controllers

[Shaun Burgess]

hi rob . i have a small question . can i use a eurora interface with the dump set at 424vdc and your omron controller say set at 384vdc to the one dump load . is there a problem with back feed . maybe i could use diodes to stop this.. happy new year to everybody :)

[Rob Beckers]

Shaun (and everyone else), Happy New Year!

If you're talking about the Aurora Wind Interface box, it has a fixed setting of 530V DC for the dump load. Actually, you can change it a little with a few DIP-switches on the board, but only upward, so it starts at an even higher voltage (not a good idea, as it gets dangerously close to the 600V limit of the inverter!).

The Aurora Wind box can't do anything other than switch on a dump load at 530V, it won't switch off the inverter, it simply connects the dump load in parallel. So if the voltage keeps rising even with the dump load attached there is still the potential of blowing up the inverter. For that reason I don't recommend using it other than as a fancy rectifier (it's UL listed, and some inspectors insist on that).

For overvoltage protection I would stick with the Omron setup as I've published. If you need to switch on a dump load at a different voltage than where the inverter is switched off you can use a second Omron relay and contactor to do that job (though it really is a good idea in that case to use option "2" in the wiring diagram, where the same Omron relay switches the dump load on at the same time as it disconnects the inverter, since this prevents the turbine from running unloaded).

-RoB-

[Shaun Burgess]

hi rob . i agree about the interface just being a fancey rectifier. the problem is a guy here is using a hugh piggot 4.2 turbine with the interface he has solder 2 of the 10 resister together to bring the dump down to 424dc . his turbine is nearly out of control by the time he hits that. he thinking of building a omron controller say dump set at 350dc . so he thinking of using the same dump load load and have both contoller to the dump .. his idea is if the omron fails the interface is there for back up thanks sb

[Rob Beckers]

Ah, OK. That makes your question of about "back feeding" a bit clearer...

So he wants to drive a single dump load from either an Omron/contactor as well as from the Aurora Wind Box.

If both were enabled at the same time, the dump load is in essence being fed from the same source through two bridge rectifiers in parallel. For the wind box there's an IGBT in the negative lead as well, adding a few tenth of a Volt, so in all likelihood the bridge rectifier that is connected to the contactor will take the bulk of the current, and the wind box will do very little. It should work though.

I'm not sure it's worth the effort: The setup with the Omron is very, very reliable. It's hard to break an Omron relay (I've never heard from anyone that had one break), these are industrial components meant for factory automation, and even if it did, the way things are set up in my schematic, if the Omron no longer energizes the contactor it will switch to dump load anyway, adding a measure of fail-safe behavior.

-RoB-