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Hi, We want to use a PJ high frequency surge tester for surge testing of motors, which can give 50 surges per second upto 40 KV. We use the voltage levels for surge testing which are given in IEEE-522. The way to apply voltage is that it has to be started from 0V upto the highest voltage of...

We actually have two units of 325 MWe at our site (different plants). One of the units is working since 10 years and other has operated for 5 years. it is the older one which has problem of sparking. We have never made it a part of our maintenance routine to swap the polarity of field...

And sorry, I was unable to take photographs>[upsidedown]

As I have described earlier, the marks had appeared while generator was in operation. So, these had not appeared at stand still. My question is that if once these marks appear and cause sparking, then how can sparking vanish later while these marks were at slip ring. Look at the article at...

No, I was unable to take photographs. On negative pole slip ring, three marks were present of brush face dimensions having the spacing of carbon brushes in between them. These were also a bit spread out.

Most of the cases shown by Mersen are for motros and I had unsuccessfully tried to match these earlier. If polishing has caused sparking, then it should always spark whenever a generator starts operation after overhauling. In our case, there was no sparking at brushes at the start of operation...

Hi Everyone! Our Generator is rated at 330 MWe. Its excitation current is provided through a Permanent Magnet Generator (58 KW) and Main Exciter(1360 KW). The excitation to Main Exciter is provided by Permanent Magnet Generator using 3 carbon brushes per pole and overall 6 carbon brushes...