Inverter trouble

[(unknown)]

I have recently bought a secondhand Trace/Xantrex inverter/charger. The model name is UX1112 E SB, which mean 220 volt 50Hz, 1100 watt inverter with 50 amp 12 volt charger and transfer relay.

The unit is working properly as an inverter but there seems to be some problems with the transfer relay. The relay does not switch to charger/transfer status when 220 volt is applied to the AC input terminal. I can't hear any clicking sound from the relay either when the 220 volt is applied.

I'm grateful for any advice regarding solving this defect

Aurora

[wpowokal]

Not familuar with Trace gear but basic fault finding may help, check all internal fuses as a starting point.

allam down under

[boB]

No fuses in the UXxx12 series of inverters but seem to remember a small

circuit breaker you might check.

Going a bit deeper, there should be an 18 pin IC near the charger

end of the PCB.  Maybe in an IC socket.  If it's in an IC socket, make sure it's

pushed in all the way and didn't fall out partially during shipping.

The microprocessor drives a transistor that in turn enables the 12 Volt

coil of the relay.  You could look with a meter or scope across the relay

coil and/or the drive transistor from the micro.  Should be a single resistor

from the micro to the relay drive transistor.  The relay is a  big Deltrol relay.

Another thing to look for is a signal from the AC line input which drives a

small transformer, the secondary of which (low voltage) goes into the A/D

converter in the microprocessor.  The A/D input sees the whole AC input

cycle from the secondary and has a 2.5 Volts DC bias at the A/D input.

Capacitively coupled with another series resistor.  If there is no AC

swing at the input of the micros A/D converter pin, but there is 2.5 Volts

DC at that pin, the little transformer ~might~ have an open winding.

The micro must see at least so many volts of swing and can't be too far

off in frequency, but does have quite a good range as I remember. (It's

been many years now)

This might be totally off, but hopefully helps a teeny bit.

boB

K7IQ

[(unknown)]

Thanks for the input!

After reading boB's post I did a carefully examination of the PCB and the components. On what I belive to be the charger "part" of the PCB I found one blown capacitor. You can se it to the left on the image.

Is it likely that replacing this capacitor will solv the problem, or is this just an indication of that something is wrong with the circuit?.

I also tested the relay by applying 12 volt on the coil. The relay made "normal" clicking sound and transfered the AC from the in to out terminal.

Thanks,

Aurora

[boB]

Ouch !  Was that a little non-polarized capacitor at the end of that IC ?  The LM339 ?

That would be unusual I would say.  I ~think~ that capacitor is just a bypass

capacitor.  Hook up the battery and measure the DC voltage across the two

wires that the capacitor left standing there and report back the voltage if

you could.  It ~LOOKS~ as though the capacitor was overvoltaged maybe.

If you measure somewhere near battery voltage there (10 to 18 or so volts)

I would just try running the inverter/charger like normal again.

Maybe the capacitor was just shorted and has now opened up

Just a guess.

Yes, energizing the relay as you did would pass through AC.  At least the

relay is good.

boB

[(unknown)]

Yes, it is the LM339. Before I read your last post I replaced the capacitor with a new one with similar ratings. So far the the replacement did not change anything.

After hooking up the battery I measured 10.78 volt across the new capacitor. Battery voltage was 11.6 volt (nicad, pocket plate). I also tried to activate the relay to check if the charging ciruit was operating after the capacitor swap but nothing was changed.

Thanks,

Aurora

[boB]

OK... So the internal power supply is OK I guess.  Battery voltage minus a

diode drop or two...

Now, if the unit still inverts (I think you said it inverted OK), time

to check some other stuff in the charger circuit.  Towards the AC input

and AC output, is there an 18 pin IC there ?  Microchip 16C71 ??

When AC input is applied, that chip has to see that as well as the

DC battery voltage because it is regulating the charging.  The 16C71

drives an 8 or 6 pin white (think it's white, opto) IC that in turn

drives that big round triac that does the charging.  Triac should be mounted

to the end of chassis as I remember.

I think you said that the relay is not engaging on its own though so the

next thing I would look at is the little transformer that takes the 220VAC

in and steps it down so the micro can tell what's going on.

I ~think~ it might even be that transformer in the right hand side

of the picture you posted.

There is another transformer about that size with one or two turns

of wire which is the current sense transformer.  That tells the charger

when to limit the current so you don't blow the breaker etc...

boB