1600KVa 11KV/415V Transformer Voltage Drop When 350KW/415v Motor Start

The main supply cable may be undersized. Of wonder is why its overcurrent protection equipment didn't operate.

http://cr4.globalspec.com/thread/83658/1600KVA-Transformer-Voltage-Drop-when-350KW-motor-start

NO Loose Connection, Cable size As per Design.

Then get the installation checked by a qualified Electrical Engineer. The sooner the better.

Note that this motor must be underloaded for a 200kVA generator to keep it running without the generator overload equipment operating.

• "We Have a 1600 KVA Transformer OLTC Kirloskar Make 11000/415vols when we start 350Kw Sq. Cag. Ind. Motor Connected with Comressor,1500rpm Voltage Drp in HT 11000 to 9800 and in LT 422v to 320. same motor same startor running smoothaly on DG 200KVA. we have connect the Capacitor 100KVAR also."

Look, something is obviously wrong here. There is no way you are "smoothaly running" a 350kW compressor from a 200kVA generator. You either have misplaced some numbers (i.e. 2000kVA generator), there is something you are not telling us, or you are making this up to be a troll.

And there is no way a correctly operating 350kW motor is causing a voltage drop on a correctly connected 1600kVA transformer unless the transformer is already severely loaded when you try to start it.

Heed PWSlack's advice, get a professional Electrical Engineer involved who KNOWS what they are talking about.

I wonder if this transformer is located near the remote end of a weak grid.

• "I wonder if this transformer is located near the remote end of a weak grid."

It could be, but that would be one extremely weak grid.

That then would come under the heading "Something he isn't telling us".

Yes, just because the OP has a 1600kVA transformer doesn't mean the utility service can actually supply 1600kVA when needed.

Quite.

Check this if you find some info

Motor Start time calculation

What type is used?. What is the rated capacity of DG-200 or 2000kVA?. What are the other loads connected during starting to transformer & DG?..

The primary system is not stiff enough to handle this magnitude of load. The fact that the system voltage drops from 11000 volts to 9800 volts is proof that it needs to be re-engineered

Beyond any doubt there is a missplaced figure in this history because the starting current could be about 5000 Amp causing the DG nearly stop the machine, no matter how fast operate the AVR and governor and on top of this, what about the DG protective devices operation, please revise your scheme again, I would like to see clarified this matter

Bye

http://cr4.globalspec.com/thread/83704

Please don't double post, it gets confusing.

So now you have cleared up one mystery, the DG is 2MVA as you posted in the duplicate thread, not 200kVA. You also say the capacitor is now 200kVAR instead of 100. Clearly one issue might be a lack of attention to details.

Just because, as you posted in the other thread (see how confusing this gets?) that you can connect a 2000A resistive load to the transformer and it is fine, does not mean there is no problem with the transformer. The high inrush current and starting current of the motor may cause a connection issue to be more immediate as the cause of a voltage drop, whereas on a resistive load it may take time to show up as a thermal issue. I would start with an infrared scan of your transformer connections looking for significant differences in temperature.

Another potential issue is the compressor itself. If it is a positive displacement compressor, such as a reciprocating or a lobe compressor, you CANNOT start it without the unload valve being open to atmosphere (or in bypass if it is a closed system like a gas compressor). If that valve is not working properly, you are attempting to start that motor with essentially a locked rotor, and if you have a newer energy efficient motor, the starting current could be as high as 700% of FLC. But that may not be the case because you say it starts on the DG, unless there is some sort of separate control issue when powered from the transformer that is causing this to happen.

A third possibility would be a problem with the Siemens Soft Starter you have (again, another detail added in the duplicate posting). but that too becomes difficult to reconcile with the fact that it starts on the DG. If anything, the soft starter might have more issues with the DG than the transformer. All clues are pointing to the transformer here, and connection issues are the prime suspect.

Rather than wasting time making triplicate threads on CR4 over a period of several days, suggesting clutching at straws, hire an Electrical Engineer immediately to investigate, report and recommend improvements to the upstream electrical supply.