Home / Comparisons / Difference between Single Phase and Three Phase Induction Motor 

Difference between Single Phase and Three Phase Induction Motor 

The main difference between single phase induction motor and three phase induction motor is that single phase motors are NOT self-starting so they require some starting mechanism while three-phase motors are self-starting. Furthermore, single phase motor requires ONLY single phase supply so they produce an alternating magnetic field whereas three phase motor requires three phase supply so they produce rotating magnetic field.

Single phase IM is mainly utilized in household applications like in fans, refrigerator, grinder, and Air Conditioner. Three phase IM is primarily used in various industries, factories such as paper mills and for traction purposes.

The differences between single phase and three phase induction motor are explained on the basis of very important practical factors such as power source, starting mechanism, starting torque, cost, operational reliability, power factor, size, maintenance, structure, and uses.The following table presents the key differences between single-phase induction motor and three phase induction motor.

Difference between Single Phase and Three Phase Induction Motor 

Characteristics Single Phase induction MotorThree Phase Induction Motor
Power SourceSingle Phase (1-phase) OnlyGenerally requires more than a single phase power source (like 3-phase supply).
Starting MechanismThey are NOT self-starting.They are self-starting.
Efficiency Low as only one winding has to carry all the currentHigh because three winding are available to carry the current
TypesShaded pole
Split Phase
Capacitor Start Inductor Run
Capacitor Start Capacitor Run
Squirrel cage type
Slip ring type or wound induction motor
CostCheaperQuite Expensive
Slip (s)There are two slips:
Forward slip (s)
Backward slip (2-s)
It has only forward slip
Size (for same power rating)Larger in sizeSmaller in size
Power FactorLowHigh
Repair & MaintenanceEasier to repairDifficult to repair and maintain
StructureSimple and easy to manufactureMore complicated to construct because of extra components involvement
Starting TorqueLowHigh
Operational Reliability More ReliableLess Reliable
Motor RotationThere is no mechanism to change the rotation.Can be changed easily by changing the phase sequence in stator.
UsesFrequently used for lighter loads. such as:
Vacuum cleaner fans
Centrifugal pump
Washing machine
Extensively employed in industrial and commercial drives since they are more rugged and economical in terms of operational efficiency.

About Ahmad Faizan

Mr. Ahmed Faizan Sheikh, M.Sc. (USA), Research Fellow (USA), a member of IEEE & CIGRE, is a Fulbright Alumnus and earned his Master’s Degree in Electrical and Power Engineering from Kansas State University, USA.

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