A rotor is a body with a mass. So, to lift that
mass against gravity and to keep it in
motion, one needs to apply a force. If it is
linear movement, it is called force and in the
case of angular movement, as in the case of
a motor, it is called Torque. As the starting torque is proportional to the square
of the applied voltage, the more voltage that is
applied to the motor, the better will be the starting
torque. It is for this reason that rated voltage is
applied to the motor.
Now, we know that for a motor to start, a certain
voltage and a certain frequency have to be applied
to the motor. Apply full rated voltage at rated frequency, at the
time of starting itself. Isn’t it?
This method is called “Full Voltage Starting” or
“Across the Line Starting” or “Direct‐on‐Line or
D.O.L. Starting”.
We will see the schematics of this starter now.