Exam Question
If the motor terminal markings are unknown how would you identify the start, run and common terminal connections. (16)
Class 4 (4th Engineer)
MET
📅 Jul 2024
Reference Answer
### 1. Fundamental Principle (4 Marks)
The identification of unknown terminals on a single-phase induction motor is based on measuring the electrical resistance of its internal windings. A typical capacitor-start or split-phase motor has two primary windings:
* **Main Winding (Run Winding):** Designed for continuous operation after the motor reaches its running speed. It is constructed with thicker gauge wire and has fewer turns, resulting in a **lower electrical resistance**.
* **Auxiliary Winding (Start Winding):** Used primarily to create a phase shift and starting torque. It is made of finer gauge wire with more turns, leading to a **higher electrical resistance** compared to the main winding.
The identification of unknown terminals on a single-phase induction motor is based on measuring the electrical resistance of its internal windings. A typical capacitor-start or split-phase motor has two primary windings:
* **Main Winding (Run Winding):** Designed for continuous operation after the motor reaches its running speed. It is constructed with thicker gauge wire and has fewer turns, resulting in a **lower electrical resistance**.
* **Auxiliary Winding (Start Winding):** Used primarily to create a phase shift and starting torque. It is made of finer gauge wire with more turns, leading to a **higher electrical resistance** compared to the main winding.
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