Single Phase Motors
•Similar to a 3 phase
induction motor with
squirrel cage rotor and
main stator windgs.
Main wndgs
Start wndgs
Laminated stator slots
Rotor
Wndgs
Centrifugal switch
Run (main) and Start (Aux) Windings
•The stator has two sets of
windgs, Run (which is of
thicker size to reduce I²R
losses) and Start of thinner
size is placed 90˚ apart.
•Run has relative Large
number of turns.
•Aux has relative Small
number of turns.
Starting Torque in Single phase motor
•To produce a starting torque a
rotating magnetic field must be
produced.
•This is done by including the Aux
winding.
•When an AC source is applied the
main windg produce a flux while
the Aux wndg produces a flux
Since the angles are out of phase a
resultant rotating field is created
•A centrifugal switch disconnects the
Aux. wndg from the supply after it
has run up to 75% of full speed.
m
Φ
m
Φ
aΦ
Split Phase Principle