3-phase Motors - 1
Rotating Magnetic Field
3-phase Supply
(3 voltages, 120o apart)
3-phase Motor Stator
(3 Windings, 120o apart)Phase A (Red)
Phase B (Black)Phase C (Blue)
Arrows show Magnetic Fluxwhen phase voltage is POSITIVE
A B C
3-phase Motor Stator
(3 Windings, 120o apart)
Each step is shownhere at 0.5 seconds(6 seconds per cycle)
Green dotted lines show resulting magnet flux
Green arrow shows flux direction
Three-phase sequence produces resulting ROTATINGMAGNETICFLUX
3-phase Motor Stator
(3 Windings, 120o apart)
Each step is shownhere at 0.2 seconds(2.4 seconds per cycle)
3-phase Motor Stator
(3 Windings, 120o apart)
Each step is shownhere at 0.1 seconds(1.2 seconds per cycle)
3-phase Motor Stator
(3 Windings, 120o apart)
This shows continuous1 second per cycle
3-phase Motor Stator
(3 Windings, 120o apart)
The STATOR core is a stack of thin silicon steel LAMINATIONS
3-phase Motor Stator
(3 Windings, 120o apart)
Windings are coils placed in SLOTS around the STATOR
The coils are connected in groups for each of the THREE PHASES
Speed – Frequency - Poles
The SPEED of the rotating magnetic fieldis determined by:
Supply FREQUENCY in Hertz (Hz)
Number of magnetic POLESproduced by the stator windings
Speed – Frequency - PolesThe SPEED of the rotating magnetic field is determined by:
120Synch
fN
P
SynchronousSpeed (rpm)
Frequency(Hz)
Number of Polesper phase
x2 Poles to PAIRSx60 rps to rpm
Production of Torque
Production of Torque
Note that the ROTOR LAGS behind the rotating magnetic field
(Watch the pink dot)