What are the advantages of Ac motors over dc motors?

Answer 1

Generally most A.C motors that most people see regularly have no commutator (though not all) ,so there is sometimes less mechanical frictional losses this can increase overall efficiency.

This usually means less parts to fail.

Some A.C motors require ¨start¨ and or ¨run¨ capacitors and may also require a start mechanism that will have frictional losses and add to the bits that could fail.

They also often have detrimental magnetic eddies which cause some losses, this is often due to economical stator or rotor construction.

A.C motors can have a very high power density as the magnetic flux is generated with an A.C current this can be higher than most conventional D.C. motors especially due to the high rate of change of current through the stator and rotor.

This is the very nature of the A.C current it is constantly changing.

D.C motors are often made using permanent magnets (again not always) so they can ¨get something for nothing¨ so to speak with an existing magnetic field. Energy does not have to be wasted to create one of the required magnetic fields to make the motor rotate.

D.C. motors can be made without permanent magnets too. Some of these motors can also have very high energy densities as the current can be made to change very rapidly either with the commutator or with special drivers.

There are very few hard and fast rules about A.C versus D.C in motors as both types have been extensively developed over many years.

The decision to use an AC or D.C motor usually come down to what is available to drive the motor in question.

Cars use D.C. as they have a D.C battery.

Washing machines and fridges use A.C as it is generally more efficient to send A.C over long distances to your home.

It is also currently far easier to convert A.C up and down through Transformers etc, The transmission and distribution of D.C is far less efficient and more complex so this often dictates our choice rather than the motor type.

Answer 2

You use DC motors instead of AC motors in electric bikes because you don't have the ability to connect the bike to a source of AC. (Unless you want to put up with a very long extension cord.)You could convert DC (battery) power to AC, but this is going to add cost and weight, and lower efficiency.

Answer 3

Very often we use ac motors as well. dc motors are simpler if you have a dc supply to run them off.