compare the efficiency of a DC motor against an AC motor.?
There are many different types of AC and DC motors and a wide range of power ratings. In addition, some types of motors are used only with electronic speed controllers or have electronic components built in. Some types of motors are suitable for using either AC or DC. They are series-connected, commutator-type DC or universal motors and permanent-magnet, brushless-type DC motors without a built-in electronic commutator. For very small motors, those producing less than 100 watts or 1/8 horsepower of mechanical power, all types of DC motors are probably more efficient than all types of AC motors. For small motors producing more than 100 watts up to about 10000 watts or 15 horsepower, the efficiency advantage shifts to AC motors somewhere in that range depending on the specific motor configuration. Single phase AC motors are less efficient than 3-phase motors. Among single-phase motors, shaded pole motors are less efficient than capacitor motors. Permanent-magnet DC motors with simple electronic commutators probably have the efficiency advantage compared 3-phase induction motors up to a higher power level than any any other comparison of DC vs AC types. If variable speed is a requirement, permanent-magnet motors probably have the advantage over 3-phase induction motors in all power ratings for which permanent-magnet motors are available. That may extend somewhat above 10000 watts. The speed control unit may be essentially the same for either type of motor and the permanent-magnet motor essentially operates on AC.
What AC motor and what DC motor?
