The Y and △ connection instructions on the motor nameplate are clear. Once you understand them, you will no longer burn the motor!

The motor is the most common electrical component in our industrial control. Many students are not sure about the wiring method of the motor. How to connect it, and they are still confused when searching online. Today we will explain the connection method of the nameplate on the motor.

Motor nameplate description

From the right part of the nameplate, we can see that there are two connection methods : △ type 220V and Y type 380V.

Many students must have doubts about this, because when I checked online, the Y-△ start is a step-down start, which is exactly the opposite of the Y380V to △220V boost marked on the motor. What's going on?

Let’s look at the VOLTS voltage level on the left, which is 380V/220V. This corresponds to the voltage level of the input power supply. For example, our industrial power supply is three-phase 380V. In foreign countries, there are also three-phase 110V, 220V, 440V, 660V and other voltages. Level, can the above motor be used if it is shipped abroad? We will analyze the relationship between the nameplate markings, connection method and voltage level of the motor in the picture above.

First, let’s take a look at the difference between Y-shaped connection and △ connection. Everyone has seen these two connection diagrams, whether on the motor or in various materials;

There are three groups of motor windings corresponding to three wires U, V, W and 6 wire ends, the head U1 and the tail U2, then U1U2 form a line, and sometimes the tail is represented by X, Y, Z.

The Y-shaped connection is to connect the tails of the three wires (U2, V2, W2) together to form a neutral point, which is similar to a transformer. The triangle connection is the tail of the first wire and the head of the second wire (U2 and V1, V2 and W1, W2 and U1), so that they are connected head to tail to form a triangle shape.

Different ways to connect the motor

If it is a three-phase power supply with a voltage of 380V, the corresponding phase voltage of each phase is 220V. Everyone should understand this. Then if the Y-shaped connection is followed, the phase voltage of each winding of the motor is equal to the power supply phase voltage of 220V. Because the tail of each winding is the neutral point 0V, which is equivalent to connecting a live wire and a neutral wire;

Looking at the △ connection method, the phase voltage of the motor winding is equal to the line voltage of the power supply, 380V. Because there is no neutral point, it means that each winding is connected to two live wires.

We do not consider power factor and efficiency, the rated power of the three-phase motor is equal to:

Relationship between power, voltage and current

Let's analyze the comparison of the winding current when the motor is working normally and when it has just started. The motor still has the parameters as shown above. Assume that the starting current is I△, then the Y-type starting current is 1/3 I△. When the speed increases, for the same power Winding current under P:

380V voltage:

For Y-type connection, three-phase 380V industrial power is used, the starting current is 1/3I△, and the normal current is equal to P/(3*220)

For the △ type connection, using three-phase 380V industrial power, the starting current I△, the normal current is equal to P/(3*380)

220V voltage:

Using Y-type connection method and three-phase 220V industrial power, the starting current is 1/(1.7*3) I△, and the normal current is equal to P/(3*129)

Using △ type connection, using three-phase 220V industrial power, the starting current is 1/(1.7) I△, and the normal current is equal to P/(3*220)

440V voltage:

Using Y-type connection, using three-phase 440V industrial power, the starting current is 1.17/3I△, and the normal current is equal to P/(3*258)

Using △ type connection, using three-phase 440V industrial power, the starting current is 1.17 I△, the normal current is equal to P/(3*440)

To sum up, for a motor, if the grid level is higher than the rated level of the motor, the △-shaped connection cannot be used because the starting current will be large; if the grid level is lower than the motor, the Y-shaped connection cannot be used because the current will be too large during normal operation. .

In addition, the understanding of △220V and Y380V on the motor nameplate is that if the three-phase industrial power is 380V, the small-power motor can use the Y-shaped connection method and the high-power motor can use the △-shaped connection method (using Y-△ to reduce the starting current) , if the three-phase industrial power is 220V, the △-type connection must be used, and the Y-type cannot be used. Note that the voltages marked on the motor are line voltages rather than phase voltages.