SU1573522A1 - Multimotor ac electric drive - Google Patents

Abstract

The invention relates to electrical engineering and can be used in a multi-motor asynchronous electric drive of a hand-held portable tool used in construction, agriculture and other fields. The aim of the invention is to increase reliability. The multi-motor electric drive contains NM-phase electric motors 1.1, ..., 1.M, a semi-controlled rectifier 2, an inverter 9 made up of M inverter cells 10.1, ..., 10.M, M capacitors 11.1, ... 11. M, inverter control unit 12, source 13 of the inverter control unit, thyristor 14, control relay with winding 15 and closing contact 16. By introducing into the electric drive M single-phase rectifying bridges 18.1, ..., 18.M, current transformer 19 , the circuit 20 of the delay and the formation of the control pulse and the execution of the output transformers 10.1, ..., 10.M with additional windings prevents emergencies in inverter cells 10.1, ..., 10.M and a three-phase bridge rectifier 2 when the load phase is broken, normal start of electric motors 1.1, ..., is ensured 1.N and protection of electric motors against operation with the absence of a phase of supply voltage. 1 il.

Description

The invention relates to electrical engineering and can be used in a multi-motor asynchronous electric drive of a hand-held portable tool used in construction, agriculture and other industries.

The aim of the invention is to increase reliability.

The drawing shows a structural diagram of a multi-motor drive.

The AC multi-motor electric drive contains N t-phase asynchronous electric motors 1.1 ... .1 .N, a three-phase bridge semi-controlled rectifier 2 with 3 ... 5 thyristors in the anode group and with 6 ... 8 control circuits, an inverter 9 composed of m inverter cells 10.1 ... 0.t with transformer output each connected in series and according to, m capacitors 11.1 ... ... I.t., inverter control unit 12, control unit power supply 13, thyristor 14, control relay with winding 15 and closing contact 16, resistor 17, m single-phase rectifier bridge bridges 18.1 ... 18, t, a current transformer 19 with m primary and one secondary windings, a delay circuit 20 and the formation of a thyristor control pulse 14, and the output transformers 21.1, .. 21.t all inverter cells are made with the main and auxiliary secondary windings. The input terminals of the semi-controlled rectifier 2 are designed to be connected to the power supply terminals, and the control electrodes of the thyristors 3 ... 5 through control circuits 6 ... 8 are combined into a common point. The input terminals of the inverter 9 are connected to you

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to the current terminals of the semi-controlled rectifier 2. The output terminals of the main secondary windings of transformers 21.1 .., 21.t of the inverter cells are connected to the corresponding phases of the relay windings of electric motors 1.1 ... 1.N through switches 22.1 ... ... 21. N, extension cables 23.1 ... ... 23.N and plug connectors 24.1 ... 24.N, each of capacitors 11.1 ... 11.t is connected parallel to the input terminals of the corresponding inverter cells 10.1 ... 10. t, the control inputs of which are connected to the outputs of the inverter control unit 12. One terminal of the control relay coil 15 is connected to the anode of the thyristor 14 and a positive terminal of the power supply 13, the negative terminal of which is connected via a resistor 17 to the cathode of the thyristor 14 and the other terminal of the control relay coil 15, the closing contact of which is connected between the anode terminal and the common connection point of circuits 6 ... 8 control thyristors of a semi-controlled rectifier 2. The DC outputs of the single-phase rectifying bridges 18.1 ... 18.t are connected to the DC terminals of the same polarity of the corresponding inverter bridges. cells 10.1 ... 10.t. One output of the additional winding of the output transformer 21.1 of the i-th inverter cell 10.i is directly, and the other output through (iH) -io, respectively, the secondary winding of the current transformer 19 is connected respectively to the first and second AC outputs of the corresponding (i + l) - ro single-phase rectifying bridge 18.1, where 1 1,2,. ,,,. One output additional winding output tansformator

21.m of the mth inverter cell 10.m directly, and the other output through the primary secondary winding of the current transformer 19 are connected respectively to the first and second AC terminals of the first single-phase rectifying bridge 18.1. The secondary terminals of the current transformer 19 are connected to the inputs of the delay 20 circuit and the formation of the thyristor control pulse, the outputs of which are connected to the control circuits of the thyristor 14.

The drive works as follows.

After turning on the mains voltage, the inverter control unit 12 starts operating and control signals are supplied to the control inputs of the inverter cells 10.1 .., 10. t. A current flows through the winding of the control relay 15, its contact 16 is closed, including a three-phase bridge rectifier 2 using thyristors 3 ... 5. A voltage appears in its output buses, the 10.1 ... 10.t. inverter cells start to work, converting a constant voltage into a variable of a given frequency at the output of transformers 2 1.1, .. 21.t. This alternating voltage is through connectors 24.1 ... 24.N extension cables 23.1 ... 23.N and switches 22.1 ... 22.N supplied to the electric motor 1.1 ... 1.N, which actuates the actuators.

