Variac is the generic name given to the variable autotransformer consisting of only one coil which is shared by both the primary and secondary sides of the circuit. It provides a simple method of controlling voltage. Concerning the utility line voltage, it continuously provided the adjustable output voltage. It has the advantage of producing the various levels of output voltage with a single input voltage. It is cost-effective and portable than the regular AC supplies which makes them the best choice for short-term projects. It can regulate the servo motor and control the temperatures of heaters. It could provide more uniform heating when used with the thermostatic control system. It is the best choice for the one who is looking the saving energy. The secondary winding in variac could be adjusted as long as the carbon brush is in contact with the primary windings.
Variac is used in the following fields:
1. Testing of the electronics devices With the completion of the repairing of the electronics devices, the best option is to slowly power the device for avoiding the burning or damage of the replaced parts. Thus the use of variac could slow down the power of the repaired units preventing the damaging of the replaced parts.
2. Temperature adjustment in resistance type heater The variable AC power could be applied for adjusting the resistance type of the heating element.
3. Power to the amplifier or old radio While powering the old radio or the amplifier not using for an extended period, the reduced voltage power could be applied to the unit in stage for re-conditioning the electrolytic capacitor.
4. Adjusting the speed of the fan in a narrow range With the change in the applied AC voltage, the speed of small AC motors could be changed over a narrow range. With this application, the problem is with the motor torque that reduces and resulted in the stalling of the fan and motor.
5. Compensation of the line voltage drop There is a higher voltage drop in long power lines thus the variac is used for compensating this loss of voltage over the lines.