Sparking Generator Brushes

There are a whole range of reasons. Here are some of the most common.

You mentioned generator, so I assume you are referring to a mechanical rectifier using a commutator and brushes and not an alternator using slip rings.

Improper rotation speed causing a misalignment of the brushes relative to the commutator segments. This is caused by the magnetic field being shifted either too little or too much relative to the correct neutral position. Fix – correct rotation speed.

Improper adjustment of the brush holder. Fix - Rotate brush holder to correct position where sparking stops or is minimized.

Short in your armature. – Fix – repair shorted or open winding on armature. This usually requires rewinding the armature on most and certainly smaller generators.

Bad connection to commutator segment. Fix – properly reconnect commutatior segment to wire.

Worn our brushes. Fix - If this is the problem, Ignore above and hire a competent service tech to fix the problem.

Brush sticking in holder. Fix – Check that brushes move freely and do not hang up.

Defective wiring / connection. Beyond the scope of a simple explanation.

Hope this helps.

Keep the brushes in well maintained condition. Other than that, try not to look at the brushes as much as possible when the generator is being operated.

There is of course poor design of the generator and if this is the case the only solution is re-design and replacement.

Assuming a DC generator the current switches direction in the armature coils as the "connections" at the commutator pass under the brushes. The magnitude of current and RPM will then determine the inductive "kick" that is generated. This usually occurs under the brush and is invisible.

You did not state the size or age of the generator. Small "toy" motors usually spark. Larger industrial machines that are well mantained and properly designed should have black commutation or only very light sparking. The overall condition of the commutator would be a key measure of successful commutation and how often the brushes need replacing.

DC Generators in Ward-Leonard or as a DC bus supply usually run at a constant speed (motors run at various speeds) and so should have the neutral point of the brushes set for its designed load and rated speed.

Rockwell (Reliance) has an excellent web page dealing with commutation and sparking.

If the collector is not perfecty round, the brushes bounce up, and spark.

Remedy : make your collector perfectly round with e.g. a lace.

paulvandenbossche@monti.be

What causes sparking at the brushes of a generator and what are the remedies?

I have worked on many generators and have found after the generator has all the brushes and commentor checked, repaired, cleaned and wire connections ckecked out, and still sparked it is time to call a millwright. The problem can be bad bearings, bad coupling, coupling misalignment soft foot, looseness, missing or loose bolts, also check for rotor imbalanced. Laser alignment is the best way to align the unit be it on a small MG set or a big MG set with 5 inline gererators to 250 ton Cranes on Rails. The vibrations can be either harmonic or resonating it don't make no difference at 1800 or 3600 rpm it will cause brushes to vibrate causing the sparking. The sparking can cause some electronic control systems to shutdown. For small gas power generators take them to lawn mower shop for repairs.

In all these Blogs on CR4, this is the first one that I have read that has had 'perfect & spot-on correct' infos from first to last. Well done Gentlemen! It was pleasure to read.

But you have left basically nothing over for the rest of us to write!! Snivell, snivell!!(how does one spell Snivell???)

Iron Man gave you all the correct symptoms and remedies. See his posting. I would only like to add the "WHY" it happens: A spark happens when an electrical circuit is opened or closed and it has to do with the process of equalizing energy levels. The spark will always starts at the higher potential point and will subsides once both electrodes reach same energetic levels. On a brush motor it usually happens when the brush touches two commutator segments at the same time, one energized and one not. A spark is very high energy content and in the long run will ruin you electrodes (arc welding) hope it helps

Wangito.