The Differences Between Pm Machine And Conventional Ac Machines
In this part, a survey of existing work and literature relating to the project is covered. The differences between PM machine and conventional AC machines
Induction machine is also called “asynchronies machine”. The rotor is placed in a rotating magnetic field and thus a rotating force can be attained.
The rotor is a rotating conductor and is mainly produced in cage shape. The stator generates the rotating magnetic field. The rotating of the magnetic field is not achieved by mechanical principle rather by applying AC current to the stator. The AC current applied to the electro-magnetic results in the rapid changing of the polarity of the magnetic field and make it equal to a rotating magnetic field. Brush conmmutator is not applied in induction machine.
The main difference from the structure is the PM machine use a piece of permanent magnet to generate magnetic field. For brushed PM machines the magnet is placed in the stator and for BLDC pm motors the magnets are placed on the rotor. Since the field is generated by the permanent magnet, the field is fixed and cannot be adjusted to control the speed or the torque. However, with replacing the field generating coil, the loss is reduced in PM motors.
For the fact that a permanent magnet can produce a much higher field than the electro-excited cage structure in same size, the PM machine has higher power density than similar size induction machine. The effect of back emf (slow down speed and reduce…