Info on weird current transformer

Jun 15, 2006 2 Replies
N

Hi, i am currently analyzing a three phase compounding CT, used in a generator field excitation system. It is very unlike normal metering CT, which is basically a coil around a big conductor, this thing consists of thick copper primary coil and 2 secondary coils on each side of the primary, wrapped around a big laminated iron core. There are three primary turns and 16&3 secondary turns. The primary turns are connected at the neutral side of the generator.



Has anyone got some info (or maybe patents) on this kinds of CT's? Help will be appreciated.


http:/members.home.nl/damellema/ct_front.JPG http:/members.home.nl/damellema/ct_top.JPG http:/members.home.nl/damellema/ct_bottom.JPG



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P

I have seen a lot of high current components, but this is a new one for me. It looks similar to a paralleling choke (or transformer) used to compensate for slightly different voltages from variable transformers. The number of turns indicates that it has a working voltage of only one or two volts at

50/60 Hz. It may be an interphase transformer, which I saw once on a huge three phase DC test set that was rated at 30,000 amperes at about 15 VDC. I think the purpose was to balance the voltages to the rectifiers for a smoother waveform. A schematic of the generator system might be helpful, but I am not an expert in generators. Good luck.

Paul

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G

Looks like its purpose is to increase generator excitation as load increases by directly supplying power to the exciter proportional to total generator current:

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I don't think this method is widely used in new designs today.

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