SU1676057A1 - Dc electrical drive - Google Patents

Abstract

The invention relates to electrical engineering and can be used to control three-phase asynchronous electric motors when powered from a single-phase network. The aim of the invention is to increase the braking efficiency. The goal is achieved by connecting the windings 2, 3 and 4 of the electric motor 1 according to the delta scheme, inserting the rotor rotation sensor 10 and the braking control unit into the control system 9. The device provides dynamic braking of the electric motor 1, parametric and frequency control in the motor mode, as well as shutdown of the electric motor 1 depending on the value of the reference signal. 3 il.

Description

The invention relates to electrical engineering and can be used to control three-phase asynchronous electric motors when powered from a single-phase network.

The aim of the invention is to increase the braking efficiency

FIG. 1 shows a structural diagram of the power section of the electric drive; in fig. 2 is a control system diagram; in fig. 3 - timing diagrams for the operation of the device.

The AC electric drive contains a three-phase asynchronous electric motor (ATD) 1 with optimal windings 2-4, a bridge semiconductor switch, made on four transistor switches 5-8 AC, control system 9 and rotor sensor 10. One diagonal bridge switch is connected to the terminals for connecting a single-phase power source, and to another

The switch diagonals connect the first terminals of the first 2 and second 3 stator windings of the electric motor 1, the first terminal of the third stator winding 4 of which is connected to one of the terminals for connecting a single-phase power source. The second terminals of the first 2 and second 3 stator windings are connected to the first terminals of the second 3 and third 4 windings, respectively. The inputs of the rotor rotation sensor 10 are connected respectively to the second output of the third winding 4 and the first output of the first winding 2 of the electric motor 1. The output of the rotor rotation sensor 10 is connected to the input of the control system 9, the outputs of which are connected to the control switches of the transistor switches 5-8 of the bridge switch.

The control system 9, (FIG. 2) consists of an input signal adjuster 11, an input signal polarity indicator 12, two blocks 13 and 14 of a phase shift, a block 15

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generating the absolute value of the input signal, power supply voltage indicator 16, three comparison blocks 17 and 19, input signal comparator 20, voltage-frequency converter 21, frequency control unit 22, operating mode switching unit 23, control pulse distribution unit 24, control and protection unit 25, braking control unit 26. The braking control unit 26 contains four two-input elements OR 27-30, four two-input elements AND 31-34, one two-input element AND-NOT 35 and one inverter 36. The first inputs of the three elements OR 27-29 and the AND element 31 form the first four inputs bpock 26 the braking control, the first input of the element OR 30 forms the fifth input of the braking control block 26, and the two inputs of the element AND 32 form the sixth and seventh inputs of the block 26. The output of the element 32 And is connected to the combined second inputs of elements 27-35 directly, and through an inverter 36 - to the united torym inputs of elements 30 and 31. The outputs of elements 27 and 35 are connected to the inputs of AND gate 34, whose output is the first output of the control unit 26 inhibition. The outputs of the elements 29 and 30 are connected to the inputs of the element AND 33, the output of which forms the third output of the braking control unit 26. The outputs of the elements OR 28 and AND 31 form the second and fourth outputs of the braking control unit 26, respectively. The control system 9 also includes a galvanic isolation and amplification control pulse block 37 and an input signal indicator 38. The inputs of the input polarity indicator 12 and the input absolute value forming unit 15 are combined and connected to an input signal setting device 11. The output of the input polarity indicator 12 is connected to the first input of the control pulse distribution unit 24. The output of the absolute value block 15 of the input signal is connected to the first inputs of three comparison blocks 17-19, the second inputs of which are connected to the outputs of the phase shifter 13, the input of which is connected to the input of the indicator of polarity supply 16 and serves to connect the alternating voltage wives The output of the voltage polarity indicator 16 is connected to the first input of the frequency control unit 22. The inputs of the three comparison blocks 17-19 are connected to the first three inputs of the operation mode switching unit 23. Outputs

