output from the speed setter 11 is converted into a speed command value that changes at a predetermined rate of change by the acceleration/deceleration calculator 12, and this speed command value and the speed transmitter 13 coupled to the DC motor 4 are The actual speed P and value to be output are manually inputted to the speed jJ1 node which is composed of a proportional-integral calculator. The speed adjustment 2S14 outputs a current command value that adjusts the deviation between these two human forces to zero.

The current regulator 16, which is composed of a proportional-integral calculator, manually inputs the above-mentioned current command value and the actual current value of the DC motor 4 detected by the current detector 15, and makes the deviation between the two manual inputs zero. A control signal is output to the firing angle regulator 17.

The operation command calculation circuit 21 manually inputs the operating conditions, the speed setting value, and the output of the acceleration/deceleration calculator 12, and sends an operation command signal to the switching command calculation circuit 22. Depending on the command signal, either the forward converter 3F or the inverse converter 3R is selected. As a result, the gate drive circuit 18F for the forward converter 3F or the inverse converter 3R
The firing angle adjuster 1 is connected to one of the gate drive circuits 18R for
A firing angle signal is sent from 7. At the same time, an operation command 61 is sent from the circuit 21 to the acceleration/deceleration calculator 12.

By the way, as mentioned above, the current regulator 16 performs an adjustment operation to make the deviation between the current command value and the current actual value zero, and the current command value input to this current regulator 16 is the one that controls the DC motor 4. It has already been explained that this is the output signal of the speed regulator which performs an adjustment flfl operation to make the deviation between the speed command value and the actual speed value zero.

Therefore, when the direct 2It electric [4] is driving a rolling mill for rolling wire rods, the moment the steel material is bitten into the rolling mill or the moment the steel material is extracted from the rolling mill, there is a sudden This causes severe load fluctuations. Due to this sudden load disturbance, the current command value output by the speed regulator 14 changes abruptly in a step-like manner, so that a current with a correspondingly large rate of change flows through the DC motor 4. Become. In the direct/Jt motor 4, when the rate of change dl/dt of the flowing current becomes excessive,
Since this may cause a major accident such as franchise over, it is necessary to suppress this current change rate d I/d L within a predetermined value.

Therefore, as shown in the conventional example circuit in FIG. The configuration is such that the tit command value is changed or limited, and the current change rate dl/dt of the DC motor 4 is kept within a predetermined value. Here, 24 is a suppression setting resistor for setting the slope of the suppression signal outputted by the suppression circuit 23 to a gentle rate of change in the IIT current transmission ratio that is allowable to the above-mentioned DC motor 4.

FIG. 4 is an operation waveform chart showing changes in the current command value in the conventional example circuit shown in FIG. 3, in which FIG. Regarding the operation of the converter 3R, FIG. 4 (c) shows changes in the current command value input to the current regulator 16, respectively.

FIG. 4 shows a case where the DC motor 4, which is in continuous operation, is not switched to the braking operation mode in response to a sudden change in load. That is, at time T1 during forward driving with the forward converter 3F turned on,
When the forward converter 3F is turned off, the 1i style seventh value gradually decreases to zero due to the action of the suppression circuit 23, but the degree of this decrease is determined by the suppression setting resistance as described above. 24, the inverter 3R is turned on at time T, and the current command value is increased at the same slope according to the setting of the suppression setting resistor 24 to enter a braking operation state.

[Problem to be solved by the invention]

By the way, the time T when the forward converter 3F is turned off.

If the interval between T2 and the time point T2 when the inverter 3R is turned on is short, the integral calculator forming the suppression circuit 23 will not complete the discharge, that is, the appropriate ttaH3R will be turned on before the current command value decreases to zero. Therefore, a suppressing effect cannot be obtained.However, increasing the rate of change of the current command value will have an adverse effect on the DC motor 4. Therefore, it is unavoidable to take a sufficient amount of time from T1 to T2, but this makes it difficult for the DC motor 4 to quickly change its operating mode in response to load fluctuations, which reduces the accuracy of speed control. It has major drawbacks that cannot be improved upon.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to improve speed control accuracy by quickly switching operation modes in response to load fluctuations of a DC motor.

[Means to solve the problem]

In order to achieve the above object, the speed control in method of the present invention connects the power conversion means of 2 & Is there a configuration constraint that inputs the ta control loop into the ta control loop? n
In the method of controlling the speed of the DC motor by selecting and controlling one of the power conversion means of 2&fl using a device, a suppressing means constituted by an integral calculator and an output of the suppressing means are provided. In response to this, the control device is provided with means for limiting the current command value output by the speed control loop, and when switching the power conversion means, the power conversion means in operation is turned off at the same time. The suppressing means is held at zero, and then when the other power conversion means is turned on, the zero hold is released, and the suppressing means outputs a signal that increases at a predetermined rate of change.

