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Any knowledge of this UPS: CPS 1500AVR

Hi,

I have here a CyberPowerSystems 1500VA (950W) UPS which has failed in a mos t peculiar way. Actually, it's not the failure that seems peculiar to me, b ut that it was ever designed this way to begin with. I've chosen not to mov e forward with any replacement parts until I can nail down exactly why they are there and what kind of intoxicants the original engineer was on at the time of design.

First off, it doesn't know what model it is. The front says 1500AVR, the st icker in the microcontroller says OP1500 (which is another CPS model), the board says OP2200A (yet another). Ignoring that...

There are two large transformers, completely parallel with each other, each with three windings, two with taps. Of interest is the non-tapped winding, which gives me 24V, and connects back to the main board. It hits first a 6 .3A fuse, then a full-wave rectifier (made of discrete diodes), expected fi lter cap, and then... a mosfet. a 60V 80A n-channel mosfet. Source and drai n. The gate goes back to a collection of surface-mount parts which my eyeba lls can't seem to follow.

I can't see any reason for this mosfet OTHER than to blow that fuse (which is exactly what it did. the mosfet is failed short).

Anybody have any familiarity with these? I've read that they're not very re liable, they must fail fairly often... so I can't be the only person with a broken one...

Reply to
microg33k
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Am I correct in understanding that your question is... Did the MOSFET fail of its own accord, or is there something else kaput that's likely to take out the replacement?

Reply to
William Sommerwerck

Not the same model, but I have a PowerCOM PCM "Black Knight" 500VA that I roughly traced the circuit of.

Similar, but the "fuse" seems to be a 0.1R resistor, bridge, then an FET right across the supply feeding onward to the battery charger section.

Your posting reminds me of the same puzzlement I had. On mine, a pin on the MicroController operates an intermediate transistor that feeds the FET, and seems to be an emergency shutdown to forcibly stop the charger dead.

Some kind of controlled crowbar. Or a "warranty expired, time to replace me" timer :)

--
--------------------------------------+------------------------------------ 
Mike Brown: mjb[-at-]signal11.org.uk  |    http://www.signal11.org.uk 

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Reply to
Mike

Den 09-05-2013 22:12, Mike skrev:

Crowbar is the correct term. Here is an explanation of the function:

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Uffe
Reply to
Uffe Bærentsen

Den 09-05-2013 20:55, snipped-for-privacy@yahoo.com skrev:

peculiar way. Actually, it's not the failure that seems peculiar to me, but that it was ever designed this way to begin with. I've chosen not to move forward with any replacement parts until I can nail down exactly why they are there and what kind of intoxicants the original engineer was on at the time of design.

sticker in the microcontroller says OP1500 (which is another CPS model), the board says OP2200A (yet another). Ignoring that...

with three windings, two with taps. Of interest is the non-tapped winding, which gives me 24V, and connects back to the main board. It hits first a 6.3A fuse, then a full-wave rectifier (made of discrete diodes), expected filter cap, and then... a mosfet. a 60V 80A n-channel mosfet. Source and drain. The gate goes back to a collection of surface-mount parts which my eyeballs can't seem to follow.

exactly what it did. the mosfet is failed short).

reliable, they must fail fairly often... so I can't be the only person with a broken one...

Crowbar circuit. Found on Wiki:

formatting link 

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Uffe
Reply to
Uffe Bærentsen

It just seems unusual for the crowbar to be operated by a microcontroller I/O pin. Normally, it would be a zener or voltage reference, so that if supply voltages were exceeded it forcibly held things down until something went pop. A standalone safety circuit.

And this is stopping off the *input* to a current limited, voltage regulated lead-acid charger designed for 12v 7-9Ah batteries.

--
--------------------------------------+------------------------------------ 
Mike Brown: mjb[-at-]signal11.org.uk  |    http://www.signal11.org.uk 

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Reply to
Mike

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