Permanent magnet motors (PMAC) are synchronous motors characterized by fixed magnetic fields, leading to higher efficiency and a better torque-to-weight ratio compared to induction motors. They are compact and suitable for high-end applications requiring precise torque and speed but are more expensive and sensitive to demagnetization. PM motors are used in various industries, including automotive and food processing, with applications ranging from hybrid cars to wind turbines.

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