4500kW 13.8kV Motor DOL Starting

Are you trying to start this motor without a proper starter?
Are you out of your mind?

The starting current will trip a lot of overload/overcurrent relays . . .

Dear Respected Gurus/friends

I mentioned the name of the software to ensure that I used a widely popular and valid means of calculation than doing my own spread sheet. I do have ans of the Q, but placed in the forum as a topic of discussion, where people write to share knowledge. There is no question of payment for reciprocating knowledge what I understand. I am a quite old communicator(as well as age and experience) in this forum and wrote many replies to share my experience and views and never wrote any words of payment etc. I understand its voluntary in the forum to write.

Ok, now coming to the topic, The auto transformer, reactor are the options. I got a good reply like to check the inertia of load, motor, coupling. Yes, we can use hydrolic couplings to enhance the accleration situation. This option can be thought of. The last resort is soft starter, is known to everyone.

Using capacitor during starting will not enhance the voltage drop situation also it will unnecessary increase the complication of the circuitry as correctly said.

Thanks to all for the time and replies.

4.5 MW motor started in DOL mode ? Has it any time started before ?

My humble opinion is , it would never .... without affecting the bus .

Best is to start with an Auto transformer , at the right speed pick up , bring in the DOL switchgear in line. The autotransformer does it job only at the time of start and is totally maintenance free static unit . But you may need additional two switchgear units - one to put Autotransformer in line and another to make its windings ' STAR ' . This is only at the time of starting .

Can I assume, that the mechanical load with its unspecified inertia, and braking load is not connected during this startup? I see it not even mentioned. Curious, or I miss something. Current drawn and voltage dip should be heavily dependent on it.

what is the load? capacitors won't help.You have to size the transformer so that drop is within limits.Such a large motor needs a study of load Torque curve superposed on motor torque vs speed curve.Normally most motors can accelerate a load to rated speed with 80% of the rated voltage at motor terminals for soft load like a centrifugal pump.large inertia drives mandate a detailed study.What is the rated speed, method of coupling the motor etc need to be informed to suggest a suitable solution.Pl see similar threads in this forum.