SU1577042A1 - Device for dynamic braking of electric motor - Google Patents

Abstract

The invention relates to electrical engineering and can be used in electric drives of various mechanisms for automatic braking of electric motors. The aim of the invention is to reduce the braking time. By introducing into the device a switching unit 6, a low-pass filter 7, an amplifier 8 and using them together with the coding block 1, trigger 3, counter 4, pulse generator 5 and key element 2, it produces a braking signal proportional to the frequency of rotation of the motor. In this case, the initial deceleration current is set at the level of the maximum possible, which makes it possible to reduce the deceleration time and the stick out angle of the electric motor compared to the prototype. 3 il.

Description

1

The invention relates to electrical engineering and can be used in electric drives of various mechanisms for automatic braking of electric motors,

The aim of the invention is to reduce the braking time.

Fig, 1 shows a block diagram of the device; 2 and 3 are timing diagrams explaining its operation.

The device for dynamic braking by an electric motor contains a coding unit 1, a controlled key element 2, a trigger 3, a counter 4, a pulse generator 5, a switching unit 6, a low-pass filter 7 and an amplifier 8. The input of the coding unit 1 is mechanically connected to the motor shaft 9 and the output of the coding unit 1 is connected to the installation input of the trigger 3. The trigger output, 3 is connected to the first input of the switching unit 6 and to the installation input of the counter 4, the output and counting input of which are connected respectively to the reset input of the trigger 3 w out home generator 5 pulses. The output of the switching unit 6 through the low-pass filter 7, the controlled key element 2 and the amplifier 8 is connected to a terminal for connecting an electric motor, and the second input of the switching unit 6 is intended to be connected to a reference voltage source

The device works as follows.

The operation of the device is based on the formation of a braking signal, which is proportional to the speed of rotation of the engine, thereby providing a quick and smooth deceleration of the engine (Fig. 2). When the engine 9 is rotated, the coding unit 1 kinematically associated with it continuously displays information about the angular position of the engine shaft 9 or a sequence of pulses at a frequency multiple of the engine rotational speed. In any case, at the output of the coding unit 1, a sequence of pulses can be distinguished, the period of which is inversely proportional to the speed of rotation of the engine (Fig. 3a). On the first positive edge of the pulse of the coding unit 1, the trigger 3 is set to 1, which is fed to the installation input of the counter 4 and thereby enables the high frequency clock counts arriving at its counting input from the output of the generator 5 pulses. When a predetermined number of pulses, determined by the volume of counter 4, arrives, a pulse is formed at the output of the latter (Fig. 3b), which translates trigger 3 into O, and the counting stops. When the next pulse arrives from the output of the coding block, 1 cycle is repeated. As a result, the output of the trigger 3 generates a signal (Fig. 3b), in the form of a sequence of pulses of constant duration, the frequency and duty cycle of which is proportional to the speed of rotation of the output shaft of the engine 9. In the switching unit 6, the intervals of the pulse sequence from the trigger output 3 to zero level (fig.Zg). The low pass filter 7 extracts the average.

the voltage value of a sequence of pulses of constant duration (Fig. 3D) is proportional to the rotational speed of the engine 9. When the braking operation is not set (level.log, O to

the control input of the device — the control input of the key element 2), the key element 2 is in the open state. If there is 1 at the control input of the device, the key element 2 skips

the signal from the output of the low-pass filter 7 to the input of the amplifier 8, which amplifies the reversing deceleration signal and converts it into the form necessary for effective control of the motor 9.

The smoothness of braking is achieved due to the presence of an aperiodic link (low-pass filter 7) in the circuit producing the engine braking signal 9. The braking signal is then

,

(one)

where y is the duty cycle of the output pulses from the output of the switching unit;

Uo is the voltage of the external voltage source; n is the volume of the counter;

t is the period of pulses following the generator output;

T is the period of the pulses following the output of the coding block.

Thus, in the device, the braking is performed by a reverse voltage directly proportional to the engine rotational speed 1 / T, which has a maximum value at the initial moment of time, then it decreases in proportion to the rotational speed of the engine to zero (at the moment of a complete stop of the engine) . The efficiency of the device is determined by the volume counter and the pulse frequency 1 / t from the generator output 5 pulses, as follows from (1), as well as the voltage UQ of the external reference source,

This device allows to reduce the motor deceleration time in comparison with the prototype by increasing the initial braking torque, the value of which is selected at the level of the maximum possible and is not limited by the speed of the control circuit elements. An additional advantage of the device is the reduction of the stick out angle of the engine, which can be significant for particular applications, for example, in the drive of magnetic recording equipment, etc.

Claims (1)

Apparatus of the Invention A device for dynamically braking an electric motor comprising an encoding unit for mounting on a shaft. electric motor, controlled key element, trigger, the output of which is connected fc to the installation input of the counter, the counting input of which is connected to the output of the pulse generator, characterized in that, in order to reduce the deceleration time, a switching unit, a low-pass filter and an amplifier, an output are introduced into it which is connected to the terminals for connecting the electric motor, the output of the coding block is connected to the input of the trigger, the reset input of which is connected to the output of the counter, the output of the trigger is connected to the first input ayuschego unit, the second input of which is intended for connecting the x source reference voltage, the output of the switching unit via the low pass filter and controlled by a key element connected to the input of the amplifier.