How to connect a 127 V motor to a 220 V network. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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How to connect a 127 V motor to a 220 V network. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Electric motors

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Many radio amateurs have asynchronous electric motors from morally and physically obsolete players, tape recorders, recorders, electric typewriters and other household and industrial appliances. They could be used in many homemade designs, if they were not designed to be powered by a voltage of 127 V, 50 Hz, which is rare today. Using the example of RD-09 and EDG-2 engines, which were widely used in the past, we will show how to connect them to a 220 V network without any additional elements.

Two-phase asynchronous gear motors RD-09 for 127 V were widely used in industrial self-recording measuring instruments both for moving the writing unit and for pulling the paper tape. They are designed for round-the-clock operation, they are reliable and unpretentious.

Numerous modifications of these engines are known, differing in the gear ratio of the built-in gearbox and the speed of the output shaft from several revolutions per second to 1 ... 2 per minute. The moment on the RD-09 shaft is quite sufficient, for example, for closing and opening curtains.

The motor has two windings, one of which is connected directly to the 127 V network, and the other through the phase-shifting capacitor C1 (Fig. 1). If necessary, use the switch SA1 to change the direction of rotation of the shaft.

How to connect a 127 V motor to a 220 V network

It is usually recommended to connect such an engine to a 220 V network according to the circuit shown in fig. 2. The capacity of the additional quenching capacitor C2 is chosen such that the voltage on the winding 3-4 of the motor M1 remains approximately equal to the nominal value (127 V).

How to connect a 127 V motor to a 220 V network

By slightly changing the original circuit and connecting the phase-shifting capacitor C1 not in series with the motor winding, but in parallel with it, as shown in Fig. 3, you can do without an additional capacitor. The selection criterion for capacitor C1 remains the same as C2 in the previous case.

How to connect a 127 V motor to a 220 V network

Another example is the EDG-2 engine, which was widely used in household sound-reproducing equipment at one time. Due to the low noise level at a fairly high rotor speed (about 3000 min "1), it is advisable to use it for the manufacture of fans and pumps of small capacity. Fig. 4 shows a diagram of connecting this motor to a 127 V network, and Fig. 5 - to a network 220 V.

(click to enlarge)

Its two windings are not identical, so the optimal capacitance of a phase-shifting capacitor depends on which of the windings it is connected to. For this reason, the EDG-2 engine is reversed not by switching the phase-shifting capacitor, but by swapping the leads of one of the windings.

In all considered circuits, capacitors specially designed for operation in AC circuits should be used, for example, MBGCH for a voltage of at least 250 V. Capacitors K73-17 or other general applications should be rated for a voltage of at least 400 V. It is unacceptable to use oxide or ceramic capacitors.

Similarly, other asynchronous motors designed for a voltage of 220 V are connected to the 127 V network. A phase-shifting or quenching capacitor should be selected with a working mechanical load on the motor shaft. In this case, it is necessary to make sure that the engine starts reliably and that its windings do not overheat.

Author: V.Burkov, Ivanovo

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