SU1288880A1 - Control device for d.c.electric motor - Google Patents

Abstract

This invention relates to electrical engineering and can be used in direct current drives. Expansion of the field of application due to current limiting in the braking mode is provided by using two threshold elements 17, 18 with an asymmetric hysteresis loop i and a transistor control logic 2,3,4,5 of the bridge converter. The current limit is achieved in the start, deceleration and reverse modes with any rotational speed, 2 Il. W С

Description

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

The aim of the invention is to expand the scope by limiting the current in the braking mode.

Fig. 1 is a schematic of the device for controlling a direct current electric motor; 2, time diagrams of the device operation.

The device for controlling the electric motor 1 contains a bridge with transistors 2 5, the electric motor 1 is connected to one diagonal, and the power source, the first 6 and second 7 diodes, the first current sensor 8, and the trigger 9, the first 10 and the second are connected to the other. And, the second sensor-i 12 current, the third 13 and fourth 14 diodes, the third 15 and the fourth 16 schemes And, the outputs of which are connected to the bases of the third 4 and fourth 5 transistors, two threshold elements 17 and 18 with an asymmetric hysteresis loop, the outputs of which connected respectively to the first inputs of the ne howling 10 and second 11 And schemes, as well as the third 15 and Fourth 16 schemes And, four keys 19 - 22, the outputs of which are combined and connected to the inputs of threshold elements 17 and 18, two inverters 23 and 24 and two three-input OR-NOT circuits 25 and 26, with the sensors 8 and 12 currents made in the form of resistors and included in the emitter circuit, respectively, of the first 2 and second 3 transistors.

The outputs of the sensors 8 and 12 currents are connected with the inputs of the first switch 19 and the first inverter 23 and with the inputs of the second switch 20 and the second inverter 24, the outputs of the inverters are connected to the inputs of the third 2 and the fourth 22, respectively, the control input of the first 19 switch is connected to per. the primary inputs of the OR-NOT circuits 25 and 26 and the base of the first 2 transistors, the control input of the second switch is connected to the second inputs of the OR-NOT circuits 25 and 26 and the base of the second 3 transistors, the outputs of the first. 25 and second 26 OR-NOT circuits with control inputs of the third 21 and fourth 22 keys, respectively, the direct output of the trigger 9 is connected to the third input of the first 25 OR-NK circuits and to the second input

five

I will give the first 10 and fourth 16 AND circuits, the inverse output of the trigger is connected to the third input of the second 26 OR-NOT circuit and to the second inputs of the second 1I

and the third And 15, diodes 6, 7, 13 and 4 are connected between the emitters and the collectors of the respective transistors 2-5 of opposite polarity of the power supply.

The combination of the keys 19–22 of the inverters 23 and 24 and the OR-HE schemes 25 and 26 ensures the formation of a continuous signal at the inputs of the threshold elements proportional to the current of the electric motor 1.

The device works as follows.

Suppose that a single signal Ug, is fed to the input S of trigger 9. According to the input signal S, the flip-flop 9 is set to a single state on the forward output, the Single SI1

From the direct output of the trigger enters the second inputs of logic circuits AND 10 and 16, the first inputs of all four logic circuits AND 10, 11, 15 and 16 receive single signals from the outputs of the threshold elements 17 and 18. As a result, the outputs of logic circuits

Both 10 and 16 there are single signals that bring transistors 2 and 5 to the open state. Except that-. first, a single signal from the output of the circuit AND 10 closes the high-speed

5, the key 19 and, through it, the output of the resistive current sensor 8 is connected to the common input of the threshold elements 17 | 18. The zero signal at the common input of the threshold elements corresponds to

0 the absence of current in the power circuit of the device. Therefore, the threshold elements retain the accepted single state of the output. I

g When powering the n-and transistor bridge in the power circuit through the open transistor 5, the motor 1, the transistor 2 and the current sensor 8 begins to flow current, increasing

Q value. In proportion to the current of the electric motor 1, the signal at the output of the current sensor 8 increases and, accordingly, the signal at the common input of the threshold elements 7 and 18 which have

unequal response thresholds. The trigger threshold of the element 17 is the threshold of the triggering of the element 8 by the amount of half the hysteresis loop of the element 18.

When the current reaches the operation threshold of the threshold element 17 (time t, in FIG. 3), the latter switches to the zero state of the output. In accordance with the zero signal of the threshold element 7, a zero signal appears at the output of circuit 16 and the transistor 5 closes. The motor current closes across the circuit of the transistor 2, current sensors 8 and 12, and diode 7. When the current decreases to the switching on level of the threshold element 17 (time tj to vig.3), the latter switches to the output unit and, in turn, translates transistor 5 v Access the state, in the further process .raboty device is periodically repeated in the described sequence. A current at the core winding is limited at a given level by the switching thresholds of the threshold element, which are determined by the width of the hysteresis loop (Fig. 2). When reaching the steady-state frequency of rotation, the current in the root winding decreases to a value less than the thresholds of the element 17 (time t Fig. 3), and the device assumes an initial state in which transistors 2 and 5 are open.

For reversing or braking the motor, it is necessary to remove a single signal and send a signal Ug, (to the R input of the trigger 9. According to the input signals, the RS flip-flop is set to one state on the inverse output and to the zero state on the forward. Accordingly, with the trigger switching Zero signals appear at the outputs of the AND 10 and 16 circuits and single signals at the outputs of the AND 11 and 15 circuits, since the first inputs of these elements receive single signals from the outputs of the threshold elements. Transistors 2 and 5 are closed, transistors 3 and 4 are opened , rum that is opened - the key 19 and the key 20 is closed.

