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I have a 220 V to 110 V transformer but it's not the type which comes with the plug and outlet built-in so I need to make the connections myself.
The only problem I have is that I'm not sure which terminal is live and which is neutral. I don't see any signs indicating which is which. So does it matter?
You should be able to determine which terminals are neutral (or rather common between input and output) by measuring resistance between each of the 220V terminals and each of the 110V terminals. All resistances will probably be very low, but the lowest resistance combination should be the common terminals,and you would use those as Neutral.
You would need to check the resistance between the terminals on the 220 V terminal block and the 110 V one.
The terminals between which the resistance is the lowest would be the neutral terminals.
If it's a 220 volt in and 110 volt out auto transformer then there are only 3 effective connections and there should be symmetry like this: -
simulate this circuit – Schematic created using CircuitLab
So, all you have to do is find the middle centre-tap connection. You can do this by applying a 50/60 Hz AC voltage to the 220 volt side (up to 220 volts) and looking for half that applied voltage on the 110 volt winding using a voltmeter.
I use a no contact ac voltage tester. The tester flashes and beeps only when the tip is close to the hot lead. This is true on both the 220 and 120 connections. This is also the same, with the more common isolated primary and secondary transformer.
