RU2396692C1 - Synchronous motor start-up device - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: synchronous motor start-up device in transformer-motor group includes synchronous electric motor with main (5) and additional (6) three-phase stator windings. The first outputs of winding (5) in operating position are connected through contacts (7) of commutator to outputs (4) of three-phase transformer (2) the primary winding of which is connected to electric power supply, and secondary winding has branches (3), (4) to connect main (5) and additional (6) stator windings. The second outputs of main (5) winding are connected to common point through contacts (15) of commutator. Alternating current outputs of uncontrolled rectifier (8) are connected to the second outputs of additional (6) three-phase stator winding, and direct current outputs - to outputs of excitation winding (10) of synchronous motor. Commutator of stator windings of motor provides their switching by means of contacts for the period of asynchronous start-up from operating position to connection circuit of the main winding with triangle and in-series connection of main (5) winding connected to additional (6) stator winding with triangle in order to decrease starting current ratio.

EFFECT: decreasing starting current.

1 dwg

Description

The invention relates to synchronous motors, and more particularly to control devices for synchronous motors and power units "transformer-motor", and is intended for use in the drive of turbomechanisms and other medium power machines that do not require speed control.

Synchronous electric motors are widely used for driving turbo-mechanisms and other machines. In the drive of pumps for agricultural reclamation, they are presented with the requirements of maximum simplicity of design and operation and a reduced inrush current.

The first requirement is a synchronous motor according to the patent of the Russian Federation 2028719 "Synchronous electric motor", Н02Р 1/50 // Н02К 19/12.

The motor contains the main and additional three-phase stator windings, the second terminals of the first of which are connected to a common point, a three-phase uncontrolled rectifier, the AC terminals of which are connected to the second terminals of the additional three-phase stator winding, and the DC terminals through the first key with the terminals of the excitation winding of the synchronous motor shunted by a circuit composed of a second key and a resistor connected in series, a three-phase three-winding transformer, the primary winding of which It is connected to an electric power source, and one of the stator windings of the electric motor is included in each of the secondary ones. The disadvantages of this motor include the use of direct start of the engine when using only part of the stator winding, as a result of which this part of the winding is subjected to intense heating.

To reduce the starting current of synchronous motors, different devices are used. Known autotransformer start when the engine is connected to the network through an autotransformer, which reduces the voltage on the motor for the period of asynchronous start [Slodarzh M.I. Modes of operation, relay protection and automation of synchronous motors. M., Energy, 1977]. The disadvantage of this method of starting a synchronous motor is the high cost of the starting autotransformer and control devices for starting.

The closest in design to the claimed is the device according to patent RU 2271600 C1 Synchronous motor (Н02Р 1/50, Н02К 17/26, Н02К 19/14. Published. 03/10/2006. Bull. No. 7), adopted as a prototype.

The device comprises a synchronous electric motor with a primary and secondary three-phase stator windings, the first leads of which in operational position are connected through switches to a three-phase transformer, the primary winding of which is connected to an electric power source, and the secondary winding has branches for connecting the primary and secondary stator windings, second conclusions of the main winding the stator are connected to a common point, a three-phase uncontrolled rectifier, the AC output of which is connected to the second additional water-phase stator winding, and the DC terminals with pin field winding synchronous motor.

The disadvantage of this device is the high inrush current, which can cause voltage fluctuations in the network.

The technical task is to reduce the starting current of the transformer-motor unit.

The solution to the problem is achieved by the fact that the synchronous motor starting device in the transformer-motor unit, containing a synchronous motor with a main and additional three-phase stator windings, the first conclusions of which in operational position are connected via switches to a three-phase transformer, the primary winding of which is connected to an electric power source, and the secondary winding has branches for connecting the main and additional stator windings, the second terminals of the main stator winding are connected in common point, a three-phase uncontrolled rectifier, the AC terminal of which is connected to the second terminals of the additional three-phase stator winding, and the DC terminals with the terminals of the excitation winding of the synchronous motor, contains a commutator of the stator windings of the motor, which ensures their switching through their contacts for the period of asynchronous starting from the operating position in the connection diagram of the main winding with a triangle and the series connection of a triangle connected winding with an additional stator winding.

