AC Induction Motors
- These are generally used for constant speed applications where a fixed frequency power source such as 60 Hz or 400 Hz is available. Typical applications are fans and pumps. Motor construction consists of windings on the stationary part of the motor and copper shorting bars on the iron laminations of the armature. The AC voltage applied to the windings induces a current in the armature of the rotor, creating a magnetic field. This field reacts with the field in the stationary part of the motor to create torque.
- High torque and high rpm applications
- Motor lasts as long as the bearings hold up as there are no brushes to wear out.
- Induction motor noise has tonal components at the rotation speed due to imbalance. The electromagnetic excitation is also strong at a frequency that is the product of the number of rotor conducting bars and the "slip frequency". The slip frequency is the difference between the rate of rotation of the stator′s magnetic field and of the rotor.
Subjects: Electrical Engineering