VISITORS: 9

A three-phase EMF of an alternator is generated when three identical stator windings are placed 120° electrical apart and a rotating magnetic field induces sinusoidal EMFs in them. The three generated phase EMFs have the same frequency and magnitude but are displaced from each other by 120° electrical. They can be represented as $E_A=E_m\sin\omega t$ , $E_B=E_m\sin(\omega t-120^\circ)$ , and $E_C=E_m\sin(\omega t-240^\circ)$ . These three EMFs form a balanced three-phase supply and can be connected in star (Y) or delta (Δ) configuration for transmission and distribution of electrical power.

Three-Phase EMF Alternator Simulation

Three-Phase EMF of an Alternator

Interactive demonstration of three sinusoidal EMFs displaced by 120° electrical

Simulation Controls

Frequency: 50 Hz

Phase Voltage: 230 V

Rotor Speed: 1500 RPM

Connection

Animation

Reset

1. Rotating Magnetic Field and Three Stator Windings

Rotor angle: 0°

PHASE A
Position: 0°
EA = 0 V

PHASE B
Position: 120°
EB = -199 V

PHASE C
Position: 240°
EC = +199 V

2. Three-Phase EMF Waveforms

Three-phase EMF equations:

EA = Em sin(ωt)
EB = Em sin(ωt − 120°)
EC = Em sin(ωt − 240°)

Angular frequency: ω = 2πf

3. Three-Phase Connection

Star Connection (Y)

In a star connection, one end of each phase winding is connected to a common neutral point.

For a balanced system:

VL = √3 × Vph

The three phase voltages are separated by 120°.

Delta Connection (Δ)

In a delta connection, the three phase windings are connected end-to-end to form a closed loop.

For a balanced system:

VL = Vph

The three phase EMFs still maintain their 120° phase relationship.