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APC BACK-UPS transformer


autir
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Hello all
I have two UPSs from APC. One is model APC Back-Ups 400 and the other is APC Back-Ups 600. Inside each box there is the PCB, the battery and a big heavy transformer. Can anyone give me details regarding what type of transformer this is? I have downloaded the service manuals but could not understand which transformer it was.

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Hello :D

This is the main power transformer that steps up the low AC voltage to a higher level AC volatge (110VAC or 220VAC). This has usually a ratio 1:10 between primary and secondary windings and can be used also as a step down tranformer if you use it in reverse.

How many terminals can you see on this tranformer?

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Six. Three on one side and three on the other. The AC voltage of the devices in my country is 220-230V, if that helps. Are the two transformers - the one from the backups 400 and the one from backups 600 - the same? How many Amperes can it support? And how do I measure it?

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Inplug it from the rest of the circuit and mark the side used as secondary (the side that goes to outlet and gives 220VAC). Then with a multimeter measure across the terminals of each side to find the two separate coils (use contiunity tester). Your transformer will look like the one in the image below. It must be T2 in schematic (....-sxems.pdf). Then short the two terminals so you have one coil each side of the transformer and two free terminals. Then with EXTREME CARE apply 220 AC on the secondary winding and measure the voltage on the primary.

Then you can find the ratio dividing the two voltages 220/what you measure on primary. The most possible rating of your transformer is 2x120VAC on secondary and 2x12VAC on primary so you must measure 24VAC on primary (when you short the coils).

The power of it must be at least 400VA on the one and 600VA on the other. Check the size of each transformer if are identical. If they are the same then they are 600VA both of them otherwise the bigger -> the most powerfull, .

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