What is the difference between a dc motor and permanent magnet dc motor?

A true DC machine needs a constant magnetic flux that flows through the rotor. This flux can be provided by either permanent magnets or electromagnets. You don't have to use a PM machine for a windmill, but if you don't you need a power source to excite the electromagnets.

A stepper motor strikes in steps if we are speakme in regards to the identical thing. A step motor stops without a continuing rotation when the vigour is cut by way of using a swap. A DC motor is a direct current motor means that it runs off a battery or saved energy alternatively of a revolving present akin to AC. A step motor is a difference of transmission not current feed.

Permanent Magnet Motor is a self excited Motor, Field is permanent Magnet only . If it is used in Wind Mill Generator no external power required for field excitation.

DC Motor Got Armature &separate field winding excitation can be controlled,In fixed speed As a Generator out put can be varied with varying field excitation.,where as PM Generator In fixed speed out put can't be varied.I have given few examples only.

If you use permanent magnets, you wouldn't have to deal with windings, their welding, protection, etc. Extra mechanism and exrra money spent if you use field coils.

Permanent magnets are easier to use. But they cannot stand higher magnetic field so they only have limited application where you aren't dealing with large powers, say in KiloWatts or MW. Plus, if you use permanent magnets, there will be no copper losses, as opposed to when you use coils.