An inrush current is produced when an electric load is turned on. Induction Motor draws a high starting current during starting period which effects on electromagnetic torque, speed and current. Many methods can be used to start AC induction motors. Choices such as full voltage, reduced voltage either by autotransformer or star - Delta, a soft starter, or usage of an adjustable speed drive can all have potential advantages and tradeoffs. Reduced voltage starting can lower the starting torque and help prevent damage to the load. Choosing the proper starting method for a motor will include 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.
In this project an educational starting board of three phase squirrel cage induction motor for electrical machine lab in Palestine Technical University (Kadoorie) will be designed which will allow students to learn several general methods of starting three phase squirrel cage induction motors: full voltage (DOL), reduced voltage (Y-Δ, Autotransformer and Soft Starter) and variable frequency drives (VFD).
The direct conduction current was the highest starting current and the rest of the methods solved this problem as this project will show.