Circuit Problems

Maybe I can help you to analysis whats wrong with it. pls show me the circuit diagram at info@ndt.cn

what chip do the set use?

check fuse at first and no short in the circuit.

A couple of questions:

How old is the unit? Does it have any large electrolytic caps that may have dried out and changed value? What does the initial inrush current look like? Does it have any indicators (LEDs, Beeper, etc.) to give error codes? Does it have an RS232 port for analysis. Does it shut down completely after one second or does 230vac only stop? For that matter, does 230vac ever actually come up at all?

A pure sine wave inverter must either have a true sine wave oscillator and a frequency standard or they may have fibbed to you and it actually uses some kind of SCR or flip flop circuitry to generate a mostly square wave which is subsequently heavily filtered to approximate a sine wave.

A large toroidal transformer will probably be indicative of a filtering output circuit. The big caps also. If it has a crystal freq reference that will probably be temperature compensated.

Fault conditions that would shut it down will include excess current (possibly caused by a short in the output circuitry), over temp (any big transistors or SCRs--remember that big power devices are sometimes difficult to test accurately), and off-frequency. There will have to be sensing for these faults built in there somewhere.

You might try bringing it up on 12vdc input for 120vac output with no load on the output. If it will run at all, that probably indicates an OK output/filter circuit.

Don't know if any of that might help--I'm pretty ignorant about power inverters, but they all have to take DC, chop it into pulses, transform it to higher voltage, and filter it into acceptable AC, and protect themselves while operating.

Good luck.

Though there are different reasons for failure,following step can help.

If you are operating several loads from the power inverter, turn them on separately after the inverter has been turned on. This will ensure that the power inverter does not have to deliver the starting currents for all the loads at once.

Check the voltage at the input terminals of the power inverter. At low input current, this voltage is very close to the battery voltage. At high input current, this voltage will be lower than the battery voltage because of the voltage drop across the cable and connections.

Ideally, the voltage should remain within the permissible range given in the 'bar' graph. Otherwise inverter may shutdown.

Hi, you did not say whether the inverter was under load when you turned it on. It might matter. What size battery bank are you operating off of? My inverter will shut down if input voltage drops below 11v. on a 12v system.

I have enough experience with inverters and UPS systems and the problem you describe is quite standard in inverters.

First thing you must check is the battery pack for defected batteries.

Then the battery charging section must be inspected.

Ahhh Powertech inverters. I had so many issues with the 500W version (including blowing it up) that I sent it back to the supplier (Jaycar over here in NZ and Aus). My problems came about because I was trying to drive four standard 4 foot 36W fluorscent lights. The power factor correction capacitors across the phase and neutral were killing the inverter (it is still a chopped output waveform afterall). It shut down a few times, killed the fan motor circuit then blew up and let the smoke out. The replacement didn't fare much better. I replaced it with a "true" pure sine wave inverter (more expensive) from a local manufacturer and it worked fine. It just goes to show you that "Pure Sine Wave" does not necessarly mean "True Sine Wave". Don't believe everything you read!

It does sound like inrush current overload causing inverter shutdown. What load are you trying to drive, and are there any big capacitors across phase and neutral?

Also, check both your batteries when they are under some load (we had a similar 24V system keep dying because one of the batteries was dead, but still showed 11V when no load was connected, but about 5V when loaded up).

Jack

Thank you for the good real world info--this thread helps me see that I'm not the only one to ever have a battle with a "sine wave" inverter. Fried an audio amp that didn't like all the excess harmonic content. I was thinking of the caps as "filtering" but PF correction is probably a lot more accurate.

different topic for a moment. What is the armored vehicle in your little picture? Looks too squat for an M48 series--can't see any troop rails for a T62--looks a lot like a Chinese T55...in NZ?

Lonnie

i am sharing my experience with battery .when you check a battery dont go by voltmeter readings .it will show 12V with out load and dead when connected to load.please check the dencity or (specific gravity with a specfic gravity meter)of the electrolite if its a new battery it will be in the range of 1270 if the dencity is 1200 or less charge the battery if the dencity falls rapedly and takes very short time to attain 1250 or 1260 then your battery is deying and require replacement.this is additional information on battery i have gathered over a period of 20 years.Hope it might help

It's actually a Centurion tank I hired out for the morning for a drive around a forest from a business called "Tanks for the memories" down in Christchurch. Lots of fun. Turned up in the morning and who should I run into but an Australian tourist who drove Centurians in the war (and has his own one back on the farm in Aus). It really is a small world.

No, the main gun was disabled.