SU1325651A1 - Device for controlling three-phase induction electric motor - Google Patents

Abstract

The invention relates to electrical engineering and is intended for use of 5 D / S 22 J5 and 8 8: D-D in unregulated reversible AC drives with a slowly varying load. The purpose of the invention is to increase the reliability of the device by reducing current surges. With the start of the phase-wise start of the electric motor and before the set of the nominal rotational speed determined by the trigger threshold of the comparator 20, the output of the multiplexer 19 is set to 1. Then the element 14 also sets 1, and the output of the element IS-NOT 13 is O. 6 and 7, 1 and O respectively appear. Optocoupler switch 10 is opened and switch 3 connects the motor windings according to the Star, 1 Il scheme. 3if S i СЛ С сою СЛ о СП

Description

The invention relates to electrical engineering and can be used in unregulated reversible AC drives with a slowly varying load.

The purpose of the invention is to increase the reliability of the device by reducing current surges.

The drawing shows a functional diagram of the proposed device for controlling a three-phase asynchronous electric motor.

The device contains a reversing starter 1 with a control unit 2, a switch 3 switching windings 4 of the stator C of the Triangle to the Star and vice versa, load sensor 5, one of the inputs of the first and second connectors 6 and 7 are connected to the outputs of the first and second delay elements 8 and 9, And the outputs of the first and second elements AND 6 and 7 through the corresponding optocouplers 10 and 11 are connected to the switch 3 switching the stator windings from the Triangle to the Star and vice versa, the inputs of the first element IS-NOT 12 are connected respectively to the outputs of the first and second e Delay 8 and 9, and the output of the first element AND-NO 12 is connected to the second inputs of the first and second elements AND 6 and 7, the first input of the second element AND-HE 13 is connected to the output of the third element 14, and the other input of the second element AND- NO 13 is connected to the first input of the third element AND 14 and the input of the third element 15 of the delay, the output of which is connected to the second input. the third element and 14.

The inputs of the first, second and third comparators 16-18 are combined and connected to the output of the load sensor 5, and the outputs of these comparators are connected respectively to the three address inputs of the multiplexer 19, whose information input is connected to the output of the fourth comparator 20 whose input is connected to the output of the slip sensor 21 , the output of the multiplexer 19 is connected to the input of the fourth delay element 22, the output of which is connected to the input of the third delay element 15, the output of the second element IS-HE 13 is connected to the input of the second element 9 behind the core The output of the third element And 14 is connected to the input of the first delay element 8.

In addition, the control unit 2 can be configured so that each triac reversing1 of the actuator i is controlled through its optocoupler key 23-27, the control inputs of the optocoupler keys are connected to the outputs from the first to the fifth element OR-28- 32 respectively, one of the inputs

the first and fourth elements OR- NOT 28 and 31 are combined and connected to the output of the first zero-body 33, to the input of which the signal of the linear voltage sensor 34 is supplied, one

from the inputs of the second and third elements OR-NOT 29 and 30 are combined and connected to the output of the second null organ 35, to the input of which a signal is sent from the sensor 36 of a linear voltage the first input of the transducer of the element OR NOT 32 is connected to the second stage of the third null organ 37, to the input of which a signal is supplied from the linear voltage sensor 38, the second input of the first element OR NOT 32 is connected to the output of the fourth element AND 39, the first input of which is connected to the second inputs of the first and second elements OR –YE 28 and 29, s exit third

the element AND-NOT 40 and one of the inputs of the fourth element AND-NOT 41, the second input of the fourth element AND 39 is sub-1O1; the output of the fifth element AND-NOT 42 to the second inputs of the third and

fourth element OR NOT 30 and 31

.

And to one of the inputs of the sixth element AND-NO 43, the other input of the sixth element AND-NO 43 is connected to the second input of the third element AND-NO 40 and

the start-back output of the command node 44, the start-forward output of the command node 44 is connected to the second inputs of the fourth and fifth elements AND-HE 41 and 42, the first one

element AND-NOT 42 and the third input of the third element 40 are combined and connected to the output. Stop of the command node 44, the first input of the third element AND-NOT 40 is connected to the output.

the fourth element AND-NO 41, the output of the sixth element AND-NO 43 is connected to the third input of the fifth element AND-NO 42,

The device works as follows

In the initial state, at all inputs of the fourth and sixth elements AND-NO 4 and 43 there is a logical correspondingly at the outputs of the third and fifth elements AND-HE 40 and 42, as well as the fourth element And 39, logical 1 is also present. Thus, on one Logical 1 is present from the inputs of all of the OR-NOT 28-32 elements, while the other inputs of these elements are supplied with the outputs of the corresponding null organs 33,35 and 37. As a result, the outputs of all the OR-NOT 28-32 elements present a logical O, optocoupler key 23-27 closed, control signals on these There are no electric motor de-energized.

