JPH033689A - Speed controller for dc motor - Google Patents

Abstract

PURPOSE:To improve speed responding performance by setting the responding frequency of a speed control system to a high value at the time of a low speed and to a low value at the time of a high speed. CONSTITUTION:A speed controller of a DC motor 10 is composed of a speed setter 14, a speed instruction unit 16, a speed controller 18, and controls a speed through a thyristor converter 30. The unit 16 has a responding frequency setter 20 and stand speed instruction units 22A-22E. The controller 18 has a speed control circuit 24, a responding frequency altering unit 26 and a field control circuit 28. The gain of the circuit 24 is switched at the times of low and high speeds, and raised at the time of a low speed.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a speed control device for a DC motor, which is suitable for use in a DC motor that requires wide-range, highly accurate, and highly responsive speed control.

[Conventional technology]

There are various types of electric motors, such as DC motors and AC motors, and depending on their output and characteristics, they are used in drive devices for various mechanical equipment. Direct current motors are generally characterized by good speed-torque controllability. For this reason, in machines such as steel cold tandem rolling mills, which have a large capacity, have sudden changes in torque (current), and need to drive each stand at the same speed over a wide range of speed control, conventionally DC An electric motor is used. In recent years, due to the diversification of rolled products and the improvement of their quality,
These DC motors are required to have improved speed control responsiveness. Furthermore, some items require rolling at low speed for a long period of time. Improving the speed response improves the response accuracy of the output monitor automatic plate thickness control (AGC) actuator. In addition, in order to suppress gauge fluctuations during acceleration and deceleration, it is necessary to improve speed responsiveness at each stand to improve speed uniformity. To increase speed response, use automatic L7L! The response frequency ωC of the 1I111 (ASR) system may be increased. In recent years, large-capacity variable speed control of AC motors has become possible. However, when updating only the control system of existing equipment, the object to be controlled is a DC motor. However, in the case of a DC motor, the response frequency ωC of the ASR system
If an attempt is made to increase the speed to 15 rad/s or more, a problem arises in that rectifying sparks occur, and this imposes restrictions even if an attempt is made to improve the speed response. That is, in a DC motor, in order to maintain the torque in the same direction, the armature current must be made into a rectangular wave alternating current whose direction changes periodically. will be held. Therefore,
Due to its structure, it is essentially necessary to rectify the current using a brush, but this rectification imposes restrictions on the speed response. Generally, the higher the speed, the larger the current, and the wider the speed control range of a DC machine, the more difficult rectification becomes. Currently, the value calculated by power (kW) x (speed at high speed (ROM)) 2/(speed rpm at low speed) is 3 to 5 x 10
It is said that the production range is a DC motor of about 6. In addition, the magnetic flux density distribution in the gap of a DC motor is symmetrical when there is no load (when only the main pole magnetic flux exists), but when a load current flows through the armature winding, the influence of the magnetomotive force Distortion occurs in the magnetic flux density distribution, resulting in biased magnetization. This kind of effect that distorts the magnetic flux density distribution is called armature reaction, and armature reaction is heavy and negative. The heavier the load and the weaker the field, the more significant this is. In particular, in DC motors used at high speeds and with heavy loads, or where the load current changes suddenly, a compensation winding is provided at the bottom of the main pole and this is excited by the load current to prevent armature reaction. ing. It has also been practiced to provide a commutative pole on the neutral axis and excite it with a load current to bring the magnetic field near the neutral axis into a state convenient for rectification. In other words, one of the causes of sparks in the brushes of a DC motor is the self-induction that occurs in the armature winding due to rapid changes in the current rate of change (at high speeds) and load current due to current direction switching. Electromotive force (reactance voltage L
-di/dt) at high response time). On the other hand, the interpolation not only corrects the biased magnetic effect near the neutral axis, but also
A voltage that cancels out the reactance voltage is induced during rectification to improve rectification. Further, when a wide range of speed control is required, such as in a mill motor, field weakening control is performed in addition to armature voltage control. When field weakening control is performed, the magnetic flux of the main pole is weakened at high speeds, making the influence of armature reaction even stronger. Furthermore, the improvement in speed responsiveness increases the current change rate di/dt, which increases sparks during commutation.

