The starting torque of an induction motor is maximum when rotor resistance per phase is ______ rotor reactance/phase.

Question

RRB Paper · Accepted Answer

The starting torque of an induction motor is maximum when rotor resistance per phase is Equal to rotor reactance/phase.

Let's examine the starting torque equation again:

Ts = (K * E₂² * R₂) / (R₂² + X₂²)

where

R2 is the rotor resistance per phase
X2 is the rotor reactance per phase.

Taking the derivative of this equation with respect to R2 and setting it equal to zero, we get:

d(Ts)/d(R2) = (K * E₂² * X₂ * (R₂² - X₂²)) / (R₂² + X₂²)² = 0

Simplifying this expression, we get:

R₂² = X₂²

Therefore, the starting torque is maximized when R2 = X2, or when the rotor resistance per phase is equal to the rotor reactance per phase.

Equal to