The difference in one paragraph
A single-phase supply delivers power on one live conductor and a neutral. A three-phase supply delivers it on three live conductors whose voltages peak one after another, a third of a cycle apart. That staggering means the power never drops to zero, which is why three-phase is smoother for motors and can carry more load on thinner cable.
In India a single-phase supply is nominally 230 V between live and neutral. A three-phase supply is nominally 415 V between any two lives, and 230 V between any one live and neutral.
How to tell which supply you have
You rarely need an electrician just to find out. Any one of these usually settles it:
- The service cable: one live and a neutral is single-phase; three lives (often red, yellow and blue) and a neutral is three-phase.
- The meter: a three-phase meter is larger and shows readings for three phases.
- The electricity bill: the connection type and sanctioned load are printed on it.
- The distribution board: three-phase boards carry a four-pole main switch or three single-pole breakers ganged together.
Which one suits which job
Single-phase transformers suit homes, offices, clinics and shops, where the load is lighting, fans, computers and the odd pump. Three-phase transformers suit anything that runs three-phase motors: flour and rice mills, saw mills, workshops with lathes and compressors, cold stores, hotels with large kitchens and lifts.
If you have a three-phase supply but only single-phase equipment, a single-phase unit on one phase can work — but a large single-phase load on one phase unbalances the supply. Spreading loads across all three phases is usually the better plan.
Before you ask for a quote
Know your supply type, the voltage you want out, and the total load you intend to run. With those three facts a supplier can narrow the choice to one or two ratings straight away.
General guidance only — every installation is different. For work on live equipment, use a licensed electrician. Last reviewed 28 September 2026.