According to the patent and scientific literature, the claimed combination of features has not been identified, which allows us to conclude that the proposed solution meets the criteria of "inventive step" and "novelty." The claimed solution can be implemented in an electric drive of turbomechanisms and other devices, which meets the criterion of "industrial applicability".

The drawing shows a schematic diagram of the connection of the starting device of a synchronous motor as part of the transformer-motor unit.

Through the switch 1, the transformer 2 is connected to a three-phase source of electricity. The secondary winding of the transformer has branch leads 3 and 4, to which the main stator winding 5 of the motor and the additional stator winding 6 of the motor are connected, and the main winding 5 is connected to the terminals 4 of transformer 2 through contacts 7 of the switch. The output ends of the winding 6 are connected to the input of a three-phase rectifier 8 of half-wave rectification (rectifier bridge), the output of which is connected in series to the contacts 9 of the switch and the field winding of the motor 10. Parallel to the winding 10, a circuit from the discharge resistor 11 and terminal 12 of the switch is connected. Between the beginning of the phases of the main winding 5 and the ends of the other phases of this winding, contacts 13 of the switch are included; between the beginnings of the main winding 5 and the ends of the same name of the additional winding 6 included contacts 14 of the switch; between the ends of the main winding 5 included contacts 15 of the switch.

The engine in synchronous mode operates as follows. Contacts 1, 7, 9 and 15 of the switch are closed, contacts 12, 13 and 14 are open. The transformer is connected to a power source and provides voltage on the windings 5 and 6 of the synchronous motor, and the voltage on the winding 5 is higher than on the winding 6 due to the connection of the secondary winding of the transformer 2 to different branches. Due to the different voltage at the terminals 3 and 4 of the transformer, at the input of the rectifier 8 there is a voltage providing a current in the field winding 10. In this case, the field current is the rectified current of the winding 6. The currents of the stator windings 5 and 6 create a rotating magnetic field in the motor, which th engages with the magnetic field of the excitation winding 10, providing rotation of the rotor with a synchronous speed.

Starting the engine as follows. In the initial stationary state of the engine, the contacts of the switch are brought into the following positions: contacts 7, 9 and 15 are open; 12, 13 and 14 are closed; switch 1 is off. There is no voltage on the transformer and motor windings. For asynchronous starting of the motor, switch 1 is turned on and voltage is applied to the transformer 2 and the motor windings 5 and 6 from the terminals 3. In this case, the winding 5 is connected by a triangle and is connected in series with the winding 6 as with a through winding. The field winding 10 is disconnected from the rectifier 8 and is turned on at the discharge resistance 11.

The motor starts asynchronously. The inclusion circuit of the stator windings provides a decrease in the starting current, since the voltage of the transformer is distributed between the two stator windings. With the same parameters of windings 5 and 6, the reduction in the inrush current ratio with respect to direct start is about 2.6 times; with different parameters of windings 5 and 6, the reduction in the inrush current ratio can be determined by calculation or experimentally.

When the motor reaches a sub-synchronous speed (slip of the order of 2-5%), the contacts 12, 13 and 14 are switched to the open state and the contacts 7, 9 and 15 are closed, as a result of which the excitation winding 10 flows around the current and the motor is drawn into synchronism. At this, the engine start is completed, and the engine goes into synchronous operation mode.

Claims (1)

A synchronous motor starter in a transformer-motor unit, comprising a synchronous motor with a primary and secondary three-phase stator windings, the first terminals of which in operational position are connected through the switch contacts to a three-phase transformer, the primary winding of which is connected to an electric power source, and the secondary winding has branches for connecting the main and additional stator windings, the second terminals of the main stator winding are connected to a common point, three-phase failure a removable rectifier, the AC terminals of which are connected to the second terminals of the additional three-phase stator winding, and the DC terminals are connected to the terminals of the excitation winding of the synchronous motor, characterized in that it contains a commutator of the stator windings of the motor, ensuring their switching through their contacts for the period of asynchronous start-up from the working provisions in the connection diagram of the main winding with a triangle and the series connection of a triangle connected winding with an additional stator otkoy.