Liquid resitance starter (LRS) ,IN which external
resistance is liquied media which is use for the starting
method of slip ring motor.
for starting of slip ring motor external resistance are
required so that we use liquid (addition of some caustic
soda)as resistance so that it is called as LRS.
Combination of water and castic soda for improving the
resistance in starter, i.e. called Liquid Resistance
If any slip ring Induction motor, at the time of starting
given the external resistance required to rotor side, why
because starting current and startying torque is very high.
So we are using resitance starter.Depend on motor
capacity , at that place using Liquid resistance starter.
Since in a Slip Ring Induction Motor, the Rotor resistance is low, this can cause very high current and low starting torque.SO by externally adding resistance , we increase the rotor resistance and thus decrease the starting current and increase the starting torque. ie Pull out torque can be achieved at very low RPM.
An LRSS is nothing but a solution of Caustic Soda. which is connected in series with rotor.
On starting, the LRSS resistance is added to rotor resistance ( LRSS In condition)
...as slowly motor starts to gain speed ..the LRSS contacts move, there by reducing the resistance between its contacts and thus the effective resistances decreases.
When the motor has gained full speed, LRSS is cut out by usually using a shorting contactor.
thus a slip ring induction motor runs a cage motor at full speed.