To connect a 380 V three-phase motor to a 220 V single-phase network, you must perform a calculation capacitor for an electric motor 380 by 220 volts, to be more precise, a pair of capacitors - working and launcher. An asynchronous electric motor is connected in two ways: according to the "delta" and "star" circuits.
Content
- Electricity storage electronic component
- Establishing winding leads
- Ways to connect electric motors
Electricity storage electronic component
A capacitor is an electronic element that is designed to store electricity. The nature of the work does not provide for the active actions of the component. Taking into account the operating mode, capacitors of variable and constant capacitance are distinguished.
Depending on the type of voltage, a distinction is made between polar, where a certain polarity should be strictly adhered to, and non-polar (used in AC and DC circuits). When choosing the required capacitance, it should be remembered that in a circuit with a parallel connection, the total capacitance is added.
In order for the electric motor to start and continue to work, starting (Cn) and working (Cp) capacitors are used. The purpose of the starting capacitor is to start the electric motor.
When the motor reaches operating frequency and power, the starting capacitor is turned off. The main function of a working capacitor is to create a sufficient shift in the electromagnetic field.
Capacity of the working capacitor for connecting the electric motor according to the "star" winding connection diagram calculated by the formula:
C p = 2800 * I n / U s (microfarad), where:
- I n - rated current of the electric motor, measured in Amperes (corresponds to the passport data of the electric motor);
- U s - mains voltage. The unit of measurement is Volt.
The starting capacitor is connected in parallel with the operating one and turns on only at the stage of starting the electric motor. At the moment of speeding up the engine, you need to turn off the starting capacitor.
The capacity of the starting capacitor must exceed the capacity of the working capacitor by 2.5-3 times. Calculated by the formula: C p = (2.5... 3) * C p; (microfarad).
Establishing winding leads
The first step is to separate the winding leads in pairs. Each pair should have ends that match the winding. This will require a tester or voltage indicator. When using the tester, set the switch to measure resistance (denoted by the Greek letter Ω "omega"). If a voltage indicator is used, before starting work, you need to touch the live parts for a few seconds to charge and test the device.
After that, one of the winding leads is taken, which will be conditionally adopted by the beginning of the first winding, and marked "U1". Next, you need to touch one of the measuring rod of the tester or voltage meter to the “U1” terminal, and the other to any of the remaining terminals.
If after this the values of the tester or indicator remain unchanged, this end is left, and the second measuring rod touch the other terminal of the remaining four wires, fingering until the indicators of the measuring instruments will change. Having found the second winding lead in this way, it is taken for the end of the first winding and marked "U2". Do the same with the other four wires..
Ways to connect electric motors
In everyday life, it is often necessary to connect an electric motor 380 for 220 volts. Despite the fact that the efficiency is significantly reduced (more than 50%), such a conversion can be justified. In fact, after the modernization, the motor begins to perform two-phase work.
Domestic manufacturers of electric motors often assemble the "star" circuit by default, while the "triangle" will still need to be completed by connecting three phases and collecting a star. The strong point of the connection diagram of the 380 by 220 volt "triangle" motor of the three-phase electrical circuit is the maximum power generated by the motor.
For connecting motor windings "Triangle" you need:
- connect the beginning of the second winding with the end of the first;
- the beginning of the third winding with the end of the second;
- the beginning of the first winding with the end of the third winding.
If the motor is connected according to the "delta" scheme, then it is capable of issuing one hundred percent of the passport power, but during start-up, the current is so high that there is a risk of insulation failure wires. For this reason, in powerful electric motors use a mixed star-delta connection. The motor starts at low starting currents, and when it enters the operating mode, it switches to the "delta" circuit.
Starting according to the connection diagram of a three-phase electric motor for 220 "star" is carried out smoothly due to the impossibility of achieving the maximum possible performance of the electric motor.
The "triangle" scheme is suitable for electric motors with a rotational speed of no more than 1.5 thousand rpm. rpm. This type of connection uses capacitors. The meaning of connecting email. motor 380 by 220 through a working capacitor - this is the appearance of the third phase.
