How to choose a capacitor for a washing machine motor?

It's great when you can connect the motor to the right type of voltage. But sometimes a situation arises where a three-phase motor has to be "powered" from a single-phase network. For example, if craftsmen take a washing machine motor and create a lathe or other "homemade" thing on its basis. In such cases, you will have to use a capacitor for the washing machine motor. But there are a lot of them, so it would be useful to figure out how to choose the right device.

If you need to start a three-phase motor

It is not easy to select a capacitor for a washing machine motor. The most important thing is to correctly determine the capacity of the device. But how to calculate it? A complex formula is used for a more accurate calculation of the indicator, but you can also use a simpler version.

How to quickly estimate which device will suit your case? To calculate the capacitor capacity using a simplified method, you need to know the engine power and "add" about 7-8 μF for every 100 watts. However, it is important not to forget to take into account the voltage indicator affecting the stator winding during calculations. This value should not exceed the nominal level.

When the electric motor can only be started on the basis of maximum load, a starting capacitor must be included in the circuit. This device is characterized by a short period of operation - it functions for about 3 seconds, until the rotor speed reaches its peak.

When selecting a starting capacitor, it is necessary to take into account that:

• In terms of capacity, it should be 2-3 times higher than the working capacitor,
• Its nominal voltage must exceed the network minimum by 1.5 times.

Having understood the nuances, you can select both a network and a starting capacitor for a three-phase electric motor. In order not to make a mistake, it is important to follow all the recommendations.

Selecting a capacitor for a single-phase motor

In the vast majority of cases, capacitors for asynchronous motors are used to connect to a "standard" voltage (220 V), taking into account the inclusion of the device in a single-phase network. However, the process of their use is much more complicated. Let's figure out why.

Three-phase motors operate on the basis of a constructive connection, while for single-phase motors it is necessary to achieve a shifted torque. This is provided by an additional layer of rotor winding for starting. The phase is shifted by a capacitor.

Why is it difficult to select a capacitor?

Although there are no significant differences, different capacitors for asynchronous motors require different methods of calculating the permissible voltage indicator. Usually, about 100 watts per 1 μF of device capacity are required. Such motors have several possible operating modes:

• A starting capacitor is installed, an auxiliary winding layer is organized (specifically for the starting stage). In this situation, the calculation of the device capacity will be as follows - 70 μf per kilowatt of electric motor power,
• A working device is installed, the capacitor capacity of which is within 25-35 μf. In this case, an additional winding and constant connection of the capacitor will be required throughout the entire service life of the motor,
• A network capacitor is used when the starting device is connected at the same time.

In any case, it is important to monitor the heating level of the electric motor during its operation. If you notice overheating of the engine elements, you should take urgent measures. If there is a working capacitor, you will need to reduce its capacity. Experts recommend using devices that operate on the basis of a power of 450 watts or more, as they are considered universal.

A starting capacitor is a small element of an electric circuit, necessary for the engine to "gain" the required speed as quickly as possible. The working device serves to maintain an optimal load on the motor.

You can design a fully functional circuit yourself. Between the electric motor and the PNVS button, you need to install a working and, if necessary, a starting capacitor. Usually, the winding terminals are located in the terminal part of the engine, so the connection can be upgraded in any way.

It should be remembered that the operating voltage of the starting capacitor should be 330-400 volts. This is due to the "surge" of power when starting or stopping the motor.

So what is the difference between a single-phase asynchronous motor? This type of motor is more common in household appliances, and requires an auxiliary starting winding and a phase shift capacitor to activate it. It can be connected using a variety of available circuits. There are three types of capacitors available for sale:

• Polar,
• Non-polar,
• Electrolytic.

Polar ones are prohibited for connecting electric motors to an AC network. The dielectric inside the device will quickly break down and a short circuit will occur. Therefore, in this case, it is necessary to use non-polar capacitors. Their plates will interact equally with both the current source and the dielectric.