Just out of interest - generator question...

[flyingsparks]

Just been looking at a friends geney which he had had problems with, found the fault to be worn out brushes, but what is the rectifier for? It is a simple geny but the neutraul goes into the rectifier and back out to the 240V socket. The DC supply from the rectifier is disapperaring into the generator. No DC voltage measured when running. Thanks..

 

[ericmark]

The control of generators is normally DC there are many ways this can be done from electronic AVR's (Automatic voltage regulator) to double field windings where one with light wire is connected through rectifier in parallel to output normally with a resistor to trim open circuit voltage and another heavy winding with heavy full way rectifier in series with output again some resistor to trim in and is set to full load voltage. Also with brushless generators you get rotating diodes. Brushless is a system and the 400 megawatt generators I worked on had brushes in spite of being brushless the brushes where used to monitor the stator was water cooled and rotor hydrogen cooled may be a little bigger than one your looking at but same idea.
Eric

 

[flyingsparks]

ah right ok. Thanks ericmarc. Yep I think your 400MW geny's are a bit bigger than this one!

 

[timtheenchanter]

if its one of the cheap type of gennys, it there to smooth the 240V output.

 

[tim west]

The tap off DC is connected internally to a separate exciter winding in order to excite and increase the magnetic field and gain more efficiency to generate voltage from the AC windings.

 

[briwire]

The field of the alternator requires a steady DC voltage in order to create a stable magnetic field in which the rotating part of the generator turns. This rectifier could be what converts the AC into DC for this supply.