Manali: Himachal Pardesh

• Enclosure

• Stator

Stator (Windings)

• “Stationary” part of the motor sometimes referred to as “the

windings”.

• Slotted cores made of thin sections of soft iron are wound

with insulated copper wire to form one or more pairs of

magnetic poles.

• Rotor

Rotor

• “Rotating” part of the

motor.

• Magnetic field from

the stator induces an

opposing magnetic

field onto the rotor

causing the rotor to

“push” away from the

stator field.

Wound Rotor Motors

• Older motor designed to operate at “variable speed”

• Advantages

– Speed Control, High Starting Torque, Low Starting Current

• Disadvantages

– Expensive, High Maintenance, Low Efficiency

• Bearings

• Conduit Box

• Eye Bolt

Watt’s Law

• Input Power

• Single Phase

– Watts = Volts X Amps X p.f.

• Three Phase

– Watts = Avg Volts X Avg Amps X p.f. X 1.74

Example

• Is a 1 Hp 1-phase motor driving a fan overloaded?

– Voltage = 123 volts

– Current = 9 amps

– p.f. = 78%

• Watts = Volts X Amps X p.f.

Watts = 123 volts X 9 amps X 0.78 = 863.5 Watts

864 Watts / 746 Watts/Hp = 1.16 Hp

• Is the motor overloaded?