The formula for calculating the power necessary to start a **synchronous motor** with full load running torque is as follows:

## Formula

Where

P - Power developed by the motor (in watts).

V - Line voltage (V)

E_{b} - Back EMF generated/phase (V)

- The load angle (in degrees) is the angle formed between the back EMF & the terminal voltage.

X_{s} - Synchronous reactance (in Ω).

## Important Points

**Starting Condition:** At starting, the load angle (δ) is normally minimal, but increases with motor acceleration.

**Full Load Torque:** The torque at full load influences the load angle and, consequently, the power calculation.

**Maximum Power:** Maximum Power is achieved when δ = 90_{∘} resulting in:

This formula estimates the electrical power input required to start a synchronous motor at full load conditions, taking into consideration its electrical characteristics & operational factors.