Hi All,
I have an APC Back-UPS 650 (400W) UPS that works great as an inverter, but has stopped functioning as a UPS. The fact that it functions as an inverter leads me to believe that all the 12V circuits, and the inverter circuitry, is fine and functioning well and (hopefully) not part of the problem.
However, unit cannot be plugged into the wall power without blowing fuse F3.
I've traced this as far as finding a 1-ohm load placed across the neutral and hot of the power cord when F3 is in place. The primary winding of both the inverter transformer and battery charging transformer, coincidentally, are both 1-ohm loads. I *think* that somehow this load is being transferred to the hot & neutral on the power cord, but cannot see how.
Nothing looks bad or blown on the board.
I consider myself at hobbyist/student level, some formal training, some work experience, but not familiar enough with UPS to understand why the 1-ohm load is present across the hot & neutral of the utility power cord.
I've checked the main relay that swaps power over, but it seems to be working fine.
Does anybody have any ideas? Anybody familiar enough with UPS design to maybe bump me in the right direction?
All help/guidance appreciated.
Thank you for being here,
Bud
I have an APC Back-UPS 650 (400W) UPS that works great as an inverter, but has stopped functioning as a UPS. The fact that it functions as an inverter leads me to believe that all the 12V circuits, and the inverter circuitry, is fine and functioning well and (hopefully) not part of the problem.
However, unit cannot be plugged into the wall power without blowing fuse F3.
I've traced this as far as finding a 1-ohm load placed across the neutral and hot of the power cord when F3 is in place. The primary winding of both the inverter transformer and battery charging transformer, coincidentally, are both 1-ohm loads. I *think* that somehow this load is being transferred to the hot & neutral on the power cord, but cannot see how.
Nothing looks bad or blown on the board.
I consider myself at hobbyist/student level, some formal training, some work experience, but not familiar enough with UPS to understand why the 1-ohm load is present across the hot & neutral of the utility power cord.
I've checked the main relay that swaps power over, but it seems to be working fine.
Does anybody have any ideas? Anybody familiar enough with UPS design to maybe bump me in the right direction?
All help/guidance appreciated.
Thank you for being here,
Bud