SU1457138A1 - Monitoring device for reversing of excitation current of d.c. motor - Google Patents

Abstract

This invention relates to electrical engineering and can be used in direct current drives. The aim of the invention is to increase reliability. The device contains an amplifier-limiter 2 connected between the excitation current sensor 1 and the differential link 3. The output of the excitation current sensor 1 through the second threshold element 5 is connected to the coincidence element 6. When the excitation current of the electric motor is changed at the maximum speed in the control zone, the device blocks the drive off. The device provides control of the reverse floor both when the engine is stopped and when the reverse is braking the floor. 2 Il. WITH/)

Description

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This invention relates to electrical engineering and can be used in direct current drives.

The aim of the invention is to increase reliability.

Figure 1 shows the control device; figure 2 - timing charts of the device - the output signals of the blocks.

The control device for reversing the excitation current of the DC motor comprises a current sensor 1 and a series-connected limiting amplifier 2, a differentiating element 3 and the first threshold element 4, the second threshold element 5, the input of which is connected to the output of current sensor 1 and the amplifier input - limiter 2, a coincidence element 6 whose inputs are connected to the outputs of the corresponding threshold elements 4 and 5, and the output is the output of the device.

The control device when the reverse current of the engine is as follows ..

When the excitation current changes to the opposite polarity with a maximum speed, which is determined by the supply voltage of the winding and its inductance, the output of current sensor 1 is a signal, the voltage of which corresponds to the form of this change (Fig. 2).

This signal is fed to the input of the amplifier-limiter 2 and the input of the threshold element 5.

With the passage of current values ± Ig. On which the protection from a broken field is tuned, at the inverting output of the threshold element 5 a logical signal 1 .. (Fig. 6) appears, which is fed to one input of the coincidence element 6.

The signal passing through limiting amplifier 2 is amplified in K times, where Kus is the gain of the amplifier, calculated by the formula.

K US -.- K tnin

where UOP is the limiting voltage; and - current sensor output at

Bmin

Bm; ii

, - safety factor

In this case, the device does not respond to changes in current that are higher. TO,.

With the passage of current zone 1c ";" K: at the output of amplifier 2, a signal appears proportional to the change in current, and this change (n) from the output in K at

Have

time pain

R

0

five

five

more than at the entrance (fig.Z)

This change is highlighted by differentiating element 3 (Fig. 4) and is fed to the input of threshold element 4, at the inverting output of which logical O appears. It prohibits the passage of logical 1 from second threshold element 5 through coincidence element 6.

As a result of the addition of the signals at the output of the elements 6, a logical O is obtained, which permits the operation of the electric drive.

When the field is broken or the direction changes in zone 1c,; n, the derivative at the output of the differentiating link is zero, the output (Fig. 3) of the threshold element 4 appears logical 1. The addition of the logical 1 from the threshold element 4 (no change of the field from the maximum speed) from logic 1 threshold element 5 (excitation current is less than current of protection setpoint ± IB.) produces at the output of element 6 a match of logical I, which is the command to turn off the drive.

Thus, as long as there is a change in the excitation current of the electric motor at maximum speed in the control zone, the device blocks the tripping of the electric drive.

The device controls the breakage of the floor, as in this case the lock is released, the drive is turned off.

The device has a control zone for the excitation current, which allows it to be used for monitoring within the protection setpoint of the surge field.

Claims (1)

The device provides control of the reverse floor both when the engine is stopped and when the reverse is braking the floor. Invention Formula Control device for reverse motor current excitation 31A57I a direct current, containing a current sensor and a series-connected differentiating element and the first threshold element, distinguish it with the fact that, in order to increase reliability, an amplifier-limiter connected between H 38 the output of the current sensor and the input of the differentiating element, the second threshold element, the input of which is connected to the output of the current sensor, and the coincidence element, the inputs of which are connected to the outputs of the threshold elements, and the output is the output of the device.