SU1267574A1 - Device for controlling d.c.elecric motor - Google Patents

Abstract

The invention relates to electrical engineering and can be used in pulsed speed control devices. Improving speed and efficiency is provided by the introduction of the sensor I2-back electromotive force of the electric motor 9, two threshold elements 13 and 14, as well as two logic elements AND 15 and 16. At the same time, the inputs of the threshold elements 13 and 14 are connected to the output of the sensor 12 back emf, and the outputs through the first inputs of the logic elements And 15 and 16 are connected to the inputs of the sistor switches 3 and 4, to the inputs of the transistor switches 1 and 2. Directly, and the keys 3 and 4 through the second inputs of the logical elements I I 5 and 16 are connected output of current limiting unit 11.2 Il. With O5 SD HJ

Description

The invention relates to electrical engineering and can be used in pulse devices for regulating the speed of direct current electric motors.

The aim of the invention is to increase the efficiency and speed of the device.

FIG. 1 shows a device diagram; in fig. 2 and 3 - diagrams of the motor current.

The device (Fig. I) for controlling a DC motor contains a power amplifier, assembled on four transistor keys IA, shunted by reverse diodes 5-8 and connected via a bridge circuit, to the same diagonal of which the 9th motor is connected, and another power supply 10, as well as a current limiting unit 11,

Sensor 12 of the electric motor's anti-electromotive force is entered into the device, two threshold elements 13 and 14 and two logical elements I 15 and 16 "At the same time, the inputs of threshold elements I3 and 14 are connected to the output of the sensor 12 of the electric motor's anti-electromotive force, and 15 and 16, the second inputs of which are connected to the output 1 of the current limiting unit 11.

The outputs of the logic elements 15 and 16 are connected to the inputs of transistor switches 3 and 4 connected to the first pole of the power source 10, the inputs of transistor switches 1 and 2 connected to the other pole of the power source 10 are connected to the output of the rod restriction block 11

The device works as follows.

When the motor is accelerated by a signal coming from a pulse-width modulator (for simplicity, not shown in Fig. 1), for example, switches 1 and 4 "Current" and motor counter-electromotive force rise in accordance with the equations

 and - iR CgW

(2)

- M,

where and

- for example mi e

nutrition enhance:

R is the resistance of the electric motor core;

L is the inductance of the core; I - the moment of inertia on the motor shaft;

C., C - respectively, the coefficients of anti-electromotive force and torque of the electric motor;

Mz - the moment of load on the motor shaft; i is the current of the core; co - rotational speed The current builds up exponentially (Fig. 2). When the current reaches a certain value, the current limit unit 11 is activated and gives a signal to close the keys 1 and 2. The key 1 closes and the current of the motor 9, supported by its self-induced EMF, flows key A and diode 7, decreasing in accordance with the equation

T. (3)

iR - Cgco

dt

unlike the known device. The current does not close through the power source, and therefore it will decrease at a slower speed, therefore, the ripple current will be less, which means that the current at the beginning of the next switching on of the key 1 will be higher than the known device. After the next switching on of the key 1, the processes are repeated, with the tendency to decrease in the rate of change of current at the moments of its increase. After reversing (Fig. 3), the current at high speed changes the sign to the opposite and when the current limiting value is reached, the current-limiting block 11 delivers the W-close signal to the key 2 and the logical elements 15 and 16. In the further operation of the circuit depends on how much speed the motor has managed to brake before that moment.

Consider the case when the speed corresponds to counter electromotive force E g With this polarity, the back electromotive force (left - plus) is triggered when E - then the threshold element 13, which supplies the closing signal to the logical element 15, the latter closes key 3, since its second the input already has a signal of the current limit unit 11 (threshold element 14 gives a closing signal at E RI, but of a different polarity). If key 3 is not closed, as key 4 was not closed during acceleration, the current of the core over the action of the back emf would continue to increase to a value greater than 1 (since Е Е1, ") As soon as the engine speed drops to a value at which ЕiRIfo, the creaking signal at the output of the threshold element 13 will disappear (time t, in Fig. 3), After the current limiting block triggers, only key 2 closes, and key 3 remains open, the Current, decreasing, flows through key 3 and diode 8. And will decrease in accordance with equation (3). In the future, the processes of current change will be similar to what happens during acceleration, i.e. with less pulsations. Reducing pulsations while maintaining the institute's maximum current I-ro (limited by the modality of the keys used) leads to an increase in the speed of the drive and an increase in the efficiency of the device. 1 4 more Formulas Device for controlling a DC motor, containing a power amplifier, assembled on four transistor switches, shunted by reverse diodes, and included in a bridge circuit, to one di-. The agonal of which is connected to the motor motor, and to the other - the power source, as well as the current limiting unit, which is different in that, in order to increase efficiency and speed, a date is entered into it. A counter electric motor, two threshold elements and two logical elements. And, the inputs of the threshold elements are connected to the output of the counter-EMF sensor, and the outputs with the first inputs of the corresponding logic elements And, the second inputs of which are connected to the output of the current limiting unit, and the outputs with inputs transistor switches connected to the first pole of the power source; the inputs of transistor switches connected to the second pole of the power source are connected to the output of the current limiting unit.

Claims (1)

Claim A device for controlling a DC motor containing a power amplifier, assembled on four transistor switches, shunted by reverse diodes, and connected in a bridge circuit, to one di-axis of which the motor armature is connected, and to the other a power source, as well as a current limiting unit, characterized in that, in order to increase the efficiency and speed, date- entered into it. chik counter-EMF of the electric motor, two threshold elements and two logical ones. element, And, the inputs of the threshold elements are connected to the output of the counter-emf sensor, and the outputs are the first inputs of the corresponding logical elements AND, the second inputs of which are connected to the output of the current limiting unit, and the outputs with the inputs of transistor switches connected to the first pole of the power supply, the inputs of transistor The keys connected to the second pole of the power supply are connected to the output of the current limiting unit.