Liquid Starter and Two Motor

The only way I can think of is weaken the electrolyte.

The manufacturer of the starter should be able to help, but many companies that made liquid starters are no longer around.

Do you know what the SG of the starter is? Reduce it by around 10% and try it. You will soon know if you need to increase / decrease the strength by the start up current.

Sorry I can't be more help

If that's not practical, another option may just be to change the insertion rate / depth of the electrodes (probes). But it also may effect the temperature of the electrolyte.

I'm assuming the liquid starter isn't used for speed regulation during normal running.

On start up the initial rotor current should be about 85 / 90% of FLC rising to FLC as the electrodes move together. When the final contacts close to short the slip-rings the final load kick should be about 150% of FLC.

If on initial start the current is at or above FLC the electrolyte is still to strong.

If on the other hand if the initial start current is lower than 85% increase the electrolyte strength. Stop the motor before it reaches full speed in this case to prevent damage to the final contacts and brush gear.

The new liquid starter is designed for the 1810V, if we change the electrode depth for 1018V it means that electrodes should stop further. In which case it would cause more heat? near or further? I think this extra heat problem would be solved by circulating the electrolyte.

Hi, there should not be a problem from a size / heat capacity point of point since the the motor load is the same. Since the voltage is increased the rotor current will drop on the new motor which also should be OK. The main problem would be the possibility of flash over at the starter terminals or at the shorting gear(you don't say if this is on the motor or separate). Liquid starters are rated are normally rated on three things. Current rating (a function of electrode area) Voltage rating ( a function of safety / flash over distances). And thermal capacity ( generally the volume of electrolyte and / or electrolyte coolers).

If the starter is a conventional one with some kind of hand or motor drive to control the electrode position, then the best route would be ....first clean out the controller of all of the muck and old solution and check all of the insulators for cracks and fouling and clean/replace the electrodes . Then re-fill with water(de-ionized if possible). If the controller handbook has a specified additive for the starter use that, otherwise use sodium carbonate either anhydrous or crystaline (if you use the first you will need much less !) Do not use caustic soda !

Try closing the supply breaker on the motor with only clean water. This will tell you if you are going to have flash over problems. Then start adding additive (note never add direct to the starter ! always mix in a separate bucket or something before adding) until you have the correct starting current. Note the solution conductivity is strongly temperature dependant. The conductivity will almost double between cold and almost boiling !

Finally there are starters that do not use moving electrodes ....called Vapormatics or similar. These rely on the electrolyte actually boiling between the electrodes to control the starting current. For these you really need to refer to the vendors documentation before changing the solution.

Regards to all

This maybe a very dumb question (i am asking it for my own knowledge because I have never hearrd of it) but what is a liquid started?

Sorry for the dumb question.

Mike

As MKS site mentioned, and I quote:

liquid starters consist of a thick-walled steel
tank containing the electrolyte and the electrode
system. The tank inside is sandblasted and
provided with a triple coat of epoxy resin varnish of
approx. 0.2 mm.
As virtually only three-phase liquid starters are
involved, the electrode system consists of three
fixed electrodes and three moving electrodes.
According to the resistance ratio and the control
speed, each electrode consists of several
concentric steel cylinders for which low carbonated
steel plates are used.
The moving electrodes are connected to a
supporting bridge forming the starter star-point.
The fixed electrodes are conductively connected to
the terminals for the rotor cables.
To keep the column of the electrolyte resistance
and with that the initial resistance of all three
phases as large as possible, the electrodes are
separated by ceramic pots. When immersing the
supporting bridge, the moving electrodes mesh
with the fixed electrodes without touching,
decreasing the length of the column of the
electrolyte resistance and resulting in a smaller
final resistance.
Holes are arranged in the bottom of the electrode
separating pots such that a circulating flow of the
electrolyte is caused by thermal upthrust to rapidly
eliminate the heat from the electrode zone.
Each starter tank is provided with an earthing
connection M12 to establish a conductive connection
to the earth conductor.

Thanks for the info.

Mike

I just talked to supplier, he said the only way is to adjust the electrolyte.

Thanks everyone.

Thanks for getting back to us.

When I suggested weakening the electrolyte I'd assumed (wrongly) you were going to use the original liquid starter.

Looks like you'll have to increase it now if you want to use the old motor.