Device for dynamic braking of a capacitor motor. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Electric motors

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The article describes a simple device for dynamic braking of an asynchronous capacitor motor with a low power squirrel-cage rotor (micromachines), which provides automatic braking when disconnected from the network by short-term flow of pulsating current through its windings.

Devices [1, 2] for dynamic braking of a capacitor motor (CE) are known, containing the main and auxiliary windings connected in parallel, a phase-shifting capacitor connected in series with the auxiliary winding, a switching unit and a diode.

The disadvantage of these devices is the low reliability due to the wear of the switching equipment due to arcing on the switch contacts when the motor is turned off.

Below is a description of a more reliable device, free from this drawback (see figure). The proposed technical solution is protected by copyright [3].

The device contains a switch SA1, with which the main winding "G" of the electric motor and the auxiliary winding "B" are connected to the power supply terminals through the phase-shifting element C1. Contacts 1-5 of the switch SA1 in the circuit of the main winding of the CE are shunted by a series circuit of the diode VD1 and the electrolytic capacitor C2. The capacitor is shunted by resistor R through contacts 3-4 of switch SA1, which are connected in series with resistor R. The connection point of phase-shifting element C1 and auxiliary winding "B" is connected to terminal 2 of switch SA1.

In the initial (pre-start) position, the phase-shifting element C1 is shunted by the contacts 1-2 of the SA1 switch, and its contacts 3-4 in the resistor R circuit are open.

The device works as follows. When the CE is turned on with the help of contacts 1-5 of the SA1 switch, the main winding "G" and the auxiliary winding "B" are flowed through the phase-shifting element C1. In this case, the contacts 3-4 of the SA1 switch shunt the capacitor C2 with a resistor R.

The electric motor starts. A series circuit of the diode VD1 and the capacitor C2 shunted by the resistor R shunts the closed contacts 1-5 of the SA1 switch and does not affect the operation of the CE.

When the CE is disconnected from the network by contacts 1-5 of the SA1 switch, its contacts 3-4 open in the resistor R circuit, contacts 1-2 shunt the phase-shifting element C1 and the windings "G" and "B" connected in parallel are flowed by the rectified current of the network through the elements VD1 and C2, as a result of which the CE is intensively inhibited. At the end of the charge of the capacitor C2, the diode VD1 is blocked by it, as a result, the flow of current through the windings "G" and "B" of the electric motor stops. Restarting the CE causes the discharge of the capacitor C2 to the resistor R through the closed contacts 3-4 of the SA1 switch, and the circuit is ready for a new braking cycle.

Thus, the device provides dynamic braking of the electric motor, its automatic shutdown at the end of the braking process, as well as a reduction in the sparking of the switch contacts by at least half due to the shunting action of the diode-capacitor chain, which increases the reliability of the device.

Details. As a switch SA1, any one suitable for current and voltage is used. The type of diode VD1 and the capacitance of capacitor C2 are determined by the power of the electric motor used. So, for a CE with a power of up to 0,6 kW, as a diode VD1, you can use a diode of the KD227Zh type for a current of 5 A and a voltage of 800 V or 2D203G, D for 10 A, 700 V, as well as V1010 - V10-14 for a current of 10 A and voltage from 700 V and above. Any others for the specified current and voltage will do. It is possible to use diodes of the old series for a current of at least 5 A, turning them on two in series, for example, D232 - D234 or D246 - D248 with any letter index.

In this case, the diodes must be shunted with resistors of the MLT-1 type with a resistance of 150 ... 200 kOhm. Capacitor C2 - electrolytic type KE-2 or EM for a voltage of at least 400 V. Its capacity is determined experimentally until the required braking time of the electric motor is obtained. Discharge resistor type MLT2 with a resistance of 150 ... 200 kOhm.

References:

1. Author's certificate of the USSR No. 306790, KL. NO2r 3/22, 1978.
2. Japan Patent cl. 55C221 54-13565 publ. 31.05.79/XNUMX/XNUMX.
3. Author's certificate of the USSR No. 1023598, KL. NO2r 3/24, 15.06.83/XNUMX/XNUMX

Author: K.V. Kolomoitsev

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