When applying, for example, the Start-Forward signal from the command node 44, the output of the element AND-NO 40, and therefore the inputs of the elements OR-NO 28 and 29, the logical output O is set at the output of the element 39, At the same time, the other inputs of the elements OR-NOT 28, 29 and 32 pulses come from the outputs of the corresponding zero-organs 33.35 and 37 and at the moment when the voltage of this phase passes the load through zero to a positive half-wave, the pulses form at the outputs of the OR-HE elements 28 29 and 32, opening corresponding optocoupler keys 23,24 and 27. Zero-organs 33,35 and 37 are built so azom that is taken into account the order of phase rotation the mains supply, ie zero-bodies fix only the transition of the supply voltage curve from zero to a positive half-wave. In this case, when turning on the stator windings, ngshrimer, c. The triangle for a time equal to the sixth part of the period, the motor, although operating in a half-phase mode, however, excludes the possibility of the opposite rotation of its rotor

Dp stopping the motor, a Stop signal is sent from the comaid node 44 to the combined inputs of the elements AND-NO 40 and 42.

The switching of the windings of an electric motor according to the Star or Triangle schemes is carried out as follows.

At the initial moment, the electric motor is de-energized, then at the output of the comparator 20, and therefore at the information input of the multiplexer 19, there is a logical one. With the start of the phase-by-phase electrical start

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Before the nominal rotation frequency determined by the trigger threshold of the comparator 20, the output of the control of the multiplexer 19 is set to 1. Then the output of the element 14 also sets 1, and the output of the element IS-NOT 13 is O, resulting in elements 6 and 7 appears, respectively, I and O. The optocoupler switch 10 is opened and switch 3 connects the motor windings according to the Star circuit. Such a circuit, as is known, limits the starting currents and provides improved energy characteristics of the electric motor when idling or reduced loads of the drive mechanism.

With a set of rotational speed of the motor shaft close to the nominal output of the comparator 20, a logical O is established, i.e. the motor start phase is completed and the circuit goes into automatic load tracking mode of the motor.

When the motor is operating, the load voltage from the load sensor 5 is removed, proportional to the load of the motor, and fed to the inputs of the three ISIS comparators. Thus, the input voltage is converted into a proportional number, which is fed to the address inputs of the multiplexer 19. The multiplexer 19, in turn, selects and sends to the output from the information input corresponding to the specified address, the stored value - O.

The value of logical 1 at the information input and at the output of multiplexer 19 corresponds to the operation of an electric motor according to the Star circuit, logical O - to the Triangle scheme

In the case where the download; the motor is such that it is necessary to turn on the stator winding according to the Triangle scheme, a logical O is set up at the output of the delay element 22. Then, O 14 appears at the output of the AND 14 element, and logical 1 turns out at the output of the IS-NOT 13 element. 8 to the input element AND 6, which leads to an immediate shutdown of the switch 3. Logical 1 from the output of the element IS-NOT 13

with a time delay carried out by the delay element 9, it is necessary, the complete switching off of the triacs of switch 3, is fed to the input of the element And 7, which leads to the switching on of the optocoupler switch 11 and the corresponding switching on of the switch 3 according to the Triangle scheme.

At the moments of switching current surges may occur, as a result, a short logic о signal appears at the output of multiplexer 19, which can cause a false switching of the motor winding to the Triangle circuit. To eliminate these short-term triggers, delay element 22 is introduced, which delays the time of occurrence of the signal O,

To offset the random load conditions and, as a consequence, the appearance of a logical 3 signal at the output of delay element 22, a delay element 1J is provided. The occurrence of a logical 1 at the output of the AND 14 element is possible only after the expiration of the time delay of the delay element 15 and can be 5 - iOO s.

The IS-NO 12 element monitors the signals at the outputs of the delay elements 8 and 9 and in the case of simultaneous occurrence, which will lead to a short circuit, O is set at its output, the locking elements 6 and 7 and, as a result, the switch 3.

The device for controlling a three-phase asynchronous electric motor makes it possible to make extensive use of its reversible electric drive for responsible mechanisms, in particular escalators, thus providing enhanced energy characteristics of lightly loaded electric motors.

Claims (1)

Invention Formula Device for controlling three-phase asynchronous electric motor  containing a reversing starter with a control unit, which switches the cxaiopa windings from the Trigger cable to the Z drive and vice versa, load sensing, three delay elements, three AND elements, two NAND elements, one input of the first and second elements MeiiTOB I connected to the outputs of the first and second delay elements, and the outputs of the first and second elements I are connected via an appropriate switch; the optocouplers are connected to the switch for switching stator windings from the Triangle to the Star and vice versa, the inputs of the first element AND are NOT connected respectively to the outputs first and in second delay elements, and the output of the first element AND-NOT connected to the second inputs of the first and second elements AND, the first input of the second element AND-NOT connected to the output of the third element AND, and the other input of the second element AND-NOT connected to the first input of the third element AND and the input of the third delay element, the output of which is connected to the second input of the third element I, which is so that, in order to increase reliability by reducing current surges, four comparators are introduced into it, a multiplexer with three address and one information these inputs, the fourth delay element and the motor slip sensor, the inputs of the first, second and third comparators are combined and connected to the output of the load sensor, and the outputs of these comparators are connected respectively to the three address inputs of the multiplexer, whose information input is connected to the output of the fourth comparator, the input connected to the output of the slip date, the output of the multiplexer is connected to the input of the fourth delay element, the output of which is connected to the input of the third delay element, output v cerned element is connected to the input of the second delay element, a third element connected to output of AND with the input of the first delay element.