Uninterruptble Power Supply (UPS) Fail/ Faulty...

Discussion in 'General Electronics Chat' started by kengloong, Dec 7, 2005.

  1. kengloong

    Thread Starter New Member

    Dec 5, 2005
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    0
    Anyone can give me some idea on what's possibility Part Fail/ Faulty if the UPS doesn't give any output voltage during it's run on battery?

    I wonder why I already replaced 4pcs Power MOSFET and the Voltage regulator IC but the system still fail.

    For your information, during the UPS run on battery, it's indicated the UPS failed and doesn't give output voltage. So, when I switched on the UPS again (Switched on the Incoming Supply). The relay doesn't working to cut off the supply from a battery after the supply take over by commericial AC supply.

    The Power MOSFET original part number is STP60NF06, but unfortunately I can't get it, so I replaced it using STP60N06. Same to Voltage Regulator IC, I replaced LM317 instead of original part number is LM317T. Is it will affected the system?

    Hope someone can give me an idea how to solve my problem.

    Thanks!
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    The battery is often bad when a UPS won't pick up the load. If the charger circuit lets the float voltage go too high, then the battery will overcharge. It will either dry out, or a cell will open. The battery may look good to a voltmeter, but the voltage will fall immediately to near zero when a load is applied.

    Your transfer circuit might also be bad - something has to start up the inverter and switch to it when power fails.

    When checking power mosfets - look for the intrinsic diode. You should see the junction when checking from source to drain - the diode will have its cathode to the drain. All other checks should be open. They tend to short out, rather than open up.
     
  3. kengloong

    Thread Starter New Member

    Dec 5, 2005
    4
    0
    For your information, the battery I already replaced but still no supply to the output.

    Any possibility because of I replaced the Power MOSFET original part number is from STP60NF06 to STP60N06. Same to Voltage Regulator IC, I replaced LM317 instead of original part number is LM317T. Is it will affected the system?

    Hope to hear form you soon.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    As far as I can tell, the substituted parts should work as well as the originals.

    Without a schematic of the UPS circuit, it is very hard to determine where the problem is.
     
  5. kengloong

    Thread Starter New Member

    Dec 5, 2005
    4
    0
    My UPS now is working only after I replaced the Power MOSFET STP6NF06. Now I faced another problem that is when my UPS on standby, it's able to supply 240VAC in output.

    When I switched off the incoming supply, the UPS's battery backup able to backup 240VAC without any load. When I switched on my computer, it's backup only for few seconds. Why this was happen?

    Hope someone could help.
     
  6. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,280
    1,072
    Do the following:

    Plug the UPS in and let it charge the battery overnight. Measure the charging voltage ... probably close to 13.7 volts per 12 volt battery [approx 2.2 volts per cell].

    Obtain a incandencent lamp of about the same wattage as your UPS. If need be, place a few lamps in parallel until you achieve the required wattage.

    Using the lamps as a load, connect a voltmeter across your battery pack.

    Unplug the UPS from raw mains and see what the voltmeter reads as the lamps are energized.

    If the battery voltage drops suddenly the battery could be defective or not charged properly.

    Worse case scenario ... disconnect your battery(s) and charge them individually with an external charger. You can connect a resistive load across each battery and measure the battery voltage under load. The resistive load can be a heating element or any low ohm high wattage resistor.

    Once you ensure your batteries are up to snuff, you can install them back into the ups and begin testing again. Start with a light load [100 w bulb] and make sure it runs an appropriate time.

    Good luck.
     
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