Old transformer input output
Since this transformer is from a UPS it will be used as both a step-down transformer for charging the battery, and a step-up transformer to generate 230Vac from the battery voltage. Because of this it is wrong to refer to the windings as primary and secondary, it is probably better to refer to them as high and low voltage windings.

Most small UPS transformers have 3 windings:


High voltage winding.
Low voltage winding. Typically around 12Vac
A sense winding. Typically around 3Vac but with little power available.


The 2 separate wires probably connect to the low voltage winding since they have high current ring crimp terminals on them. 2 of the wires in the connector will be the 230Vac winding, and the other 2 wires will be the "sense" winding so the UPS can sense the voltage it is generating. It's not possible to guess which is which.

Since the transformer is made by Intex it probably comes from an Intex UPS. You may be able to work out which wires are mains and which are sense wires by getting a circuit diagram of the UPS.