Switching field supply

[bobansen]

A question for you boffins. I now have two units ready to supply the house, 195 @7.5kw + 1115 @10kw. but need a kiss proof method of isolation between the heads. I will use two contactors. ie one for each head being energised by the voltage coming from the head. QUESTION! can I use the field to switch the supply to the contactor. that is open field ,no voltage to the coil. Each contactor will be linked through a NC so when head (A) is energised, the field of (B) will be open curcuit and visa versa. B in (A) will be open circuit. Does anyone see a problem that has not come to my mind. I have yet to do any wild trials so will wait untill some one shouts "NO...Dont do that because"...
I plan to photo some of the stores here so the group can see what is ready available in regards to engines. I suggest members state side get a box of tissues so you can hide the tears. EPA has no meaning here, but maybe (Every Plonker Available).
Tks in advance
Bobbie

[Ronmar]

If you start siphoning off energy from the field to drive your control circuitry, you may alter the field characteristics and the output of the generator.  Cross linking the contactors like you mentioned, coil of A's main contactor being fed thru an aux contact on B's main contactor, so B must be de-energized/open before A can be put on line and vis versa should be sufficient.  No need to mess with the fields that I can see, and way more KISS IMO.

Good Luck 

[bobansen]

Hi Ronmar,tks for reply so fast. Following your suggestion the two were wired for a dummy run. Great!  Start (A) and it goes on line. Start (B) and it sits on standby ie contactor out. Off (A) and (B) comes on line. At least now I can allow the engine to get up to temp before throwing a load at it.
I am sitting with a smile feeling very smug!!!
Tks again B