Yes, Transformers which operate on 110 - 120 Volts exist. This question is probably incomplete as it only mentions one voltage: it could be for the primary or the secondary or for a single-winding auto-transformer. The missing information cannot be guessed...
By using a step down transformer.
to derive 120 volts from 480 volts you have to use a transformer, based on your needs. If you needed 100 amps at 120 volt single phase you would need a 12kva transformer. This is just an example.
Get yourself a 1:4 step up transformer.
A transformer is needed to convert 110 v to 220 v or vice versa. This type of transformer is commonly used in Europe for power tools in the building trade which run from a portable 110 v transformer with a centre-tapped earth for safety so that each side is only 55 v to earth. A 3 kVA transformer for this purpose costs about £80.
The formula you are looking for is I = W (VA)/E. Amps = Watts/ Volts.
Volts cannot be converted to amps. If you mean convert 220v to 12 volts output, then you need a 220v to 12 v step down transformer with the VA or watt rating you require.
By using a step down transformer.
If you get 220 volts instead of 208 volts it means that the transformer supplying the circuit is wired in Delta with one of the legs center-tapped to ground.
I guess you have a chiller unit suitable for 380Volts and you have a source voltage of 220V. You can step up 220Volts to 380 volts with a suitable rated step up transformer.
If it is AC voltages you need to convert, you need to find a transformer to do this job. Without knowing the application it is hard to guess what you are trying to do.
to derive 120 volts from 480 volts you have to use a transformer, based on your needs. If you needed 100 amps at 120 volt single phase you would need a 12kva transformer. This is just an example.
The only way to do that is with a transformer. They make inline transformers that convert 230 to 115 and they simply plug in inline.
Get yourself a 1:4 step up transformer.
A transformer is needed to convert 110 v to 220 v or vice versa. This type of transformer is commonly used in Europe for power tools in the building trade which run from a portable 110 v transformer with a centre-tapped earth for safety so that each side is only 55 v to earth. A 3 kVA transformer for this purpose costs about £80.
If it is AC then you don't need a formula, you just need a transformer.
A transformer that reduces voltage is classed as a step down transformer.
If you want to convert 24v AC into 12v Ac, it's simple. Just get a transformer to convert 24 volts into 12 volts. This is called a stepdown transformer. If you want to convert 24v DC into 12v DC, it's more complicated. First you have to change the 24v DC into 24v AC by a switching converter that changes DC into AC. Then you would use a stepdown transformer as in the former example. Once the 24v AC is converted to 12v AC, then you use a rectifier bridge to change the 12v AC into 12v DC.