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Discuss Testing an Uninterruptible Power Supply in the Electrical Testing & PAT Testing Forum area at ElectriciansForums.net

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Hi,
I'm looking for some advice on the results I got from testing a 1000VA UPS in use in a small business. With the permission of the owner I had switched-off and disconnected the PC it was intended to protect.

Firstly, it passed all tests except the differential leakage test. Is it normal for these devices to leak current via the protective conductor?

Secondly, I got a noticeable shock when I removed the mains plug from the socket and inadvertently touched the pins. Is there a legitimate explanation for this?

Thanks in advance.
 
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SparkyChick

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Not sure about the leakage, but the shock may be a result of the rectified mains smoothing capacitors in a switch mode power supply. Should have discharge resistors but if you unplug and touch fast enough they might not have discharged to a safe voltage.
 

Strima

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Sounds like a switched mode power supply and a bridge rectifier set up. You will get leakage to earth and a belt from the pins sounds like capacitor discharge.

Be very careful testing these type of items as they don't like insulation resistance tests, refer to the manufacturers guidance for testing.

Also I would recommend testing the batteries to ensure they will do their job when required, they need load testing as a shagged battery may well show good voltage but have no capacity for any load.
 
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