Electric machines are are energy conversion devices that convert electrical energy to mechanical energy and vice versa through the medium of magnetic field.
- An electric machine operates as a generator when it is used to convert mechanical energy to electrical energy.
- When an electric machine is used to convert electrical energy to mechanical energy, it operates as a motor.
Transformers are stationary electrical energy transfer devices that are very closely related to electric machines in that they use the same medium, i.e., magnetic field, for the transfer of energy from one side to the other side. Transformers do not change the type of energy; instead, they change the levels of voltage and current, while providing isolation.