What are the Advantages and disadvantages of permanent magnets?

Answer 1

permanent magnets and wound stators (temporary magnets) can be used inthe generators and motors.

in small size generators (eg: dynamo in cycle),permanent magnets are used because,

1 it does not require electricity to magnetise

2 does not require stator cooling

but in larger size generators and motors, temporary magnets are prefered because,

1 it is small in size of same power permanent magnets

2 we can control the stator magnetic field by adjusting the power

3 the magnetic flux density per square cm is more

etc..