RU1815783C - A c electric motor drive - Google Patents

Abstract

Usage: the invention relates to electrical engineering and can be used to control three-phase asynchronous electric motors when feeding them from a single-phase network. SUMMARY OF THE INVENTION: When the Start button is pressed, the make contacts 9 are closed. An alternating voltage is applied to the starter coil 4. The starter closes the first, second and third contacts 5,6,7, supplying the mains voltage to the electric motor. During start-up, inrush current in stator windings of an age

Description

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it is melting. In coil 10 of the overcurrent relay, an inrush current flows, causing it to trip. The relay is set to trip current. When the overcurrent relay is activated, contacts 11 are closed, which connect the starting capacitor to the network. The electric motor starts. After the motor accelerates to the rated speed, the inrush current drops to the rated current. In this case, the starting capacitor is disconnected from the network. The electric motor works with a connected working capacitor. The on state of the starter is achieved by the self-holding of the starter coil 4 by the first contact. AT

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 purpose of the invention is to increase reliability ..

The drawing shows a schematic diagram of an AC electric drive.

The AC electric drive contains a single-phase electric motor 1 with starting 2 and working 3 capacitors, some of which are combined and connected to the first phase of the stator winding, the other output of the working capacitor 3 is connected to the second phase of the stator winding, contactor 4 with a coil and three make contactors 5 6,7, one of the terminals of the first 7 and second 6 make contacts of the contactor is equipped with clamps for connecting to the phases of the network, the other output of the first make contact 7 of the contactor 4 is connected to the second phase of the stator winding and, the Stop button 8. one terminal of which is equipped with a clamp for connecting to one phase of the network, the other terminal of the Stop button is connected via a Start button 9, shunted by the third NO contact 5 of the contactor 4, to one terminal of the contactor coil, the other terminal of which is equipped with a terminal for connecting to another phase of the network, the overcurrent relay with a coil 10 and with a make contact 11, one output of which is connected to the other output of the starting capacitor 2. another output of the make contact of the overcurrent relay is connected to one output of the coil to ontactor 4, the other terminal of the second make contact of the contactor is connected to the single-process operation of the electric motor, for example, mounted on a sawmill, when processing wood, due to the heterogeneity of the material being processed, the depth of cutter cutting, etc. Peak loads occur, which lead to a decrease in the rotation frequency and sometimes to a stop of the electric motor, as a result of which the load current in the stator windings increases, which leads to the operation of the overcurrent relay, which closes the starting capacitor to the network. As a result of this, the torque on the shaft increases, thereby automatically eliminating the resulting peak load of the motor. 1 ill.

the output terminal of the coil of the overcurrent relay, the other terminal of which is connected to the third phase of the statoron winding.

Electric AC operates as follows. When the Start button is pressed, make contacts 9 close. An alternating voltage is applied to the coil of the contactor 4. The contactor closes the first 7, second 6 and third 5

contacts, supply voltage to the motor 1.

During start-up, the inrush current in the stator windings increases to 21n ... 51n (depending on the type of electric motor). Over the coil of the overcurrent relay 10, an inrush current flows. its operation. The relay is set to a trip current of 1.1 1N.

When the maximum relay

current contacts 11 are closed, which connect the starting capacitor to the network. The electric motor starts.

After accelerating the electric motor to the starting current, it drops to the nominal value. Overcurrent relay trips. In this case, the starting capacitor 2 is disconnected from the network. The electric motor 1 operates with the connected working capacitor 3. The on state of the contactor is achieved due to self-holding

contactor coils 4 by third contact 5.

In the process of operation of the electric motor

for example, mounted on a sawmill.

When processing wood, due to the heterogeneity of the material being processed, depth of penetration, etc. extreme loads occur, which lead to a decrease in the rotational speed, and sometimes to a stop of the electric motor. As a result, the load current in the stator windings increases.

which leads to the operation of the overcurrent relay, which closes the contacts 11 connects the starting capacitor 2 of the network. As a result, the torque on the shaft is increased, thereby eliminating the arising overload of the electric motor during its operation. But if for some reason the overload is not eliminated, then in order to avoid the output of the constructional windings, the electric motor is disconnected from the mains by a thermal relay, which is not shown in the diagram.

Claims (1)

SUMMARY OF THE INVENTION An AC drive containing a single-phase motor with starting and working capacitors, one terminal of which is combined and connected to the first phase of the stator winding, another terminal of the working capacitor is connected to the second phase of the stator winding, a contactor with a coil and three make contacts, one output the first and second make contacts of the contactor are provided with clamps for connection to the phases of the network, the other terminal of the first make contact of the contactor is connected to the second phase of the stator winding, the Stop button, one output of which is equipped with a clip for connecting to one phase of the network, the other output of the stop button is connected to one of the terminals of the Start button and the third make contact of the contactor, characterized in that, with In order to increase reliability, a maximum current relay with a coil and a closing contact is inserted into it, one terminal of which is connected to another terminal of the starting capacitor, the other terminal of the closing contact of the maximum relay the eye is connected to one output of the contactor coil, the other, the output of the second make contact of the contactor is connected to one output of the coil of the overcurrent relay, the other output of which is connected to the third phase of the stator winding, the other outputs of the Start button and the third make contact of the contactor are connected to one output of the contactor coil, the other end of which is provided with a clamp for connection to another phase of the network.