Windy Boy 6000 Grid inverter. Error K1 open

[Alan]

Windy Boy 6 K.w. inverter. ERROR K1 OPEN

Previous failure with K1 open was a failure of one IR2113 Hi / Lo side driver and failure of most of the out put fets.

The inverter has been working normally but has failed again with K1 open.

This time the 30 Ohm resistor  wired across the neutral ( centre relay contacts ) had gone open circuit.

I have driven both  IR2113  Hi /Lo side drivers with Pic Pwm software and the fet output stage is operational.

Any idea where to look next.

Alan

[joestue]

Really sad that they place most of the circuitry on the faith of a relay.

Am I correct in that the IR2113 is driving the output fets?

Sounds like a voltage spike of 600 volts could fry it.

Could 120VAC find it's way through that resistor?

I really can't help without a schematic though.

[laskey]

If I'm picturing that resistor in my head correctly, it's there to negate an inductive spike when the relay opens up. (like a freewheeling diode only in AC)  If it's open you may very well have spiked the FETs without blowing the driver (yet).  I would check each FET, even if you think it's good.  

When you get it working I would see if I couldn't figure something in there to protect that circuit a bit better.  Maybe a MOV, I know, sometimes they destroy themselves to save the circuit, but they're cheaper than a handful of FETs.  

[Alan]

Thanks for the replies.

My pic hardware / software drives both IR2113 Hi / Lo side fet drivers, with the output transformer

still in place. I connect a 1 K.W. tungsten lamp across the secondary as a load. And disconnect the secondary from the grid connect side for test purposes. The inverter runs as a normal inverter.

My interpretation of the 30 ohm resistor across the neutral relay contacts is that its for grid load sensing before the device connects fully ?

My intention is to not use the inverter / capacitor parts of the inverter again. Have repaired it to many times. The capacitors are 300 volt wired in series in groups of two. The P.C.B. board design has got the fet Hi / Lo driver chips very remote from the fet input stages in amongst the high voltage / current capacitor section. Very little thought went into the original design.

I was just going to use the original control C.P.U. / P.C.B. to drive a properly designed H bridge Mitsubishi I.G.B.T. out put stage with the capacitors and high voltage / current circuits remote from the  C.P.U.

Just need to get over the K1 open.