Slip Ring Induction Motors and Salt Water

Do a search on "liquid resistance wound rotor motor control"

Slip ring Induction Motor: The Rotor is Wound and has the ends of the windings coming to the slip rings (3 phase Start).

When Starting this type of motor, the starting torque is increased if the rotor windings resistance is increased: The winding remains the same but you add a resistance in series with each branch of the windings. To achieve this, you can just get a suitably sized resistance ( the resistance does not need to be more than few Ohms per phase of the rotor, but the watts dissipated are high, depending on the size of the motor).

On the other hand, a water + Salt mixture put in a container where you dip three electrodes, each wired to the one of the slip rings output. For sure, using Plastic container is safer, will do a replacement for the resistances: Salty water is conductive and the resistance of the water is DIMINISHED if you INCREASE the salt content !! therefore, you have to go easy with the salt until you achieve the required starting torque!!

After starting, and when the speed of the motor is high enough, you short circuit the outputs from the slip-ring so that you reduce the ouside added resistance: There is no need for them after achieving the starting (~ 5, 10 or max 15 seconds depending on the Inertia of the driven apparatus). The Shorting is normally achieved using a suitable contactor.

I hope that this is what you were loking for.