3 replies to this topic

[FbJavier]

hello everybody!
id pre-commisioned (instrumentation test) a brand new wound- rotor induction motor having a capacity of 3000KW. Ive seen its liquid starter cubicle, the question: Is this liquid starter, is put on the primary or in the secondary starting (id suspected on the secondary); please let me know? how the liquid starter alter its resistance? does it most likely the same principle of BRINE TANK TESTER for load testing of Electric generators?

[marke]

With a wound rotor motor, I would be very surprised if the resistor was connected in the primary circuit. Connecting the resistor in the secondary circuit will improve the start torque and reduce the start current, whereas connection of the resistor in the primary circuit wil reduce the start current and reduce the start torque by the current reduction squared.

Liquid resistance starters come in a number of different forms. Some have adjustable probes or adjustable fluid levels to vary the effective value of the resistance. If the electrolite is saline solution (brine) then the resistance will also reduce with temperature. Is ther is significant power dissipated in the resistors during start, the resistance will reduce during start.

[simon turfrey]

liquid starter is coupled to the rotor of an ac slip ring motor.
the resistance is altered by weakening and strengthening of the electrolyte. see our website @ www.oipengineering.co.uk, i can fax you details of how to alter resistance if you give me your fax no.

[GGOSS]

High all,

Larger liquid resistance starters as per those described here are often refered to a moving electrode starters.

One of the added advantages of these over conventional fixed electrode liquid resistance starters is that a level of speed control can also be achieved.

Where speed control is required, a heat exchanger is added to the basic moving electrode starter. The saline solution is pumped through heat exchanger to ensure it remains at constant temperature and therefore a constant resistance.

The motor speed which is influenced by the resistance is then controlled by moving the electrodes either further apart or closer together.

Although many people regard these types of starters as being 'old technology' they work extremely well and are easilly serviced by general electrical personel.

Regards,
GGOSS