At the time of locking the transistors 2 and 5, the motor current is closed through the reverse diodes 7 and 13 and the current sensor 12. In this case, the direction of the current is opposite to the polarity of the power source and against the EMF of the electric motor. The current decreases to zero (the time interval in Fig. 3), and then begins to increase sharply in this circuit in the forward direction through the open transistors 3 and 4. A signal proportional to the current is extracted on the 5 12 current sensor and from its output goes to common input threshold elements through a closed key 20.

When the current reaches the threshold value of the element -17 (time tg in FIG. 3), the latter switches to the zero state on the output. The zero signal from its output closes the transistor 4. From this point on, the current is closed along the circuit

5 through the open transistor 3, the sensors 8 and 12 of the current and the reverse diode 6. Under the action of the EMF in this circuit, the current continues to increase. When the current reaches the trigger setpoint of the threshold element 18 (time tj), the latter switches to the zero state on the output. The zero signal from the output of the element 18 of the transistor 3 is brought to the closed state.

 The current flows through the reverse diodes 6 and 14 and the current sensor 8. Simultaneously with the closing of the transistor 3, the switch 20 and the switch 21 are closed. At the moment of current reduction to the level of the threshold element 18 (tg in Fig. 3), the latter switches to the output one state. In accordance with the switching, the transistor 3 is opened, the switch 21 is opened and

5, the key 20 closes. Next, the operation of the device is repeated in the opi- sledding sequence.

Thus, the current of a rotating direct current motor (EPT) is limited in its braking interval. Under the action of current in the core winding EPT is intensely slowed down. By reducing

5, the rotation frequency to a value close to zero, the distance of the current under the action of the EMF is stopped, and its decrease occurs (time t, in FIG. 3). At the time when the current decreases to the trigger level of the threshold element 17 (time tj on 3) the latter switches to a single output state. Accordingly, the transistor 4 is opened. Through the open transistors 4 and 3 and the sensor 12, the current in the core winding will increase the current under the action of the voltage of the power supply.

The increase in current leads to the inclusion of the threshold element 17 in the zero state on the output, followed by locking of the transistor 4 and closing the current through the circuit: transistor 3, current sensors 8 and 12 and diode 6. The common input of the threshold elements receives a signal from the current sensor 12 through the open switch 2; Next, the switching processes of transistor 4 are periodically repeated. After some time, the motor stops, then starts to accelerate in the opposite direction. The process of limiting the current at this stage is similar to the described starting process.

When starting and braking the motor, it is necessary to remove the supply voltage from the transistor bridge at the moment the rotor stops, or reduce the current limit setting to zero.

The device provides the limitation of the electric motor current in all operating modes: during start, braking and reverse with any rotational speed.

Claims (1)

Invention Formula A device for controlling a direct current electric motor, containing a transistor bridge, to one di- 35 with control inputs of the respective of which is connected electrically to the third and fourth keys, the motor, and to the other - a source PI direct output of the trigger is connected to a cable the first and second diodes, the first to the third input of the first circuit current sensor, the trigger, the first and second and second inputs of the first and fourth rui circuit AND, the outputs of which are connected by the AND circuit, the inverse output of the trigger under the base of the first and second transistor keys to tre To the second input of the second circuit, the emitters associated with the negative output of the power source, the second inputs of the AND circuits are combined and connected with the trigger output, which is 45 and 45 with the aim of expanding the NOT and to the second inputs of the second and third circuits AND, the diodes are connected between emitters and collectors of corresponding power transistors with opposite polarity of the power supply. five 0 five 0 widening of the field of application due to current limiting in-deceleration mode, a second current sensor, a third and fourth diode, a third and a fourth AND circuit, the outputs of which are connected to the bases of the third and fourth transistors, two threshold elements with an asymmetric hysteresis loop, whose outputs connected respectively to the first inputs of the first and second circuits And and to the first-1 and inputs of the third and fourth circuits And, the four key outputs of which are combined and connected to the inputs of the threshold elements with asymmetric loop hysteresis, two inverters and two three-input OR-NOT circuits, with current sensors made in the form of resistors and connected to the emitter circuit of the first and second transistors, respectively, the outputs of the current sensors are connected respectively to the inputs of the first switch and the first inverter and to the inputs of the second switch and the second inverter , the inverter outputs are connected to the inputs of the third and fourth keys, respectively, the control input of the first key is connected to the first inputs of the OR NOT circuit and the base of the first transistor, the control input of the second key with one with the second inputs of the NOR circuit and the base of the second transistor, the first and second NOR circuits rsi connected with the control inputs of the third and fourth keys, respectively, the direct output of the trigger is connected to the third input of the first circuit and to the second inputs of the first and fourth circuits, And the inverse output of the sub trigger to the third input of the second circuit 1-1T1I-NOT and to the second inputs of the second and third circuits AND, diodes are connected between emitters and collectors of corresponding transistors of opposite polarity of the power source. i) FIG. Compiled by V. Trokhimenko Editor N. Egorova, Tehred I. Were Corrector A. Tsko Order 782Г / 57 Circulation 683 VNIIPI State Committee of the USSR for the inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab, 4/5 Production and printing company, Uzhgorod, st. Project, 4 Subscription