The comparison blocks 17 and 19 are also connected to the fifth and sixth inputs of the frequency control unit 22. The inputs of the comparator input signal 20, the Converter 21

the voltage-frequency and the input signal indicator 38 are combined and connected to the output of the absolute value forming unit 15 of the input signal. The output of the comparator 20 of the input signal is connected to the fourth input of the operating mode switching unit 23. The output of the voltage-frequency converter 21 is connected to the input of the phase shift unit 14, three outputs of which are connected

to the second, third and fourth inputs of the frequency control unit 22, three outputs of which are connected to the fifth, sixth and seventh inputs of the operation mode switching unit 23, the first output of which

connected to the third input of the control and protection unit 25. The second and third outputs of the operation mode switching unit 23 are connected to the third and second inputs of the control pulse distribution unit 24,

the outputs of which are connected to the first and second inputs of the control and protection unit 25, the four outputs of which are connected to the first four inputs of the braking control unit 26, the fifth and

The sixth inputs of which are connected respectively to the outputs of the indicator 16 of the polarity of the supply voltage and the indicator 38 of the input signal, and the seventh input of the braking control unit 26 forms the input of the control system 9. Four outputs of the braking control unit 26 are connected to the inputs of the galvanic isolation and amplification unit of the control pulses 37, the outputs of which form the outputs

control systems 9.

The AC drive works as follows.

In the presence of the signal set UmO (intervals 0 ok ats and OA oi

in FIG. 3) the output of the input signal indicator 38 will contain a logical O signal, which is fed to the sixth input of the braking control unit 26. In this case, the outputs of element 32

there will be a signal O, at the outputs of elements 35,36 and 30 there will be a signal of logical 1, and the signals at the outputs of elements 27-30, 33 and 34 will be identical to the signals at their first inputs. Thus, at the outputs of the block

26, the braking control will have signals identical to those on the first four inputs of block 26, respectively, independently of the level of signals on the fifth and seventh inputs of block 26,

U26, U26, U26, U26. If there is an input signal of positive polarity exceeding the threshold voltage of block 20 (interval 0 tot CM at the output of block 12, a signal G is formed, and at the output of block 20 an O signal. At the same time, the frequency control channel is closed by the logical keys of the operating mode switch 23, and the parametric control channel is open. In this case, the signal 1 is continuously supplied to the first input of the control pulse distribution unit 24. At the outputs of the blocks 17-19, three square voltages with the same filling factor are formed and out of phase in accordance with the reference voltage generated by block 13, respectively, -tg / 6, -p 12 and JT / 6 relative to the supply voltage, 8 as a result of the operation of block 23, the indicated voltages appear at its three outputs. If signal 1 is present, the first input of block 24 will have its voltage at the second and third outputs of the block 2%, respectively. In block 25 four logical AC key control signals are generated, which are received through block 26 control braking and b galvanic isolation and amplification of control pulses to control inputs of the corresponding switches 7, 5, 8, and 6 (U26, I2b, U26IM, U2elv). The operation of the keys in accordance with the received control pulses ensures the formation of a three-phase system of output voltages, the values of which are controlled by the pulse-width modulation of the single-phase supply voltage.

When the polarity of the input signal changes (interval in FIG. 3), the output of the input signal indicator 12 generates a signal O, which, arriving at the first input of block 24, switches the passage channels of the key control switches of the semiconductor switch in such a way that the pulses received at the input of keys 7 and 6, will be received at the input of keys 5 and 8 and vice versa. This, in turn, will change the order of the output voltage phases.

If the input signal is reduced to a positive polarity to a value less than the threshold of block 20 (interval "1 u) t О2 in FIG. 3) the signal 1 is formed at the outputs of blocks 12 and 20. In this case, the parametric control channel is locked and the frequency control channel is open. (At the output of the voltage-frequency converter 21, there will be a signal whose frequency is proportional to

the absolute value of the input signal. At the output of the phase shift unit 14, three rectangular voltages are formed, out of phase with respect to each other by an angle of 2 liters / 3, which arrive at

the second, third and fourth inputs of the frequency control unit 22, to the first input of which information is received on the sign of the network voltage in the form of a voltage Uie. The fifth and sixth inputs of the block 22 are received

rectangular voltages from the outputs of blocks 17 and 19 with a predetermined fill factor that determines the values of the output voltage of the converter. Rectangular voltages from the outputs of block 22

