JPS58108986A - Controller for motor - Google Patents

Abstract

PURPOSE:To enable to rotate a motor even in a low speed range by varying the depending rate in response to the rotating speed of the motor. CONSTITUTION:A depending rate calculator 56 inputs the outputs of a rotating speed detector 54 and a current detector 55, thereby varying the depending rate d between the motor current and the rotating speed in response to the rotating speed. After a speed reference value Na is corrected by a speed correction signal from the calculator 56, it is inputted to a speed controller 53. The controller 53 controls the output of a power source 52, thereby controlling the speed of a motor 51. In this manner, depending characteristic is provided in the low speed range without stopping the motor

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to so-called Droop control of an electric motor that gives drooping characteristics to the rotational speed of the electric motor.

FIG. 1 is an explanatory diagram showing a rolling equipment having two stands.

In the figure, 11) is the material to be rolled, (11) is the work roll of the &)l stand, (6) is the backing roll of the 1) stand, 斡 is the reducer connected to the work roll aυ, and 04 is the reducer This is an electric motor connected to Ql.

Also, (2), @, @, the axes are from Nagi 2 stand, respectively (b) is the work roll, (2) is the backup roll, (
(to) shows the reducer, and (2) shows the electric motor.

In ξ, the speed of the rolled material f1) downstream of the first stand is Y
l p hh The speed of the rolled material (1) downstream of the 2nd stand is Vle, the work roll Ov, the roll diameter of (2) is C and to, the reduction ratio of reducer 01, @ is Q and false, the electric motor a◆,■
The number of rotations per unit time, that is, the rotation speed of N1 and N
,.

Further, if the advance rate of each stand is fl and f2, the following equation holds true.

N, = river...
0 formula% formula% With this ξ, Ih5D+sG1*G! l is a fixed value in a certain rolling state, and fl * fl * vl e vl is also a value for determining the rolling schedule.

Therefore, the rolling schedule is determined based on Nl*l'G.

Now, if Nl is set high, Nw,l
A large load will be applied to the l-stand electric motor 04, and the Oni 2 stand will be pushed through the roll Qυ and the rolled material (11) of the Nagi 1 stand.
The load current of the electric motor member of the Nagi 2 stand becomes small, and the load on both stands becomes unbalanced.

In order to eliminate such a problem, in conventional equipment, as shown in FIG. 2, a drooping characteristic is provided between the motor current I and the motor rotational speed FIN.

Finally, even if the speed reference value Na is set to a high value, as the current increases, the rotation speed 1tNb is automatically controlled to become smaller.

In conventional equipment, the rate of rotational speed droop is constant with respect to load current, and in Figure 2, the rated rotational speed of the motor is set to N.
o The speed reference value is Na, and the speed change speed reference value Na is the rotational speed of the motor when the rated load current Io is applied during rotation.
b, the drooping rate 1d is defined by the Kawa-0 equation. In the conventional device, this drooping rate d was unrelated to the speed, so there were problems as described below.

That is, in the low speed region, for example, the speed reference value is Na)
od and when the load current of the motor exceeds the rated current, the speed reference is canceled by the droop correction circuit, and the motor stops rotating, as if the speed command were zero.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and provides a control device that enables rotation even in a low speed region by changing the droop rate d according to the rotational speed of the electric motor. is intended to provide.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 8, tti1+ is the controlled electric motor, 1
Power supply device for driving the 5'A4'A electric motor,・
A is a speed controller, - is a rotational speed detector that detects the rotational speed of the electric motor (2), - is a load current detector that detects the load current of the electric motor 1511, - is a drooping rate calculation device, and Sae is a speed command signal are shown respectively.

Next, the operation of the present invention will be explained.

In FIG. 2, the rotation speed of the motor value υ measured by the rotation speed detector and the motor current measured by the current detection device are input to the droop rate calculation device.

Therefore, when calculating the drooping rate d using the drooping rate calculation device, if the relationship shown in Fig. 4 is selected, the drooping rate will be small in the low speed range, and the speed reference value will be zero due to the speed correction signal of ξ. The problem that the electric motor stops rotating due to the following conditions will no longer occur.

Hereinafter, the speed drooping rate d calculated by the drooping rate calculating device will be specifically described with reference to FIGS. 8 and 4.

