RU2140127C1 - Induction motor braking device - Google Patents

Abstract

FIELD: electrical and radio engineering. SUBSTANCE: device has running and braking contactors, capacitors connected to motor winding, DC power supply incorporating two transformers with series- connected primary, secondary, and auxiliary windings; output of rectifier bridge using center-tap circuit arrangement is connected to two phases of stator winding through braking contactor contacts and third phase of stator winding is connected to center tap of rectifier. Novelty in device is introduction of three additional resistors, four diodes, and three auxiliary capacitors; center tap of rectifier bridge is connected through auxiliary transformer windings, resistor, and diodes connected is parallel opposition to first phase of stator winding; minus and plus terminals of bridge are respectively connected through series-connected resistors, diodes, and closing contacts of braking contacts to remaining phases of stator winding. Auxiliary capacitors are connected to respective output leads of diodes. EFFECT: improved braking reliability and efficiency. 1 dwg

Description

 The invention relates to electrical engineering and can be used to brake asynchronous squirrel-cage motors.

 A device is known for braking an asynchronous electric motor, comprising capacitors connected to the stator winding, a working and brake contactors, a direct current source consisting of two transformers, the primary windings of which are connected in series and connected to the network through the make contact of the brake contactor, the secondary windings are connected to each other in series , additional windings are connected to each other in series, and one of them is connected to one phase of the stator winding, and the other is connected to the last point of the rectifier, consisting of diodes connected according to the bridge circuit, the input of the bridge is connected to the free terminals of the secondary windings of the transformers, and the output is connected to the other two phases of the stator winding through the contacts of the contactor [1].

 The disadvantages of this device are low braking reliability and a relatively small decrease in rotor speed and low braking efficiency.

 The purpose of the invention is to increase the reliability and efficiency of braking and increase the intensity of braking.

 This goal is achieved by the fact that in the device for braking an asynchronous motor containing a stator winding of the electric motor connected through the make contacts of the working contactor to the electric network, and through the opening contacts of the working contactor to the stator winding are connected by a triangle capacitors, a brake contactor with make contacts, a constant source current, consisting of two transformers, the primary windings of which are connected in series and connected to the network through the brake contact ontactor, secondary windings are connected to each other in series, additional windings are connected to each other in series, one of which is connected to one phase of the stator winding, and the other is connected to the midpoint of the rectifier, consisting of diodes connected via a bridge circuit, the bridge input is connected to free the conclusions of the secondary windings of the transformers, and the output is connected to the remaining two phases of the stator winding through the closing contacts of the brake contactor, an additional three resistors, four diodes and three auxiliary capacitor, the midpoint of the rectifier through a series-connected additional windings of the transformers is connected to the first output of the first resistor, the second output of which through opposite-parallel connected first and second diodes is connected to the "minus" plate of the first auxiliary capacitor and the "plus" plate of the second auxiliary capacitor and to the first phase of the stator winding, the negative output of the rectifier is connected to the first terminal of the second resistor, the second terminal of this resistor is connected to the cathode of the third diode, the anode of which is connected to the “negative” plates of the second and third auxiliary capacitors, the common point of this connection is connected to the third phase of the stator winding through the make contact of the brake contactor.

 The drawing shows a diagram of a device.

 A device for braking an asynchronous electric motor contains a stator winding (1) of an electric motor connected through the make contacts (2) of the working contactor to the electric network, capacitors (4) are connected to the stator winding (1) through the break contacts (3), and the brake contactor with make contacts (5,6,7), a direct current source consisting of transformers (8,9), primary windings (10 and 11) are connected in series and connected to the network through contact (5) of the brake contactor, secondary windings (12) and ( 13) are connected in series, complementary the windings (14) and (15) are connected in series, the winding (14) is connected to the midpoint of the rectifier, consisting of diodes (16,17,18,19), connected by a bridge circuit, an additional three resistors (20,21,22) , four diodes (23,24,25,26) and three auxiliary capacitors (27,28,29), the midpoint (12,13) of the rectifier is connected to the first through series-connected additional windings (14 15) of the transformers (8.9) a resistor (20), the second output of which is connected in parallel to the first (23) and second (24) diodes connected to the plates of the first (27) and second ( 28) auxiliary capacitors to the first phase of the stator winding (1), the negative output (16.17) of the rectifier (16,17,18,19) is connected to the second (21) resistor, the second output of which is connected to the plates through the third (25) diode of the second (28) and third (29) auxiliary capacitors, and through the contact (6) to the second phase of the stator winding (1), the positive output (18.19) of the rectifier (16.17, 18.19) is connected to the third (22) a resistor, the second output of which through the fourth diode (26) is connected to the plates of the first (27) and third (29) auxiliary capacitors and through the make contact (7) to the third phase of the stator winding (1).

 The device operates as follows. When the working contactor is turned on, its contacts (2) connect the motor (1) to the network, contacts (3) open. When the working contactor is reflected, its contacts (2) open, and the contacts (3) close. The engine is disconnected from the network. The process of its capacitor braking with the help of capacitors (4) begins. Then the brake contactor is turned on and the contacts are closed (5,6,7). The direct current source is connected to the electrical network and the supply of direct current to the stator winding begins. The process of dynamic braking of the electric motor begins. Simultaneously with the supply of direct current through resistors (20,21,22) and diodes (23,24,25,26), the auxiliary capacitors charge (27,28,29). Capacitors (27.28) are alternately charged in one half-cycle, and discharged to the stator winding in another half-period. As a result, the braking current passes through the stator windings in two half-cycles and the mode of symmetric dynamic braking occurs.

 After the engine stops, the brake contactor is switched off.

 Thanks to the introduction of additional elements into the circuit, intensive and effective braking is ensured. The braking current is distributed evenly over all 3 phases of the stator winding and has the same value. Reduces engine heat, which increases reliability.

Claims (1)

 A device for braking an asynchronous electric motor, the asynchronous electric motor of which is electrically connected to the working contactor, contains a stator winding connected through the make contacts of the working contactor to the network, and capacitors and disconnect contacts of the working contactor, a brake contactor with make contacts, a DC contact are connected to the stator winding with two transformers, the primary windings of which are connected in series and connected to the network through a make contact the brain contactor, the secondary windings are connected in series, the additional windings are connected together in series, one of which is connected to the midpoint of the rectifier, consisting of diodes connected in a bridge circuit, the bridge input is connected to the free terminals of the transformer secondary windings, and the output is connected respectively to two phases of the stator winding through the contacts of the brake contactor, characterized in that the capacitors are connected through the opening contacts of the working contactor to the stator winding, three additional resistors, four diodes and three auxiliary capacitors are introduced, the midpoint of the rectifier is connected through the additional transformer windings connected in series to the first output of the first resistor, the second output of which is connected through the first and second diodes in parallel to the "minus" plate of the first auxiliary capacitor and the "positive" lining of the second capacitor and to the first phase of the stator winding, the negative output of the rectifier is connected to the first output of the second resistor, the second terminal of which is connected to the cathode of the third diode, the anode of which is connected to the “negative” plates of the second and third auxiliary capacitors, the common point of this connection is connected to the second phase of the stator winding through the make contact of the brake contactor, the “positive” output of the rectifier is connected to the first output of the third resistor , the second terminal of this resistor is connected to the anode of the fourth diode, the cathode of which is connected to the "plus" plates of the first and third auxiliary capacitors, a common point of this connection Ia via a make contact connected to the brake contactor third phase stator winding.