Repair of Power Master inverter

[frackers]

Greetings all

I'm trying to repair a Power Master pure sine inverter for a mate http://www.powermaster.com.tw/PM-6000L.htm but not getting any joy from the manufacturer with schematics etc. I was wondering if anyone has ever worked on one of these and can help diagnose the problem.

For some months the inverter had been very quick to report over-temperature (even though it is running cool)  but now it seems to power up in this error condition.

I've checked all 4 temperature sensors, they all show the same value so I guess they are OK. Having no idea how they interface to the micro controlling the whole system I'm now a bit stuck!! Due to the gradual decline, I would guess a bad capacitor somewhere or deteriorating reference supply but rather than changing everything on the control board I'd prefer to tackle it in a more logical fashion - if only I can get some basic info for it!!

Last resort will be tracing out the power PCBs to work out how to interface an EGS002 board

[oztules]

Can't help with the circuit... but think you need to follow the tracks from the sensors to the micro... find the pin that is toggled, and put an opposite sign on it and see what happens. It may go to quad compactor first , who knows, but eventually goes to the micro.

Failing that... you have transformer and fets and 002 board.... it will work one way or another.

Just had a little 24v 5kw pj come back from the north of the island..... water and control card don't mix apparently, so eg8010 to the rescue!.... gee they have changed my world.... never scared anymore.... if there is a box and transformer, the rest is a soda.



...........oztules

[frackers]

Making some progress on this. Got all the schematics (apart from the CPU board) from the manufacturer after the reseller redirected my query. Some interesting circuit features!

Each leg of the H bridge has 18 IRF3205 in parallel (this is a 24v inverter) that are driven in 4 blocks of 4 & 5 from complementary bipolar transistors all coming off a common opto. Gate voltage comes from separate windings for high and low side on a DC/DC converter using a UC3845 chip and a MOSFET driver. The toroid primary is 8 in hand which terminate individually on the heatsinks for the low side drivers. The 4 heatsinks are arranged side by side with the low side (primary connections) on the outside and high side on the inner, the fan blows down the length of all of them. Two 300A fuses in parallel on the low side board 'protect' everything.

Multiple NTC temperature sensors are individually buffered by an op-amp and then diode NOR'ed together to provide a single temperature monitor feed back to the CPU.

Found a few dry joints, lots of dead moths etc and now reassembled ready for testing tonight after a thorough clean with IPA and a stiff brush!!