First, the rotation speed of the electric motor detected by the rotation speed detector is assumed to be in one direction, that is, to take a positive value, and this rotation speed Nb is the oxbs axis (however, Nm is the rated value N of the rotation speed N).
This is a small value of about several percent or less compared to o. ), and when one rotational speed Nb leaks Na, d=do
・・・・・・・・・Google it as 0 type. In this way, if the speed droop rate d is calculated by the droop rate calculation device, the fourth
The desired velocity droop rate as shown in the figure is obtained.

゛Again. speed reference signal Na given to the speed controller;
l! ! If the current of the motor - is I and the rotational speed of the motor 11+1 is Nb, then the following formula holds true according to the definition explained in FIG.

■Nb-Na-d-No.--0 Formula where Io represents the rated load current of the motor 151J, and No represents the rated rotational speed of the motor 15].

From (1), (2), and (0), the following (0) and (0) formulas hold true.

When Gb≦Emperor ■ Nb= Na -do-No・-・・・・・・・・・0
In addition, each Nb in the formula (■) and the formula (0) is.

When the speed command Na is the value of the following formula, it becomes the same value, and as the value of Na increases, the formula is switched from formula ① to formula 0.

Na= Nm 10 do-No・”－・・・・・・・・・
In other words, the drooping rate calculation device (2) calculates the drooping rate d defined by the formula 0 or the formula 0 corresponding to the rotational speed Nb of the electric motor I5n detected by the rotational speed detector (2), and It uses the current I of the motor Ill detected by the current detection device to generate a signal called d-No.....0 and outputs it to the speed controller. .

■According to the equation, the rotational speed Nb of the electric motor υ
does not become zero, and the defect of the conventional device in which the motor stops rotating due to the starting current or load current at startup is eliminated.

In the above embodiment, the rotational speed signal and the current signal input to the droop rate calculation device are respectively the values measured for the actual bottle, but it is also possible to use the reference signal given to the speed control device instead. good.

Further, in the above embodiment, the relationship shown in FIG. 4 was established between the rotational speed lfN and the droop rate d, but since these relationships change depending on the type of machinery and equipment and the operating method, any relationship that is suitable for them may be established. You can choose.

Furthermore, if the reason why the motor does not rotate in the low speed range is that the load current temporarily increases due to a stumbling block during startup, and the correction factor increases, once the motor starts, the load current decreases.

Therefore, instead of changing the drooping rate depending on the rotational speed, the problem can be solved by setting the drooping rate to zero until the completion of startup is detected, and then setting the drooping rate to the conventional drooping rate after the completion of startup.

Further, by setting the start-up droop rate to zero and changing the droop rate d depending on the motor rotation speed, operation in a low speed range can be more reliably performed.

Furthermore, although the embodiment has been described assuming that the motor is speed-controlled, the motor voltage may be used instead of the rotational speed even if the motor is voltage-controlled.

In addition, although the conventional equipment was explained using a two-stand rolling mill, it can also be applied to equipment that has multiple drive systems connected by materials, that is, equipment that is conventionally controlled with drooping characteristics. It can be applied to all cases.

As described above, according to the present invention, by changing the drooping rate depending on the motor rotation speed, drooping characteristics can be provided without stopping the motor in a low speed region.

Furthermore, by using a startup detection device, it is possible to eliminate the situation where startup is not possible due to material getting stuck during startup.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing a rolling mill with two stands;
Fig. 8 is a characteristic diagram showing the relationship between the motor speed I and the electric rotation train of a conventional device, Fig. 8 is a control configuration diagram of the motor showing an embodiment of the present invention, and Fig. 4 is a drooping diagram according to an embodiment of the present invention. quantity d
FIG. 3 is a characteristic diagram showing the relationship between the motor rotation speed N and the motor rotation speed N. 11)...Rolled material, Qυ, (2), (Foundation), (A)
...Roll, Q3゜(2)...Reducer, 04. Kanji・
...Wl motor, 51...Vt motor 52...power supply device, 68...speed controller, 54...rotation speed detector. 65... Drooping rate calculation device In each figure, the same reference numerals indicate the same or corresponding parts. Agent Makoto Kuzuno - Figure 1 Figure 2 Io 1-rated stuttering

Claims (1)

[Claims] a detector for detecting that the controlled electric motor is in a low speed region; a drooping rate calculation device for calculating a speed drop rate of the electric motor; and a speed control of the electric motor in accordance with the speed drop rate calculated by the droop rate calculation device. A motor control device comprising a speed controller, wherein when the detector detects that the motor is in a low speed region, the speed droop rate calculated by the droop rate calculation device is kept low.