[Effect]

This invention switches between a forward converter and an inverse converter that supply power to the DC motor in accordance with the operating mode of the DC motor, but when one converter is turned off,
By quickly reducing the current I command value to zero, turning on the other converter, and then increasing this current command value at a predetermined rate of change, it is possible to control the period during which both converters are simultaneously off. The purpose is to shorten the power and improve speed control performance.

〔Example] FIG. 1 is a circuit diagram showing an embodiment of the present invention.

In FIG. 1, the speed regulator 14, which is composed of a proportional-integral calculator, manually inputs a speed command value and an actual speed value, and outputs a current command value that makes the deviation between these two manual forces zero,
Current UR node unit 6, which is also composed of a proportional-integral calculator
The method is to manually input this current command value and the actual current value and output a control signal to the firing angle regulator 17 that makes the deviation between the two manual inputs zero, and to prevent sudden changes in the current I command value. A limiter 25 for limiting the speed regulator 14 and the current regulator 1
6, and that the suppression circuit 23 that sends a signal to the limiter 25 and the suppression setting resistor 24 are layered in the same way as in the conventional example circuit already described in FIG. It is.

In the present invention, a zero hold contact 30 is provided in the suppression circuit 23 made up of an integral calculator, and the zero hold contact 30 is turned on and off by commands from the switching command calculation circuit 22.

That is, when the direct fL electric motor 4 is in continuous operation with the power from the forward converter 3F and the operation mode is switched to braking operation due to a sudden change in load, etc., the operating forward converter 3F is first switched. It is turned off by a command from the command calculation circuit 22, and at the same time, the zero hold contact 30 is turned on by a command from the switching command calculation circuit 22. the result,
The suppression circuit 23 is held at zero and rapidly reduces the current command value to zero.

Next, the inverter 3R is turned on, and at the same time, the zero hold contact 30 is turned off.

Therefore, since the output of the suppression circuit 23 rises gently with a slope according to the setting value of the suppression setting resistor 24, the rate of change of the current command value also slopes accordingly. Therefore, the rate of change of the current flowing through the DC motor 4 becomes excessive, and problems such as generation of sparks and flashover can be prevented.

FIG. 2 is an operation waveform diagram showing the operation of the embodiment circuit shown in FIG. 1, in which FIG. 2(A) shows the operation of the forward converter 3F, and FIG. Regarding the operation, FIG. 2(C) shows the changes in the current command value input to the electric 2IT controller 16, respectively.

As is clear from FIG. 2, the current command value rapidly decreases to zero due to the action of the zero hold contact 30 as the forward converter 3F turns off at time T, and the current command value rapidly decreases to zero due to the action of the zero hold contact 30.
It has been rising slowly since time T, when it turns on.

Therefore, T, to T! Even if the time until the switching is short, the integral calculator 23 forming the suppressing circuit 23 has completely discharged, so that a sufficient suppressing effect can be obtained at the time of switching.

[Effects of the Invention] According to the present invention, when switching the forward/inverse converter, the current command value is rapidly brought to zero by zero-holding the suppression circuit, and the rise of the current command value after switching is maintained at a predetermined level. Since the circuit is configured to gradually increase at a rate of change of , it is possible to shorten the time it takes to switch the converter again, and the operation mode can be quickly switched without losing the suppression effect, improving speed control accuracy. Get effects that can improve.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is an operation waveform diagram showing the operation of the embodiment circuit shown in Fig. 1, and Fig. 3 shows two sets of anti-parallel connected power supplies. FIG. 4 is a block diagram showing a conventional example in which the speed of a DC motor is controlled by a converter, and FIG. 4 is an operation waveform diagram showing changes in the current command value in the conventional example circuit shown in FIG. 2... AC power supply, 3F... forward converter, 3R... reverse converter, 4... DC motor, 11... speed setting device,
12... Acceleration/deceleration calculator, 13... Speed transmitter, 1
4... Speed tA node device 15... Tl flow detector, 16
... Current regulator, 17... Firing angle regulator, 18F,
18R... Gate drive circuit, 21... Driving command calculation circuit, 22... Switching command calculation circuit, 23... Suppression circuit, 24... Suppression setting resistor, 25... Limiter, 30
・・・Zero Ho 144 scale instrument name 2 Figure man 1 Figure Atsushi 4 Figure

Claims (1)

[Claims] 1) Two sets of power conversion means connected in anti-parallel to each other are connected to the armature of a DC motor, and a control device configured to input a current command value outputted by a speed control loop to the current control loop controls the two sets of power conversion means. In the method for controlling the speed of the DC motor by selecting and controlling one of the power conversion means, a suppression means constituted by an integral calculator; The control device is provided with means for limiting a current command value output by the speed control loop, and when switching the power conversion means, the suppression means is held at zero at the same time as one of the power conversion means in operation is turned off. Then, when the other power conversion means is turned on, this zero hold is released, and the suppressing means outputs a signal that increases at a predetermined rate of change.