Electric Motor Liquid Starter

The shorting contactor simply bypasses the resistance of the liquid, leaving only the resistance of the motor windings. Less resistance = more current; i.e., full load current for delivering full power to the motor.

Ok, so if the dippers are out of the liquid, does it mean that we are addding the resistance of the liquid?

Of course not.

The control electrodes don't come out of the electrolyte. Even with the electrodes at the top position a base current passes through the rotor electrodes and the electrolyte partly shorting the rotor.

To completely open circuit the rotor is liable the result in slip-ring flashover due to excess voltage tracking through carbon dust build up.

The liquid electrolyte functions as a resistor.When cold, the resistance is high.As the motor starts,the temperature of the electrolyte rises,and as a result,the resistance of the electrolyte decreases.A timer actuates the shorting contacts at a pre-determined time,according to the requirements of the motor.

The electrolyte is potable water with a chemical additive to adjust the resistance of the liquid.There is usually an oil film on top to prevent evaporation and resultant concentration of the electrolyte.There are also on some systems, a level alarm and floats

for maintaining level.

Hope this helps.

Hi Brich;

The soda water starter is the one am talking about. The one I saw has got some dippers which are connected to a shaft which is moved bt another small motor. As the motor is started, those dippers will be dipped in water as the shaft will be moving. My question now is how is the resistance of the soda water together with dippers connected to the rotor. You can open the following link, it has the liquid starter which is exactly the same as the one am talking about. http://www.youtube.com/watch?v=1E6pWxgunAA

Hope you will help me

regards

The liquid resistor starter is introduced in high current starting motors to reduce the starting toque hence to avoid motor run away, when the rotor resistance is low or absoliutely closed at zero potential like in small induction motors the starting toque or starting speed is very high, when we first introduce a load by creating liquid resistance or buffer resistance to the rotor resistance, on charging the stator the rotor winding produce power thus it create aload to the stator and restrict the starting toque as the motor accelerates to its oparation speed and toque when we achive the speeds at stages of accelaration we reduce the rotor resistance by use of contactor swith gear to short resistance at stages untill the motor is left with only running rotor resistance.