Auto Transformer By Elmo Instruments Industries

It means to vary the transformation ratio in very small steps but without breaking the load circuit. Its specification is like:-

Input :- 240 Volts 50 Hz A.C

Output:- 0 to 270 Volts.

Being a true transformer, the maximum voltage available is made about 12% higher than the input voltage.

An auto transformer for 3 phase supply

They are made by connecting three single phase together. The brush arms are moved by a common shaft. The three winding are connected in a star and the star points connected to the neutral wire system. Thus, a 3 phase voltage variable from 0 to 440 volts is obtained.

There are available with motor-drive. The type of motor used for driving is specially made for this application . It is 240 volts ac motor operating, with speed of 60 RPM synchronous at 50 Hz. It is instantly reversible and stopped without over-run. Gears between motor and auto transformer shaft are used to get lower speed. The time taken for the full sweep is the specification used. That is the time taken for the brush to move from zero voltage position to the maximum voltage position.