[Problem to be achieved by the invention]

However, as mentioned above, the conventional technique of improving the armature reaction using interpolation, etc. can only maintain the current speed response of the DC motor, and improve the speed response without being constrained by commutated sparks. The problem was that it was difficult to do so. The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to provide a speed control device for a DC motor that can improve the speed response performance of the DC motor without being restricted by rectified sparks. do.

[Means for achieving the object 1] The present invention solves the above problem by providing a speed control device for a DC motor with means for setting the response frequency of the speed control system low at high speeds and high at low speeds. This has been achieved. [Function] In a DC motor, the rectification limit is the current change rate di/d
Since it is determined by t, the higher the speed and the larger the current, the more difficult rectification becomes, but the limit at low speeds is considered to be high. Therefore, in the present invention, the response frequency of the speed control system of the DC motor is set to be high at low speeds and low at high speeds, thereby increasing speed responsiveness at low speeds. Therefore, the speed response performance in the low speed range of DC 74aN can be improved without being restricted by rectifying sparks. [Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this example, tandem rolling 11 (
In the speed control device of the DC motor type 10 shown in Fig. 1, which is used to control the drive of a stand (5 stands), the response frequency ωC is changed between low speed and high speed, and rectification becomes a problem in the low speed range. Speed control (ASR) described below to the extent that
The gain of the circuit 24 is increased to improve the response frequency at low speeds. As shown in FIG. 1, this speed control device includes a speed setting device 14 for the operator to set the line speed (main speed) on a pull bit operating table while checking the machining status displayed on the CRT 12; Set line speed MRH
, a speed command section 16 for determining the speed command of the DC electric motor 10 and the response frequency ωC according to the schedule for each stand, and a speed control unit 16 for determining the speed of each stand, that is, the speed of the DC motor 10, based on the determined speed command. It mainly includes a speed control section 18 that performs the following. The speed command unit 16 has a set line speed MRH.
A response frequency setter 20 for calculating a response frequency ωC from the line speed MRH, and stand speed command units 22A to 22E for calculating speed commands 5SRHI to 5SRH5 for each stand from the line speed MRH according to a schedule are provided. The speed control unit 18 has a set stand speed 5S.
A speed control 0 (ASR) circuit 24 for controlling the speed of the DC motor 10 of the stand according to RHI~5SRH5, and a speed control circuit 24 for changing the response frequency of the speed control circuit 24 from the set response frequency ωC. Response frequency changer 26 and set speed control commands 5SRH1 to 5SR
According to H5, a field control circuit 28 for controlling the field current of the DC motor 110 is provided. In addition, this speed control unit 18 controls each stand (No. 1 to No. 0.5).
provided for each. The DC motor 10 is provided with a thyristor conversion device 30 in its power supply section, and the input power, frequency, etc. are controlled by the speed control circuit 24. The DC motor 1
0, the rotation speed is detected and the speed control circuit 24
a pulse generator (PLG) 32 for input to the
A field winding 33 that generates field magnetic flux is provided. Note that the DC electric motor 110 has a capacity of, for example, 5000 (
kW) can be used. A data transmitter 34 and a data transmission line 36 are provided between the speed command section 16 and the speed control section 18 for transmitting response wave number and speed command signals. For this transmission line 36, for example, an optical link transmission line made of an optical fiber can be used. The speed command unit 16 includes, for example, a control calculation (direct digital controller: DDC) with a calculation period of 20 m5.
) can be used. Further, for the speed control circuit 24, for example, one having a calculation cycle of 4 ms can be used. The effects of the embodiment will be explained below. In this embodiment, in order to control the speed of each stand, the line speed MRH is first set using the speed setting device 14. In the speed command unit 16, the response frequency setter 20 calculates the response frequency ωC to be commanded according to the set line speed MRH, and the stand speed command units 22A to 22E calculate the schedule for each stand. The speed commands 1i1SSRH1 to 5SRH5 are calculated and set accordingly. At this time, the calculated response frequency ωC is variable depending on the line speed. For example, as shown in Figure 2, the response frequency ωC is based on the line speed.