after passing the blocks 23 and 24, they enter the block 25, where the key control pulses 5-8 are generated, the passage through the blocks 26 and 37. As a result of the keys 5-8 in the windings 2-4 of the ATD 1,

a three-phase system of adjustable in frequency and effective voltage (Fig. 3). When the polarity of the input signal changes in block 24, the switching channels of the key control pulses 5–8 switch, which ensures a change in the order of the phases of the output voltage. Thus, the voltages and currents in the phases of the windings 2-4 of the ATD 1 are determined by the circuit

phase connections - triangle Ua, Ua, 1) 4, 12. 1з, U in FIG. 3). At the same time, at intervals of 0 (Ut aiHO4 ft t oo, parametric control is carried out, and at the interval of ori wt 05 - frequency control. Under the influence of stresses 1) 2. Uz The LM in engine 1 develops a torque and the rotor rotates.

If now at some point in time, for example, O2 signal is set to Un

will be equal to zero, then the following changes will occur in the operation of the device. At the output of the indicator 38, the input signal sets the signal 1, which is fed to the sixth input of the braking control unit 26. The fifth input of the block 26 receives the signal Uie corresponding to the polarity of the supply voltage, and the seventh input of the block 26 receives the signal Uio from the rotor's rotation sensor 10. Because by the time

since t sc.2 in the winding 4 of the ADT 1 current c flows, then the output of sensor 10 will be signal 1. At the same time, the outputs of elements 32, 27, 28 and 29 will be signal 1, at the output of elements 36 and 31 - signal O, the outputs of the elements 30

and 33 there is a signal equal to the signal at the fifth input of block 26, i.e. the signal from the output of the indicator 16 of the polarity of the supply voltage U16, and at the outputs of the elements 35, 34 is the signal inverse from the signal at the fifth input of the block 26, i.e. Ui6. Thus, on the first output of block 26 there is a signal Die, on the second - signal 1, on the third

the signal Uie, on the fourth, the signal O, regardless of the state of the signals at the first four inputs of block 26, i.e., regardless of the operation of the rest of the control system 9. As a result of operation of the block 37, the key 5 is in the closed state and shunts the phase winding 4 in the motor 1, the key 6 is open, and the keys 8 and

7 are connected paraphase depending on the sign of the alternating supply voltage Un. This will provide a half-wave rectification of the supply voltage applied to the windings 3 and 2 of the ATD 1, respectively, of positive and negative polarity, which will ensure the flow of currents of the same sign in each of these windings. Dynamic braking occurs in the engine, the intensity of which is ensured by the high level of rectified current.

During braking, the speed of rotation of the rotor is reduced. When the rotor stops at a certain moment (O t 03 the output signal of the rotor's rotation sensor 10 Uio is O. This signal goes to the seventh input of the braking control unit 26. The operation of the unit 26 is similar to that discussed above when, i.e. the outputs of block 26 are equal to the signals at the first four inputs of the block, respectively, regardless of the level of the signals at the fifth and sixth inputs.With a zero input signal, the output of blocks 12 and 15 produces a signal O, and at the output of block 20

-signal 1. In this case, the parametric control channel is closed by logical keys in the operation mode switching unit 23, and the frequency control channel is open. At the outputs of blocks 17-19, three voltages are obtained with a fill factor of one. The voltages from the outputs of blocks 17 and 19 are fed to the fifth and sixth inputs of frequency control unit 22. Regardless of the signals at the remaining inputs of this block, its three outputs will have signals 1. Similar signals are formed at the outputs of blocks 23 and 24,

In block 8, signals will be generated which, having passed through blocks 26 and 37, ensure the inclusion of keys 5 and 7 and the locking of keys 6 and 8 after the rotor ATD1 has stopped.

At the same time the phase windings 2-4 ATD 1

short-circuited and disconnected from the power source. Thus, with a zero reference signal Un 0 and a zero speed of rotation of the rotor ni 0, the engine braking process ends and

disconnects from the power source. During a pause, the "power supply" does not consume electrical energy from the power source.

The proposed device allows ADT to be transferred to the effective dynamic braking mode when the input signal reaches a zero value and is then automatically disconnected from the power source when the rotor is completely stopped. In the proposed device saved all the functionality and properties inherent in the known device. An increase in the braking efficiency of the ATD is achieved without changing the power section of the device, the semiconductor switch, and, therefore, with practically the same weight and size indicators.

