GENERATOR BRUSHES CURRENTE DESBALANCE

[nandrade]

Hi, our Main Generator (132 Mw - Ercole Mareli 13.8 Kv) has a problem in the brushes. The collector ring has 11 brush per side. (positive and negative). We had a high desbalance with each current´s brush that causes overheating and damage. recently we buy new brushes (Alstom - OEM Generator) but our problem persist. We check the spring pression and it ok. Some brushes doesn´t carry excitation current and the other take it, making a high current difference. Some people say that could be the AVR the problem source. (Harmonics). If you know something to do or check, give me a hand.

 

[pwrengrds]

Any idea why some brushes don't carry current? Do they all have the same voltage?

Is this a recent problem or new, what changed when the problem started.

What voltage is the exciter putting out.

What type of exciter is it, static?

Are the slip rings in good condition, smooth and bright?

How much current are we talking about?

Are you using the manufactures recommended brushes?

 

[byrdj]

Suspect surface film on the brushes. Is there any change in the atmosphere around the machine? Like painting or presents of cleaning fluids.

Do you have a mandrel to contour the brush faces to ring radius? You might want to resurface brushes

If the brushes are contaminated, the ring surface too might need to be cleaned. The canvass stick works if not too bad. There are some soft abrasive stones, just don't recall brand name