Submersible Pump Starter

You may want to look at a soft start motor controller.

i am quite surprised that you are using contactors in parallel. This should never be done for motor duty, certainly not for such a high power motor. There are certainly contactors available for 190 HP and much higher power motors. Why did you have to use parallel contactors ?

Where are you located ? What is the system voltage ? Are you using DOL starting ? i am also surprised that a 750A generator cannot handle the starting surge. However, if it is unable to handle the starting current, you may need to use assisted starting. If the contactor coil is unable to hold, you may need to use a separate control supply or a battery bank.

In addition to the above comments, these previous threads and associated links may also help:

http://cr4.globalspec.com/thread/45119/Gensets-and-Chiller-Compressors

http://cr4.globalspec.com/thread/52712/RATTING-FOR-ALTERNATOR

- MS

Thanks and much appreciated your valuable reply.

We are located at Chennai and this system is for a fire water pump which runs during emergency only. The system voltage is 480V and the motor is of STAR winding and the starting through DOL. I our old system they had this two breakers in parallel with 225 amps thinking of the FLC of the motor 200amps.Being a safety system the power to the contactor coils should be inbuild from the generator out put. Pls suggest how the voltage is dropping and leads to the contactor coil chattering. We have checked the pump/motor and are free. After the starting period it draws only 190 amps of running current. Earlier this problem did'nt occur and offlate this started. Is there any thing to be checked? or if we go for a soft starter, will it work.Pls suggest.

Ok, you are using two contactors for redundancy. Good thinking. Maybe you can wire the second one for emergency use only, control-wire it up separately, even with a separate pushbutton....just a thought.

The FLC can be ~240A @ 480V, so better go for a 300A contactor or nearabout that. Some good manufacturers in India offer wide-band coils, which may be helpful here. CS Electric is one such, who can even develop special coils for you if you interest them.

You need to check with the generator manufacturer why the voltage drop is so high. Check the inrush, it may be >1500A.

You may be knowing that in USA, for fire pump motors, one is not allowed to use overload relays....makes sense to me...

A submersible pump with 190 HP (145KW) starting with DOL starter in which the actual starting amps inrush current of 1,538 Amps is required at about 3 to 4 sec during starting of the submersible pump until the submersible pump is at least 75% of the rated full speed.

With your diesel engine generator of 480v 60Hz 500kw 752amps is definitely insufficient to start the 190HP submersible pump. This is why you have voltage drop and leads to the contactor coil chattering. After starting period, the submersible pump will be running at 95% of the FLC and it draws only about 190 amps of the running current of 205 amps.

Earlier this problem didn't occur and off late this started is because they started the submersible pump with only opening the pipe valve at about 5% to 10% opening instead of 50% to 100% valve opening.

Closing the water valves will able to assist the submersible water pump motor to speed up the motor speed and reduce the inrush current time (especially for water pump). The water pumps is always carry a very heavy load as it need to pump water thru the pipe. With pipe valve opening at 50% or 100% it always cause the starting amp problem and voltage drop.

Normally for this application pump manufacturer recommends auto-transformer starting

900A starting current is not at all unusual for a DOL start of a 190HP motor (probably around 230FLA into 900A = roughly 400% current, that's actually low).

A 500kW generator should have plenty of reserve power to start a motor of that size.

Are you positive the voltage from the generator is dropping too much? It could also be that your control voltage supply transformer is too small, and combined with a slight voltage drop, is causing your chatter.

By the way, you should replace all of the contacts in those contactors now. Chattering destroys them very very quickly, they are probably already worthless.

Another possibility is that the wiring feeding the starter and this motor is on the small side. Consult a qualified local Electrical Engineer to investigate the wiring size and make recommendations.

As mentioned above, a soft-starter might be a very good solution.

From your data we observed that the starting current is nearly 4.5 times the FLC.You didn.t give the size and length of cable between the genset and starter as well as the size and length of flat cable between the motor and starter to calculate the v.d.Using two contactors in parallel is unusual,are they closing simultaneously?.You can use a suitably rated single contactor and a capacitor during the starting period. After starting you can use a smaller capacitor for PFC.Earlier they didn,t advise use of capacitors with genset but recently I read somewhere that it is permitted.If you are not sure you can get the services of a consultant. The recommended methods of starting are: DOL,shunt capacitor,Electromechanical reduced voltage,star delta,auto transformer,primary resistance or reactance,soft starter,VSD etc