Claims (1)

Invention Formula AC drive containing asynchronous three-phase electric motor, bridge semiconductor switch, made on four transistor switches of alternating current, one the diagonal of the bridge switch is connected to the terminals for connecting a single-phase supply voltage to the source, and the first terminals of the first and the first are connected to the other diagonal of the bridge switch the second stator windings of the asynchronous electric motor, the first output of the third stator winding of which is connected to one of the terminals for connecting a single-phase supply voltage to the source, a control system including an input signal setter, an input signal indicator, two phase shift units, an absolute generating unit input signal values power supply polarity indicator, three comparison units, input comparator, voltage-frequency converter, frequency control unit, operating mode switching unit, control pulse distribution unit, control and protection unit, galvanic isolation and amplification of control pulses, inputs of the input signal polarity indicator and the input signal absolute value generating unit are combined and connected to the output setpoint of the input signal, the output indicator of the input signal is connected to the first the input of the control pulse distribution unit; the output of the absolute value block of the input signal is connected to the first inputs of the three comparison units; the second inputs which are connected to the outputs of the first phase shift unit, the input of which is connected to the input of the power supply polarity indicator and serves to connect an alternating voltage source, the output of the power supply polarity indicator is connected to the first input of the frequency control unit, the outputs of three blocks comparisons are connected to the first three inputs of the operating mode switching unit, the inputs of the input signal comparator and the voltage-frequency converter are combined and connected to the output of the absolute shaping unit values of the input signal, the output of the input signal comparator is connected to the fourth input of the operating mode switching unit, the output of the voltage-frequency converter is connected to the input of the second phase shift unit, three outputs of which are connected to the second, third and fourth inputs of the frequency control unit, the fifth and the sixth inputs of this block are connected respectively to the outputs of the first and third comparison blocks, three outputs of the frequency control block are connected to the fifth, sixth and seventh inputs of the switching unit press clamps, the first output of which is connected to the third input of the control and protection unit, the second and third outputs of the operation mode switching unit are connected to the third and second inputs of the control pulse distribution unit, the outputs of which are connected to the first and second inputs of the control and protection unit, outputs galvanic isolation and amplification of control pulses are connected to the control inputs of the respective four power transistor switches of the semiconductor switch, characterized in that, in order to increase the braking efficiency, a rotor rotation sensor is inserted in it, an input signal indicator and a braking control unit with seven inputs are inserted into the control system and four outputs connected to the corresponding inputs of the galvanic isolation and amplification of control pulses, the four first inputs of the braking control unit are connected to the corresponding outputs of the control and protection unit, the fifth and sixth inputs of the braking control unit are connected respectively to the outputs of the power supply polarity indicator and an indicator of the input signal, the input of which is connected to the output of the block Formation of the absolute value of the input signal, the seventh input of the control unit for braking expands the input of the control system; the entrances of the turn sensor are connected respectively to the second output of the third stator winding of the electric motor and the first output of the first stator winding of the electric motor; the output of the rotor rotation sensor is connected to the control system input; the braking control unit is made on four two-input OR elements, four two-input elec- And, one two-input element AND-NOT and one inverter, the first inputs of the three elements OR and the first element And form the first four inputs of the braking control unit, the first input of the fourth element OR forms the fifth input of the braking control unit, and two inputs of the second element AND form the sixth and seventh inputs of the specified braking control unit, the output of the second element AND is connected to the combined second inputs of the first three OR elements and the AND-NOT element directly and via an inverter to the combined second the inputs of the fourth OR element and the first AND element, the outputs of the first OR element and the NAND element are connected to the inputs of the third AND element, whose output is the first output of the braking control unit, the outputs of the third and fourth OR elements are connected to the inputs of the fourth AND element, the output of which the third output of the braking control unit, the outputs of the second OR element and the first element And form the second and fourth outputs of the braking control unit, respectively. 3 % l, i Un 13 18 nineteen 15 22 B 25 26 37 + + f J2 R 2b fff / br and and Hi and KC and Jhnnnnn fej at ut 0t iot