Induction motor starting methods and issues

Many methods can be used to start large AC induction motors. Choices such as full voltage, reduced voltage either by autotransformer or wye-delta, a soft starter, or usage of an adjustable speed drive can all have potential advantages and trade offs. Reduced voltage starting can lower the starting torque and help prevent damage to the load. Additionally, power factor correction capacitors can be used to reduce the current, but care must be taken to size them property. Usage of the wrong capacitors can lead to significant damage. Choosing the proper starting method for a motor includes an analysis of the power system as well as the starting load to ensure that the motor is designed to deliver the needed performance while minimizing its cost. This paper examines the most common starting methods and their recommended applications.