Can anyone please tell me the purposes of the slip ring and brushes that are used in an a.c. generator

Thanks

 

This is how the generator coils transfer electrical power to the outside world. Just like a motor that produces mechanical energy when electrical energy is applied to the coil, a generator produces electrical energy when its armature is rotated inside the coil/magnet structure.

 

Hi,

Strictly speaking, it's an alternator if it produces AC.

Every alternator I've seen has fixed coils and uses a magnetic field in the armature to produce the output. A magnetic field cutting across a conductor will produce a current . If the filed is fixed in magnitude, then the outout from the coils will vary with the angular velocity of the armature and the load.

That's not too handy if you want a constant voltage out, so the magnetic field is regulated by making the armature an electromagnet, and controlling the current through it. The brushes and slip rings conduct this current so the output is regulated. Unless it's a Powerguard, in which case the output is, shall we say, variable.

 

Originally posted by beenthere@Jun 5 2005, 01:19 PM
Hi,

Strictly speaking, it's an alternator if it produces AC.

Every alternator I've seen has fixed coils and uses a magnetic field in the armature to produce the output. A magnetic field cutting across a conductor will produce a current . If the filed is fixed in magnitude, then the outout from the coils will vary with the angular velocity of the armature and the load.

That's not too handy if you want a constant voltage out, so the magnetic field is regulated by making the armature an electromagnet, and controlling the current through it. The brushes and slip rings conduct this current so the output is regulated. Unless it's a Powerguard, in which case the output is, shall we say, variable.

[post=8234]Quoted post[/post]​

All of the alternator has the configuration of this. Split rings and brushes are obsolete due to brush life time. Also it adds resistance to the system. specially on high current alternators....

 

The slip rings and brushes are used to pass DC current for the field coil (on the rotor) in an alternator.

 

Originally posted by _Raven_@Jun 5 2005, 10:00 PM
All of the alternator has the configuration of this. Split rings and brushes are obsolete due to brush life time. Also it adds resistance to the system. specially on high current alternators....

[post=8241]Quoted post[/post]​

Though there are quite a few low voltage, low load, brushless alternators out there, brushes and slip rings are far from obsolete. In modern power production, the generators are still using slip rings and brushes to get the DC field into the field windings, just like beenthere and n9xv described. In the brushless models, a permanant-magnet-armature is used, and this design type is not great for high or varying loads. Most of the ones I've seen have been in home generators of less than 20KW.