What is Star connection - Delta connection for ac motors?

A star (or wye) connection is a method of connecting three-phase electric motors, where the individual windings are connected in series and form a star-like shape. In a star connection, one end of each winding is joined at a common point called the neutral point, and the other ends are connected to the power supply.

In a star configuration, the line voltage (voltage between any two phases) is higher than the phase voltage (voltage across a single winding). The line current is equal to the phase current. This connection type results in a lower starting current and torque, making it suitable for applications where a smooth and gentle startup is desired.

Star connections are commonly used for three-phase electric motors, especially during the starting phase in a star-delta starting configuration. After the motor reaches a certain speed, the connection is switched to a delta configuration for normal operation, allowing the motor to deliver its full power and torque.

A delta (or triangle) connection is a method of connecting three-phase electric motors, in which the individual windings are connected end-to-end, forming a closed-loop or triangle shape. In a delta configuration, there is no common neutral point, and each winding is connected directly to the power supply.

In a delta connection, the line voltage (voltage between any two phases) is equal to the phase voltage (voltage across a single winding). The line current is greater than the phase current by a factor of the square root of 3. This connection type results in higher starting current and torque, making it suitable for applications requiring high power and torque during normal operation.

Delta connections are commonly used for three-phase electric motors in normal operating conditions, especially after the starting phase in a star-delta starting configuration. When the motor reaches a certain speed, the connection is switched from a star to a delta configuration, allowing the motor to deliver its full power and torque for efficient operation.

Should the speed control device be connected in star or delta configuration?

Dear colleague, if you do not know how to connect the motor that will work with the driver, please calmly review the items below.

1- If the speed control device has a single-phase (220V) input;

Check the motor label. If it says 220v delta, 380v star, please connect it in delta.

2- If the speed control device has a three-phase, i.e. 380V input;

Check the motor label. Please connect it as indicated on the label for 380V.

An example motor label and star-delta connection diagram are given at the top of the page.

Example; If we need to examine the motor with the label given above;

a: If you have a 220 volt input driver, you should connect in delta.

b: If your driver has a 380v input, you should connect in star. It is clearly seen on the label.

+ So, what happens if I connect a motor that should be connected in delta, in star?

- What happens if I connect a motor that should be connected in star, in delta?

+ Your driver will either go into protection mode, or your motor will burn out!!

++ We strive to provide answers to your problems on our website whenever we can. If you have any inquiries regarding speed control devices, you can review our previous answers to questions asked here or if you have questions about AC motors, you can check here.