Questions and answers on single-phase motors.
How would you reverse the direction of rotation of a capacitor start-induction-run motor?
By reversing either the running or starting-winding leads where they are connected to the lines. Both must not be reversed.
In which direction does a shaded-pole motor turn?
It runs from the unshaded to the shaded pole.
Can such a motor be reversed?
Normally, such motors are not reversible because that would involve mechanical dismantling and re-assembly. However, special motors are made having two rotors on a common shaft, each having one stator assembly for rotation in opposite direction.
What is universal motor?
It is built like a series d.c. motor with the difference that both its stator and armature are laminated. They can be used either on d.c. or a.c. supply although the speed and power are greater on direct current. They cannot be satisfactorily made to run at less than about 2000 r.p.m.
How can a universal motor be reversed?
By reversing either the field leads or armature leads but not both.
How can we reverse the direction of rotation of repulsion, repulsion-induction and repulsion-start-induction-run motor?
By shifting the brush positions by about 15 electrical.
How can we reverse the rotation of a 1-phase, split-phase motor?
By reversing the leads to either the running or starter winding but not both.
What could be the reasons if a repulsion induction motor fails to start?
Any one of the following
No supply voltage
Low voltage
Excessive overload
The bearing lining may be stuck or “frozen” to the shaft
Armature may be rubbing
Brush yoke may be incorrectly located
Brush spacing may be wrong
What could by the reasons if a spiit-phase motor fails to startand lnuas laudly
It could be due to the starting winding being open or grounded or burut out.
What could be the reasons if a spht phase motor runs too slaw?
Any one of the following factors could be responsible
Wrong supply voltage and frequency
Overload
Grounded starting and running windings
Short-circuited or open winding in field circuit