Question

what is differance by ac generator and dc generator?

Answer 1

The constructional differences pertaining to AC or DC current types would mostly involve commutation mechanism. In DC motors we obtain rotating magnetic field by either building commutation mechanism inside machine or by using an external electronic commutation circuit (DC brushless motors). Likewise for DC generators, the rectification is either done with commutation mechanism, or by using diode rectifiers outside the machine.
An AC construction would strictly require laminations (to reduce circulating current known as Eddy current) in the core of field winding as well. A DC machine could benefit from laminated core for field winding if the armature reaction is significant but it would be less common for smaller machines.Polyphase AC supplies would affect the winding configurations in generators. In motors that work on 1 or 2 phase AC, the starting torque requires additional features such as shaded pole. These are not needed in 3 phase motors.
So's it's mostly commutator design, lamination for field winding core, starting torque mechanisms and winding configurations that vary with 

Answer 2

Differences between AC and DC generators -



1. In an AC, or alternating current, Generator, the electrical current periodically reverses its direction. With a DC, or direct current,Generator, the current flows only in one direction.

2. D.C wound field motors are constructed with brushes and a commutator, which add to the maintenance, limit the speed and usually reduce the life expectancy of brushed D.C. motors. A.C. induction motors do not use brushes; they are very rugged and have long life expectancies. The final basic difference is speed control.

3. The AC generator generates an output voltage which alters in amplitude as well as time whereas the DC generator generates a constant output voltage which does not change in amplitude as well as time.


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