25rad/ until reaching speed 197 (rpfit)
15 rad/s without changing as s, beyond the 197 rom to a top speed of 591 rpm.
S can be gradually reduced as a target. The set response frequency ωC and stand speed command values 5SRHI to 5SRH5 are input to the speed control section 18 via the data transmission path 34. In the speed control section 18, the response frequency changer 26 changes the gain of the speed control circuit 24 based on the transmitted data of the response frequency ωC. Further, the input speed commands 5SRHI to 5SRH5 are transmitted to the speed control circuit 24 and the field control circuit 28. The speed control circuit 24 receives these speed commands 5SRHI to 5S.
Comparing RH5 and the actual speed detected by PLG 32, a current command is output to thyristor converter 30 so that DC electric motor R10 has a speed corresponding to speed commands 5SRH1 to 5SRH5. The thyristor converter 30 controls the supplied current according to the current command, and the field control circuit 28 controls (for example, weakens) the field current according to the commands 5SRHI to 5SRH5. In this way, the speed of the DC electric motor R10 of each stand is controlled (increased). By the way, the rectification limit of the DC motor 10 is the current change rate di
/dt, so there is a limit at high speeds and large currents, but the limit at low speeds is considered to be high. Therefore, in this embodiment, the gain of the speed control circuit 24 is switched between low speed (e.g., base speed) and high speed (e.g., top speed), and the speed control gain is adjusted to the extent that rectification does not become a problem at low speed. In order to increase the speed, the response frequency ωC is set high at low speeds and low at high speeds, as shown in FIG. Furthermore, an issue to be considered in variable control of the response frequency ωC is how to associate the motor speed with the gain of the speed control circuit 24. If a gain is associated with each speed in the speed control circuit 24 of each stand, the speed command 5SRH
Due to the difference in I~5SRH5, a problem arises in that the response varies from stand to stand. Therefore, a gain corresponding to the response frequency ωC is set in the speed control circuit 18 by the speed command unit 16, and the gain used for the speed control calculation is changed. The calculation cycle of the speed command section 16 is 20IllS, and the acceleration/deceleration time is 15 seconds at 0-TOP speed (maximum speed). Also, the gain change range is 25 rad/speed at low speed.
Since the speed is 15 rad/s at S1 high speed, the gain can be changed sufficiently smoothly. As a result, no sparks were generated in the brushes of the DC motor in the entire speed range, and the speed response at low speeds was improved by increasing the response frequency at low speeds. Further, a tandem rolling mill was controlled by a speed control device embodying the present invention to perform high-speed rolling. At this time, for comparison, we used a conventional speed control device (speed response frequency is constant over the entire speed range and 15ra).
When rolling was performed by controlling a tandem rolling mill at a speed of d/s), the plate thickness variation was 1.0% on average with respect to the target plate thickness. On the other hand, the control device of the present invention (at low speed of 25 rad/
In the tandem rolling mill controlled by s), the plate thickness variation is 0.
improved to 95%. Further, in this case, due to the improvement in speed response, there was no effect in the case of spark generation or deterioration of current performance. In the above embodiments, an example in which the present invention is implemented in a steel cold tandem rolling mill has been described, but the speed control device for a DC motor in which the present invention is implemented is not limited to such a configuration. The present invention can also be applied to the control of other large DC motors that require uniform speed.

【effect】

As explained above, according to the present invention, the speed response of the DC motor is not restricted by rectified sparks, and the speed can be controlled, and the speed response at low speeds can be increased, which is an excellent effect. is obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall configuration of a speed control device according to an embodiment of the present invention, and FIG. 2 is a line showing an example of response frequency characteristics with respect to line speed for explaining the operation of the embodiment. It is a diagram. 10... DC motor, 14... Speed setting device, 1
6...Speed command section, 18...Speed control section, 20
...Response frequency command device, ωC ...Response frequency, 22A~22E...Stand speed command device, 24.! I
f control M! (ASR>1!, 26... Response frequency changer, 28... Field control circuit, 30... Thyristor converter, 32.-PLG, 34... Data transmission line.

Claims (1)

[Claims] (1) A speed control device for a DC motor, comprising means for setting the response frequency of the speed control system of the DC motor to be low at high speeds and high at low speeds.