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..
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