1. What is Single Phase?
Single phase is commonly used for homes and small electrical loads.
- Voltage: about 230 V AC in India
- Wires: Phase (L) + Neutral (N) + Earth (E)
- Frequency: 50 Hz
- Common uses: lights, fans, TV, refrigerator, small pumps, household sockets
- Typical supply: 230 V between Phase and Neutral
Example:
Phase → Switch → Load → Neutral
2. What is Three Phase?
Three phase is mainly used for larger loads and machines.
- Voltage: about 400–415 V between two phases
- Wires: R, Y, B phases + Neutral (if required) + Earth
- Frequency: 50 Hz
- Common uses: motors, pumps, compressors, industrial machines, large buildings
- Phase-to-neutral voltage: about 230 V
- Phase-to-phase voltage: about 400–415 V
3. Main Difference
| Point | Single Phase | Three Phase |
|---|---|---|
| Number of phases | 1 | 3 |
| Phase names | L | R, Y, B |
| Phase-Neutral | ~230 V | ~230 V |
| Phase-Phase | — | ~400–415 V |
| Main use | Homes | Industry/large loads |
| Motor operation | Smaller motors | Efficient for larger motors |
| Wires | L + N + E | R + Y + B + N + E |
4. Important Electrical Terms
- Voltage (V): Electrical pressure
- Current (A): Flow of electric charge
- Resistance (Ω): Opposition to current
- Power (W): Rate of electrical energy use
- Energy (kWh): Electricity consumed
- Frequency (Hz): Number of AC cycles per second
- Phase: Live conductor carrying AC supply
- Neutral: Return/reference conductor
- Earth: Safety path for fault current
5. Basic Formulas
Single Phase:
Power = Voltage × Current × Power Factor
Three Phase:
Power = √3 × Voltage × Current × Power Factor
For electrical work, always isolate the supply and verify it is dead before touching conductors.
