A star delta starter

A star-delta starter 

A star-delta starter, also known as a wye-delta starter, is an electrical motor starting method used to reduce the starting current of an induction motor. It is commonly employed for motors that drive high inertia loads or in situations where the starting current needs to be limited to prevent damage to the motor or other connected equipment.

The star-delta starter uses a combination of two different motor connections during the starting process:

1. Star Connection (Y-connection): During the starting phase, the motor windings are connected in a star configuration, also known as a Y-connection. In this arrangement, each motor phase is connected to the corresponding end of three windings. The other ends of the windings are connected together at a common point, forming the star point.

2. Delta Connection (Δ-connection): After a predetermined time (typically a few seconds), the motor windings are switched to a delta configuration, also known as a Δ-connection. In this configuration, each motor phase is connected to the start of another winding, forming a closed loop or delta shape.

The switching between the star and delta connections is usually accomplished using a motor starter or a specialized star-delta starter panel. Here's how the starting process works:

1. Starting in Star Mode: When the motor is started, it is initially connected in a star configuration. This reduces the voltage across each winding, leading to a reduction in the starting current (compared to direct-on-line starting).

2. Transition to Delta Mode: After a preset time, the motor starter switches the connections to the delta configuration. This causes the voltage across each winding to increase to the full supply voltage.

The star-delta starter does not provide full starting torque during the star connection mode, but it helps reduce the current drawn from the power supply, which is beneficial in cases where there are limitations on the maximum starting current. Once the motor is up to speed and reaches its operating conditions, the star-delta starter is bypassed, and the motor runs in the standard delta configuration to provide full torque.

It's important to note that the star-delta starter is suitable for applications where the load can tolerate a reduced starting torque during the initial period of motor startup.

Keep in mind that there may be slight variations in the implementation and control of star-delta starters based on the specific application and motor requirements.