Exam Question

### (a) Effect of Running an Induction Motor on Reduced Voltage (6 Marks)
Running a three-phase squirrel cage induction motor on a voltage lower than its rated nameplate value has several detrimental effects on its performance and lifespan. The core principle governing these effects is the torque-voltage relationship.
1. **Torque Reduction**: The torque developed by an induction motor is directly proportional to the square of the applied voltage ($$ T \propto V^2 $$). This is the most critical effect.
* **Reduced Starting Torque**: If the voltage is reduced to 90% (0.9) of its rated value, the starting torque will be only $$ (0.9)^2 = 0.81 $$, or 81% of the rated starting torque. This may be insufficient to start a high-inertia load (e.g., a large pump or fan), causing the motor to stall at startup.