Saturday, 18 January 2020

What is AC Servomotor? and What is Universal Motor or AC series motor?

AC Servomotor:-                                                                                                                     

AC Servomotor
AC Servomotor


The main parts in construction of AC Servomotor are stator and rotor.

  • The a.c servo motor is basically consists of stator and rotor. The stator carries two winding.   
  • One winding is called as main winding or reference winding is excited by constant voltage source.
  • And other winding is called as control winding is excited by variable control voltage. 
  • The winding are 90 away from each other and control voltage is 90 out of phase with respect to the voltage applied to main winding.
  • This necessary to obtain rotating magnetic field.

  •  Rotor is generally two types 

  1. Squirrel cage rotor 
  2. Drag cup type rotor.

Operating principle:-

1. The operating principle of AC servo motor is same as that of normal three phase induction motor.
2. The control voltage is applied to control winding and the voltage applied to the main winding are 90 out of phase.
3. Hence flux produced by current through the control winding is also out of phase with respect to flux produced by the main winding.
4. The resultant flux in the air gap is hence rotating nature is called as rotating magnetic field.
5. The rotor is stationary at start. But rotating magnetic field rotate over surface of the rotor, and EMF get induced in rotor.
6. This  EMF circulate the current through the rotor.
7. The rotor current produced its own flux called as rotor flux.
8. This flux inter acts with the rotating magnetic field, produced a torque on rotor and rotor start rotating.

Application of Ac Servo Motor:-

  • Machine tool.
  • Robotics.
  • Process controller.
  • Self-balancing recorder.

Universal motor or A.C. series motor:-

Universal Motor
Universal Motor

There is small capacity series motor which can be operated on D.C supply or single phase A.C supply  of same voltage with similar characteristics, called as “ universal motor “

The general construction of such motor is similar to that of A.C  series motor.
It is manufactured in two types:-
i.                    Non- compensated (Low H.P).
ii.                  Compensated type (High H.P).

Non- compensated type universal motor has 2 poles having entire magnetic path as laminated.

 Reversal of rotation of universal motor is obtained by changing connection of armature winding. 
As well as speed reversal is obtained by changing connection of field winding.


Universal motor work’s on principle of “when a current carrying conductor is placed in a magnetic field, the conductor experience a mechanical force” the direction of this force is given by Fleming’s left hand rule.
1. When motor is connected to an A.C. supply, the same alternating current which flows through armature and field winding.

2. The field winding produced alternating flux (ϕ) that reacts with current flowing through in armature which produced a torque.

3. Since both armature and flux reverse simultaneously, the torque always same direction.

4. It may note that no rotating magnetic field produced in this types of motor.

  • High speed vacuum cleaner.
  • Sewing machine.
  • Food processors.
  • Mixer and grinder.
  • Drilling machine.

Reversal of rotation:
  • The reversal of rotation of universal motor is carried out by changing one of winding (armature or field winding) connection.
  •  Reversal of rotation of universal motor is obtained by changing connection of armature winding as well as speed revers al is obtained by changing connection of field winding.



Nellie Morrison said...

Your articles are very well written and unique.
isolation transformer

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