Impact of rotor bar bridges in torque development in integral horsepower machines in PWM inverter environments

The impact of rotor bar bridges in closed-slot induction motor rotors has been simulated using Finite Element Analysis (FEA) and single phase equivalent circuit methods in 60 Hz sinusoidal environments. In this paper we will discuss a study on a 455HP, 90Hz, 380 Vac machine utilizing a rotor with a deep bridge, then the impact on output torque once the diameter of the rotor was turned down, reducing the bridge depth. The research performed allowed for optimizing optimal bridge depth and air gap sizing based upon machine design for peak torque development.