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bahadur08
Joined: 17 Aug 2008
Posts: 5
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 17 Aug 2008 6:22 How to correct output voltage of a UPS? |
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Hi, I have a Taiwan made Generic Line Interactive UPS 1000VA. While changing battery, accidentally the negative cord of the battery touched the metal body. As a result, two transistor (C1815) just burnt out. On the other side of PCB, a tiny 3 leg black color parts ( May be a transistor, I don't know what it is) and one 2 leg mini register like parts also burnt out.
From used goods market I have just bought another same board. I have found that one capacitor is dry soldered. After re-soldering, I have given it power and battery connection. Battery is charging fine, in AC mode the output is 222V. When I switch off the AC line it goes on inverter mode but the output is 152.
At the end of the day, I have two same UPS board. One has no output Voltage and other has low output voltage.
Could anyone please guide me how to solve this problem.
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Awarapunshee
Joined: 11 Jul 2007
Posts: 338
Helped: 45
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| 17 Aug 2008 6:58 Re: How to correct output voltage of a UPS? |
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| Connect some load and see if output increases or not. Because some design is like that, without load 188V AC but load is connected output become 200 or above.
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bahadur08
Joined: 17 Aug 2008
Posts: 5
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| 17 Aug 2008 10:09 Re: How to correct output voltage of a UPS? |
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So far I remember, before the burnt out this UPS gave 235V output voltage at inverter mode without any load.
Well, I will take your advice and I will add some load.
Let's see what happens.
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bahadur08
Joined: 17 Aug 2008
Posts: 5
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| 18 Aug 2008 2:56 How to correct output voltage of a UPS? |
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| After giving some load, still there no significant output voltage increase. Now output voltage is 164.
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Awarapunshee
Joined: 11 Jul 2007
Posts: 338
Helped: 45
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| 18 Aug 2008 5:02 Re: How to correct output voltage of a UPS? |
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| bahadur08 wrote: |
| After giving some load, still there no significant output voltage increase. Now output voltage is 164. |
Which means output increases, although not as we need. Now try to locate the feedback path and if there is any variable resistor to adjust and also make the load double and see the output.
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bahadur08
Joined: 17 Aug 2008
Posts: 5
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| 22 Aug 2008 13:17 How to correct output voltage of a UPS? |
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I have installed UPS monitoring software such as Commander Pro and WinPower with a P4 PC with 15 inch old color monitor with 1.4A current drain. These softwares give real time measurements of loads, input and output voltage along with battery capacity.
This is quiet interesting that those softwares are showing output voltage is 230V though a high quality digital multimeter is showing 187V output.
Added after 7 minutes:
There is no variable in the whole PCB. How can I change the voltage?
Other symptom arises, the UPS gets power off after running 6 minutes though battery has enough charge.
I tested many times and it shows that some kind of timer has activate out of nowhere.
Any help?
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rajudp
Joined: 27 May 2006
Posts: 120
Helped: 4
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| 23 Aug 2008 13:40 How to correct output voltage of a UPS? |
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| Try Check both side switching mosfet conntected to transformer. if it is fine check the pwm is getting yo the mosfet
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blackheart
Joined: 01 Sep 2008
Posts: 1
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| 02 Sep 2008 1:31 Re: How to correct output voltage of a UPS? |
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This coule be a waveshape issue. Many multimeters will only give the proper value on a sinusoidal signal. The further the signal is from a sine wave, the larger the error. Do you know what the waveform of your UPS looks like?
Blackheart
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