The load on each cell is the same and the voltage at the output terminals of the inverter cells 10.1 ... 10.t and the capacitors 11.1 ... 11.t is evenly distributed .. On the additional windings of each output transformer 21.1 ... 21.t the same voltage is established with the amplitude of the magnitude of the lower voltage on each capacitor 11.1 ... 11.t. Rectification bridges 18.1 ... 18.t are closed by higher voltage of capacitors 11. one. . . 11, tp and no current flows through the primary windings of the transformer 19, the protection does not work, the thyristor 14 is closed,

If the supply wire of one of the phases is broken in the extension cable, for example, cable 23.1, the load on the inverter cell 10.1 decreases, and on the inverter cells 10.2 ... 10t, the load will increase, so

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as through the remaining phases of the electric motor 1.1, the current increases and the electric motor heats up. Since the load on the inverter cells has changed, and on the cell 10.1 it became less, on the cell 10.1 ... 10.t more, then the voltage on them and the capacitors 11.1 ... 11.t connected in parallel is redistributed. On capacitor 11.1 and cell 10.1 voltage

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increases, and on capacitors 1.2 ... 11.t and cells 10.2 ... 10.t decreases. On the additional winding of the transformer 21.1, cells 10.1, accordingly, the voltage also increases. When the voltage on the code of the additional winding of the transformer 21.1 becomes greater than the voltage on the capacitor 11.1, the rectifying bridge 18.2 will open and the circuit from the additional winding of the transformer 21.1 will flow through the primary winding of the current transformer 19 and the rectifier bridge 18.2 charging capacitor 11.2. The load on the cell 10.1 increases, the voltage on the cells 10.1 ... 10.m and the capacitors I 1. one . , ... ll.m is leveled. At the output winding of the transformer 19, a voltage is applied to the thyristor control electrode 14, with a small delay determined by the delay and delay circuit 20 of the triggering pulse, applied to the control electrode of the thyristor 14. Contact 16 of the relay is opened, Thyristors 6 ... 8 after a half-period of the supply voltage is turned off, the voltage is removed from its output busbars, the converter is turned off. Electric motors 1. one . . . 1, H is de-energized and stopped. Thus, they are protected from overheating and failure.

Due to the equalizing effect of the current from the additional winding of the transformer 21.1, a significant change in the voltage on the inverter cells 10.1 ... 10.t is prevented during the operation of the protection, which prevents the occurrence of overvoltages on the circuit elements and their failure, eliminates the failure switching invertor cells.

When any electric motor 1.1 ... 1, N is turned on by the switch 22.1 ...

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. ..22.N, the breaker contacts may close non-simultaneously, which at the time of connection will cause sudden load changes in the phases of connecting cables and inverter cells 10.1 ... 10.t, causing redistribution of the voltage on them. However, the leveling effect of additional windings of transformers 21 |. 1 ... 21.SH will prevent the occurrence of a significant bias | and overvoltages on the elements of the skhm |, and the effect of protection at the time of launch

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blocked by the action of delay circuit 20.

Thus, the occurrence of emergency situations in Inverter cells and a three-phase bridge rectifier is prevented when the load phase is broken, normal electric motor start-up and motor protection are prevented from working with the absence of the supply voltage phase and the reliability of the multi-motor electric drive is improved.

Claims (1)

Invention Formula An AC multi-motor electric drive containing N t-phase asynchronous electric motors, a three-phase bridged semi-controlled rectifier with thyristors in the anode group, the input terminals of which are assigned to be connected to the terminals of the reading network, and the control electrodes of the thyristors are connected to a common point through control circuits an inverter composed of a hectare of inverter cells with a transformer output each connected in series and according to each other, and connected to the output terminal of a three-phase semi-controlled bridge bridge A relay, the output terminals of the transformer of the inverter cells are connected to the corresponding phases of the stator windings of the capacitor electric motors u, each of which is connected parallel to the input terminals of the corresponding inverter cells, an inverter control unit whose outputs are connected to the control eight inputs of inverter cells, power supply to the inverter control unit, thyristor, control relay with winding and closing contact, one winding terminal of the control relay is connected to the thyristor anode and positive power supply terminal of the inverter control unit, the negative terminal of which is connected through a resistor to another winding control terminal and with the thyristor cathode, the closing relay of the control relay is connected between the anode output and the common connection point of the thyristors of the three-phase bridge control circuit is rectified l, so reliability, the difference is that, in order to increase m single-phase five Q five 0 five 0 rectifying bridges, a current transformer with m primary and one secondary windings, a delay circuit and a thyristor control pulse generation, and the output transformer of each inverter cell is provided with an additional winding, the DC outputs of single-phase rectifying bridges are connected to the DC terminals of the same polarity corresponding inverter cells, one output of the additional winding of the output transformer of the i-th inverter cell directly, and the other output through (1 + 1) -th second respectively The current winding of the current transformer is connected respectively to the first and second AC terminals of the corresponding (i + l) single-phase rectifying bridge, one output of the auxiliary winding of the output transformer and the inverter cell directly, and the other output through the first secondary winding of the current transformer respectively, with the first and second AC terminals of the first single-phase rectifying bridge, the secondary leads of the current transformer are connected to the inputs of the delay circuit and neither the thyristor control pulse, whose outputs are connected to the thyristor control circuits, where, 2, .., t-1,