220/380V motor wiring method

1. First understand the two wiring methods of the motor

Schematic diagram of two wiring methods in the motor junction box

The first is the star (Y) connection method, as shown in the figure, the Z, X, and Y ends of the three-phase stator winding inside the motor are connected together to form a common point O, and then three end wires are drawn from the starting ends A, B, and C. In the junction box, UVW three-phase alternating current (380V) is respectively introduced to provide motor running power, which is suitable for three-phase asynchronous induction motors of 3KW and below. The actual picture is as follows:

The second is the triangle (△) connection method, that is, the three-phase stator windings are connected to each other at the beginning and end. As shown in the figure, the A end of the first phase winding is connected to the Z end of the third phase winding, which can be regarded as the U phase, the B end of the second winding is connected to the X end of the first winding, which can be the V phase, and the C end of the third winding is connected to the Y end of the second winding, which can be the W phase. Then, three wires are connected to the junction box, and the UVW three-phase AC power supply (380V) is respectively connected to provide the motor with running power. It is suitable for three-phase asynchronous induction motors of 4kw and above. However, the wiring method of the motor should be based on the actual nameplate wiring.

Motor actual triangle connection

Why is W2 below in the simple schematic diagram of motor wiring?

Motor junction box wiring diagram

It can be seen that when connecting the triangle, the upper wires cross, which is very difficult and unsafe in actual operation and can easily cause phase-to-phase short circuit.

Schematic diagram of the relationship between the six terminal blocks in the junction box

As we can see in the above physical picture, there are two rows of terminals in the junction box of the three-phase motor. We use the above "connector relationship diagram" to further explain their relationship. For the time being, the six terminals of the three-phase winding are marked as D1, D2, D3, D4, D5, and D6, among which D1 and D4, D2 and D5, D3 and D6 are each one phase, which is actually the two ends of the same wire. Each wire is called a phase winding, and the three wires are called A, B, and C three-phase windings. The reason for reiterating this point is that many people are easily confused here.

2. How to connect 220/380V motor

380V is the voltage for industrial use, and 220V is the voltage for household use. If the nameplate says 220/380V, and the connection is △/Y, it means that the motor can be connected in a delta connection under the condition of a three-phase 220V power supply, and in a star connection under the condition of a three-phase 380V power supply, to adapt to two different voltages.

If the power supply voltage is 220V, it should be connected in a triangle. If it is connected in a star shape by mistake, the voltage connected to each phase winding will drop from 220V to 220/√3=127V, and the motor will not start due to too low voltage. If it still bears the rated load, it will easily cause overload and burn.

If the power supply voltage is 380V, it should be connected in star shape. If it is connected in triangle shape by mistake, each phase winding will bear 380V voltage, which will increase the stator current and burn the winding. Therefore, the correct wiring method should ensure that the power supply voltage of the motor must be equal to or close to the rated voltage of the motor when it is working normally.

The wiring method of 380V has three phase wires, no neutral wire, and all live wires. We have explained its wiring method above. The household 220V has two wires, one live wire and one neutral wire. How to connect it to the three terminals in the junction box? Or how to make the motor move? I will share two methods with you.

The first method: using a single-phase inverter

The inverter control motor is very convenient to use and can be set very intelligently. There are many inverters on the market that can convert single-phase input into three-phase output. The following are only two reference pictures, and everyone will understand at a glance.

220V input to 380V output inverter

Another single-phase inverter physical wiring diagram

The second method: adding capacitance to change the wiring method

The motor's three-phase power supply is changed to a two-phase power supply

The working principle of a single-phase motor: Two windings that are 90 degrees apart in electrical angle in space produce magnetic flux axes that are also 90 degrees apart in electrical angle in space. When currents of different phases are passed through them, a two-phase rotating magnetic field can be generated, thereby generating a starting torque to start the motor.

Wiring method for converting three-phase motor to single-phase input

1. The connection method of the three-phase winding remains unchanged during the modification, that is, the original star connection remains star connection, and the original delta connection remains delta connection. Any two of the three output terminals originally connected to the three-phase motor are connected to the two ends of the power supply (L-live wire, N-neutral wire), and the remaining one is connected to the capacitor first.

2. The other end of the capacitor is connected to one end of the power supply. Whether it is connected to the live wire or the neutral wire depends on the required direction. Different connection methods have different directions. The above figure also shows different connection methods to achieve the forward and reverse connection of the motor.

Single-phase input to achieve motor forward and reverse connection

Therefore, as shown in the figure, we connect any two-phase windings in series in the three-phase motor as the main winding, and connect the other phase winding in series with an appropriate capacitor as the secondary winding. If we connect them to the same single-phase power supply, it will generate a two-phase rotating magnetic field and starting torque just like a single-phase motor.

Three-phase motor Y to single-phase △ actual wiring diagram

1. Calculation method of capacitance

The calculation formula of starting capacitor and running capacitor, the formula of running capacitor: C=1950I/Ucosφ, C is the running capacitor capacity (uf-microfarad) I is the rated current value of the motor (A) U is the rated voltage, since we are changing to single-phase operation here, the rated voltage is 220 volts. cosφ is the power factor, which is marked on many motors. The starting capacitor is generally 1-4 times the running capacitor.

2. Empirical formula for capacitance

100W power corresponds to 7 microfarads of capacitance, that is, a 1KW motor can use a capacitor of about 70 microfarads. This value is only an approximate number and can be adjusted according to your load conditions.

It is only recommended to modify motors below 1.5KW. The power will be attenuated after the modification and cannot carry heavy loads. If the power is slightly greater than 1.5KW, a starting capacitor needs to be added.

If you really don't know how to calculate the capacitance, you can show the motor nameplate to the merchant when purchasing the capacitor. Generally, the merchant has a calculation formula that can easily calculate the capacity of the capacitor you are using.

Note: In the motors with 220/380 logo, 220V also refers to three-phase input, but the voltage is 220V. This can also be achieved in household electricity through some methods (such as adding wiring terminals), that is, throwing out three wires with a voltage of 220V. One of the key points introduced in this article is how to change the three-phase input of the motor to single-phase input, that is, how to make the motor run through the live wire and neutral wire at home.

Of course, many household motors now have the circuits in the junction box directly connected, leaving two wires, one zero and one live, for backup. If you need a motor at home, you can directly purchase such a motor.