AVR when changing a generator from 480 to 240V

[itsmoked]

We're changing a Stadco Generator from 480 to 240.

I'm trying to understand how the AVR (SX460) recognizes the change so it doesn't try to drive the field up to get 480V.

Maybe it's handled in the generator during the re-connection? I don't understand what terminals 7 and 8 are so I'm wondering 'how do it know'?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Hi Keith. If the generator follows standard numbering, there will be 240 Volts between terminals 7 and 8.
When you reconnect for 240 Volts, Terminal 1 will be connected to terminal 7 and terminal 2 will be connected to terminal 8.
Still 240 Volts.
It should work fine still connected to terminals 7 and 8.
Look at a connection diagram for a 230:460 Volt motor. Yes it's 9 leads instead of 12 leads but 7 and 8 will be the same.
You can see that on the 460 Volt connection the voltage across 7 and 8 is 1/2 of the applied voltage.
(On a generator, the wye point is broken into leads 10, 11 and 12. The other 9 leads are numbered the same as a 9 lead motor.)

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

Or put slightly differently - in the high voltage series-connected configuration the AVR senses voltage at the mid-point of the winding and not on the line end. In the low voltage parallel connection the AVR senses the output voltage directly.

 

[itsmoked]

AHhhh! That makes sense. Pretty dang clever really. The AVR always controls to 240V.

Thanks.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Exactly Scotty. I wish that I'd said that

Bill
--------------------
"Why not the best?"
Jimmy Carter