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- Single Phase Motors
Rotor
• Similar to a 3 phase
induction motor with
squirrel cage rotor and
main stator windgs. Laminated stator slots
Wndgs
Centrifugal switch
Main wndgs
Start wndgs
- 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.
- Φm
Starting Torque in Single phase motor
Split Phase Principle
• 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 Φ m while
the Aux wndg produces a flux Φa
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.
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