Interested to Buy Any Domain ? << Click Here >> for more details...
Synchrounous motor is three phase motor,but its not self
starting .why?
- 23 Answers
- 57720 Views
- Delta Beverages, KI, L&T, NTC, TVS, Wipro, I also Faced
- E-Mail Answers
Answer Posted / abhishek kumar
In order to understand the principle of operation of a
synchronous motor, let us examine
what happens if we connect the armature winding (laid out in
the stator) of a 3-phase
synchronous machine to a suitable balanced 3-phase source
and the field winding to a D.C
source of appropriate voltage. The current flowing through
the field coils will set up sta-
tionary magnetic poles of alternate North and South.On the
other hand, the 3-phase currents flowing in
the armature winding produce a rotating magnetic field
rotating at synchronous speed. In
other words there will be moving North and South poles
established in the stator due to the
3-phase currents i.e at any location in the stator there
will be a North pole at some instant of
time and it will become a South pole after a time period
corresponding to half a cycle. (after
a time = 1/2f
where f = frequency of the supply). Let us assume that the
stationary South
pole in the rotor is aligned with the North pole in the
stator moving in clockwise direction
at a particular instant of time.These two poles get
attracted and try to maintain this alignment ( as per lenz’s
law) and hence the rotor pole tries to follow
the stator pole as the conditions are suitable for the
production of torque in the clockwise
direction. However the rotor cannot move instantaneously due
to its mechanical inertia, and
so it needs sometime to move. In the mean time, the stator
pole would quickly (a time
duration corresponding to half a cycle) change its polarity
and becomes a South pole. So
the force of attraction will no longer be present and
instead the like poles experience a force of repulsion.In
other words, the conditions are now suitable for the
production of torque in the anticlockwise direction. Even
this condition will not last longer
as the stator pole would again change to North pole after a
time of 1/2f. Thus the rotor will
experience an alternating force which tries to move it
clockwise and anticlockwise at twice
the frequency of the supply, i.e. at intervals corresponding
to 1/2f seconds. As this duration is
quite small compared to the mechanical time constant of the
rotor, the rotor cannot respond
and move in any direction. The rotor continues to be
stationary only. so need some prime mover
| Is This Answer Correct ? | 9 Yes | 2 No |
Post New Answer View All Answers
700KW 6.6KV slip ring induction motor to use VFD to control the speed
How can i calculate the Breaking capacity of molded case circuit breaker, is the breaking capacity of CB for Diesel generator shall be less than grid supply's breaker ?
What is the abbreviation of NGT panel
i have gear oil pump with single phase motor.some time its motor starts running in reverse direction rather than forward direction...whats the reason behind this issue. 1- either capacitor is week? 2- or winding is week?
what are the difference between PLC and embedded
we are having 15kw and 3kw motor both can run in same time , instead of using copper we are using ug aluminium cable , 35 sq.mm is suitable for its current carrying capacity..?
What will be the diameter of pipe between conservation tank and transformer
whats the differece between Exd and Exe
can we use engine degreaser for electrical motors?
Working of microwave oven?
Why in 6 KV XLPE cable termination kit used and why not in 380 V xlpe cable same is not used
Main advantage of auto transformer over two windings transformer is that A it needs no cooling B it uses only one winding C core losses are reduced D it has simple construction
what is the function of choke in the flourcent tube lights and why the colour is in white mostly in flourcent tube lights
What are unstable systems?
After synchronization with grid what is the demand value QKVAR and how we will maintain that?
