How is the speed of an AC motor varied? How is the speed of a DC motor varied?

Answer:

The most effective way to vary the speed of an AC motor is to change the frequency using a variable frequency drive (VFD). Speed is proportional to frequency. If the frequency is reduced below the normal frequency, the voltage must be reduced proportionally. If the optimum voltage is maintained as frequency is reduced, constant torque can be maintained to a very low speed. The frequency can be increased somewhat above the normal frequency at constant voltage with loss of torque to maintain constant power. The speed of a DC motor is varied by changing the armature voltage. Speed is proportional to armature voltage. If the field is maintained by a separate power supply or by using permanent magnets, constant torque can be maintained. Speed can also be controlled by changing the field current. Reducing the field increases the speed.

hi. AC automobiles are designed and equipped otherwise than DC automobiles. AC automobiles take great element with regard to the 60 hertz clock of a ability line (or 50Hz in different countries) - this suggests the flexibility line differences stages 60 circumstances a 2d - to rotate, on an identical time as DC automobiles are designed with the voltage point utilized. you could administration them the two, yet with diverse ability. the least complicated to regulate is the DC motor (replace the potential (the voltage) and it turns slower or quicker.