Exam Question

### Part A: Star/Delta Starter
#### 1. Principle of Operation
A Star/Delta (or Wye-Delta) starter is a reduced voltage starting method used for three-phase induction motors. The primary purpose is to reduce the large starting current, which can be 5 to 8 times the full load current. This reduction minimizes voltage dips on the supply line and reduces mechanical stress on the motor and its driven load during startup.
The method involves starting the motor with its stator windings connected in a **Star (Y)** configuration. In this configuration, the voltage across each winding is reduced to $$ \frac{1}{\sqrt{3}} $$ (approximately 57.7%) of the line voltage. After the motor accelerates to a certain speed (typically 75-80% of rated speed), a timer switches the winding connections to a **Delta (Δ)** configuration, applying the full line voltage for normal running.