Surge Capacitor


Thread Starter


Hi All,

What is the purpose of surge capacitor at motor terminal in high voltage motor? We have one 4.16KV 1000HP motor with surge capacitor at its terminal. We suspect this capacitor is faulty. Switchgear tripping on instantaneous current when starting the motor. Meggering cable, motor found OK. Capacitor phase to ground resistance showing 500kohms. Part number of capacitor is 18L15UJ. make: GE.

Can anyone advise whether we can try starting motor without this capacitor to prove motor is OK.

Never heard of a motor surge capacitor. Most likely a power factor correction capacitor [bank]. Motor can be started without the capacitor, assuming it's a 3 phase motor. I've not heard of or seen a high HP motor that wasn't.
thanks for the reply. It means that we can try starting 4.16KV, 1000hp motor without this surge capacitor? There is no potential risk of arcing or flashing? There is no KVAR given (no value given in KAVR column) as per name plate of the capacitor. It is rated for 1.5mfd. Diagram inside motor terminal shows a capacitor and a resistor in parallel.
Your follow-up statements have rendered me uncertain at this point. Can you take pictures of the nameplate and diagram, upload to cloud, then post a link to them here?
Links take me to Dropbox sign up page. I'm not going to sign up just to view the photos. Please find another way...
Where's the diagram? No problem without, however. I believe I found a copy of the motor application manual online at:

The capacitor you refer to is, in fact, a surge capacitor. The manual has only a small blurb about the concept on page 293 of 416... but nothing in the way of detail.

As best I can tell, the motor can be started without it.