Polyphase AC motors are primarily three-phase and are by far the largest electric prime moverin all of industry. They are offered in ranges from 5 up to 50000 hp and account for a largepercentage of the total motor industry in the world. In number of units, the three-phase squirrelcage induction motor is the most common. It is commercially available from 1 hp up to severalthousand horsepower and can be used on conventional AC power or in conjunction with adjustablespeed AC drives. Fans, pumps , and material handling are the most common applications.