Single Phase Motor: Questions Answered

  • Thread starter Thread starter NT DANG KHOA
  • Start date Start date
  • Tags Tags
    Motor Phase
Click For Summary
SUMMARY

The discussion centers on the operation of single-phase induction motors, specifically addressing their non-self-starting nature and the role of start windings and capacitors. It is established that a single-phase motor requires an external force to initiate rotation due to opposing magnetic fields generated by the main winding. The start winding, positioned at a 90° phase angle to the main winding, along with a start capacitor, creates a rotating magnetic field that allows the motor to reach its rated speed. Once operational, the induced current in the armature maintains rotation despite the presence of opposing forces.

PREREQUISITES
  • Understanding of single-phase induction motor design
  • Knowledge of AC motor principles
  • Familiarity with phase shifting in electrical circuits
  • Basic concepts of magnetic fields and torque generation
NEXT STEPS
  • Research the operation of single-phase induction motors with starting capacitors
  • Learn about the role of slip in AC motors and its effect on torque
  • Explore the design and function of start windings in single-phase motors
  • Investigate the impact of phase difference on motor performance and efficiency
USEFUL FOR

Electrical engineers, motor design specialists, and students studying motor control and electrical machinery will benefit from this discussion.

NT DANG KHOA
Messages
2
Reaction score
0
Dear expert, dear all.
As my knowledge, the single phase motor is not a seft-starting motor. i suppose that there is only main winding in single phase motor.
as you know, the rotor can not start because of the 2 opposites force cause by 2 oppositely rotating magnetic fields.
the question is that :
1. Why we give the 1 phase motor an external force in either direction , the motor will start to run ? ( i think the motor only run for short time until this force run out , because it always exist 2 opposites force when the main winding of stator have power supply. like we turn the wheel by hand )
2. with a normal single phase motor ( starting winding with a capacitor and main winding ) what is the cause can make the speed of the motor increase because the capacitor and the starting winding only give it the constant force in the starting period, and why we cut out the starting winding , the motor continue increase speed to the rated speed while there is only 1 main winding which have cause the 2 same opposites force ?
Forgive me if my eng is not good and it is a stupid question,
thank in advance.
 
Engineering news on Phys.org
Welcome to PF.

A single phase induction motor has a start winding that is wound at 90° phase to main winding.
The start capacitor provides a phase shifted current that excites the start winding.
The sum of the magnetic field from main and start winding is a true rotating vector field.

Once the motor is running the current induced in the armature is sufficient to maintain rotation.
 
Baluncore said:
Welcome to PF.

A single phase induction motor has a start winding that is wound at 90° phase to main winding.
The start capacitor provides a phase shifted current that excites the start winding.
The sum of the magnetic field from main and start winding is a true rotating vector field.

Once the motor is running the current induced in the armature is sufficient to maintain rotation.
SORRY BUT COULD YOU EXPLAIN MORE DETAIL ABOUT THIS SENTENCE "Once the motor is running the current induced in the armature is sufficient to maintain rotation"
 
The current induced in the rotating armature has a phase delay that makes it not parallel with the field windings.
Because there is a phase difference between armature and main winding there is a directional torque.
http://en.wikipedia.org/wiki/AC_motor#Slip
 

Similar threads

How does a Permanent capacitor motor actually work?
  • · Replies 7 ·
Replies
7
Views
2K
Self excited induction generators and grid connected solar inverters?
  • · Replies 9 ·
Replies
9
Views
2K
Induction motor windings, number of turns per phase and per pole
  • · Replies 2 ·
Replies
2
Views
4K
Induction motor rotor design features
  • · Replies 4 ·
Replies
4
Views
3K
Asymmetrical grounding of a 3 phase motor being run on a 1 phase supply
  • · Replies 7 ·
Replies
7
Views
3K
Series motors, switched to parallel
  • · Replies 11 ·
Replies
11
Views
567
Increasing induction motor frequency
  • · Replies 9 ·
Replies
9
Views
3K
Capacitors on motors: why big C for starting, small for running?
  • · Replies 4 ·
Replies
4
Views
2K
What is the minimum number of poles in single phase motor
  • · Replies 1 ·
Replies
1
Views
14K
Fan motor stalling on running winding
  • · Replies 7 ·
Replies
7
Views
3K