A permanent magnet AC (PMAC) motor is a synchronous motor, meaning that its rotor spins at the same speed as the motor's internal rotating magnetic field. Other AC synchronous technologies include hysteresis motors, larger DC-excited motors, and common reluctance motors. (c) beta.machinedesign.com

1. PERMANENT MAGNET
MOTORS
Special Types of Motors

2. INTRODUCTION
A special type of motor
A permanent magnet AC (PMAC) motor is a synchronous motor, meaning
that its rotor spins at the same speed as the motor's internal rotating
magnetic field.
 PMAC, PM synchronous, and brushless ac are synonymous terms.

3. CHARACTERISTICS
In a PM motor the poles are made of permanent magnets

4. CHARACTERISTICS
Permanent magnets

5. CHARACTERISTICS
In a conventional dc motor with a wound-field circuit, flux per pole depends on the
current through the field winding and can be controlled.
However, flux in a PM motor is essentially constant and depends on the point of
operation.

6. CHARACTERICTICS
For the same power output, a PM motor has higher efficiency and requires less
material than a wound dc motor of the same ratings.

7. Since the flux in a PM motor is fixed, the speed- and current-torque characteristics are
basically straight lines as shown in Fig. 12.2 in the next slide.

8. ADVANTAGE
3 times higher torque to weight ratio than compared to induction motor

9. ADVANTAGES
PM motors are compact, efficient and do not require cooling fan
Used in higher-end applications requiring precisely metered torque,
speed, or positioning
Permanent-magnet fields are, by definition, constant and not
subject to failure, except in extreme cases of magnet abuse and
demagnetization by overheating.
Produces less noise

10. DISADVANTAGE
3 times as expensive as induction motors
May be subject to demagnetization under service condition
Lifetime of a asynchronous motor is much higher than PM motors
PM motors can not be used at high temperatures
Asynchronous is easier to repair than of the PM motors in a short
circuit failure

11. APPLICATION
PM motors are used within traction and for hybrid cars and for
electrical machines

12. APPLICATION
Food processing industry

13. APPLICATION
Motor range of PM motors
 Hybrid cars up to 15kW
 Larger SUV up to 150 kW
 Traction up to 1000 kW
 Wind turbines up to 500 kW probably 1000kW
 Small motors in heat pumps
 Servo motor up to 12kW