Continue to Site

Welcome to

Welcome to our site! is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

i have powerware PW9120 3kva having problem 'low voltage output"

Not open for further replies.


Member level 3
Jan 28, 2013
Reaction score
Trophy points
Activity points
any body encounter same issue with me? on the display say's Low O/V fault, i also check the output voltage its 0V,
all battery are good.

thanks in advance..

DC bus is bad.
**broken link removed** But in Russian and PW6000
i already replaced the dc bus,,but still no lack..,:-( i try to figure out the pcb mark as they mention in that forum but i cant find it.
Actually the first problem with this unit was Charger Failed or sometimes the it show up Utility failed after we do some replacement of component it worsen now the problem is low o/p voltage... :-(

I also can not yet find a complete circuit, there is only functional. Error "Low O / V fault" may be caused by low voltage DC. You measured the voltage DC + and DC-? They are the same? Try running on battery power, check the operation of the inverter and the DC/DC converter.
**broken link removed**
Last edited:
thanks for the link, its very helpful even its not english :) later i give you a feedback once i check the inverter and dc/cd converter...

i found out, that out of 4 IGBT 2 of them having low voltage reading around 203V and the other 2 IGBT around 236V. I need to isolate this igbt to confirm if this is the one causing the low o/p voltage.

Re: i have powerware PW9120 3kva having problem 'low voltage output"

I was a little reworked scheme from the site. Designate certain components may be a mistake. Try!

- - - Updated - - -

Ideology of the work of UPS:
1.When the network /even without battery/
Starts to work on the charger with Q2 .generates approximately 105-110B.
From this is powered by and starts to operate additional info source. The fan is spinning.
Turns on the display.
2.When you click 'Start' begins to operate the booster on the Q11-Q14, Q24, Q25,
From the battery voltage creates a voltage 380,- 380B. The average point neutral and ' -' battey/
Charged with15-С18./ not swollen?/
respectively, without battery UPS will not turn on.

3.Optocouplers are with the network frequency on transistors Q5, Q6 and Q7,
Q8 are fed bursts /50 Hz, it must obtain!/ RF pulses.
After throttle and capacitor /L2-L4 and C25/ is a sine wave.
4.Turn on relay RY1,
Through the fuse F1 network is supplied to the catwalk REC2/check,
Is not pierced whether !/ and Q15
they produce offering only -38of to charge capacitors.

4.1 The case check chain D29-D32, chip U12.
Check continuity between the feet 2-3 /should be 40-50k/ and 5-6 /2-5 MOhM/
5.If all OK,
OOPS goes on line
1. What is the voltage at the battery / black socket accessory rear-5 has.
The top two' - ', the lower ' '/ There is at least 90 volts?
/Norm105-110/ 2.
When the voltage at the battery increases/i.e. Charger works/?

3. Remove the network and try to include UPS from the battery. Come on? The display on battery?
If turned on,
You can with the certainty that a chain is damaged power adjustment,
i.e. ,
Power elements : relief.F1, bridge REC2 , the transistor Q15 and
complex acoustical elements : diodes (D29-D32 - 1N4148,
A chip U12 -1C358, оптрон U13 - TLP250, the diode D35 -1N4148, resistor R117- 22om, R118 - 47om
This is a translation, I'm sorry for the mistakes, fix no time.
Re: i have powerware PW9120 3kva having problem 'low voltage output"

thanks for the effort...very appreciated :), i'll try this one...

I measured the DC+ and DC- the reading around 390VDC but the figure was keep on dropping. and also no voltage reading on C25 10uF 350Vac. :-(

Are there pulses on PWM- and PWM+, inputs and outputs U4 and U5, gates Q5 Q6 Q7 Q8 ? Work carefully there is high voltage.

Not open for further replies.

Part and Inventory Search

Welcome to