In a synchronous motor armature current flows due to
revolving flux which in turn rotates the load,but in no
load condition armature current is zero hence thr is no
revolving flux then how motor rotates?
Answers were Sorted based on User's Feedback
Answer / md fakruddin
syn.motor isnot self starting.so we have start with some
other arrangements .one of the best ones is by damper
winding .damper winding is shorted on both side of rotor,as
by induction motor princepal motor rotate itself ,and
magnetic locking between rotor poles and stator occures and
motor runs.at no load armature current is not zero as there
are losses .and there is no relation between armature
current and load because motor hs started already .
Is This Answer Correct ? | 5 Yes | 0 No |
Answer / amrita
When syn motrr is at no load, armature draws current
required for magnetisation.
As supply having some freq. so field flux continues 2
rotate at syn speed.
In syn motor speeed is constant from noload 2 full load.
Is This Answer Correct ? | 4 Yes | 1 No |
Answer / phani
Due to residual magnetism some flux will be developed.
Is This Answer Correct ? | 3 Yes | 1 No |
Answer / joy
Even on no load condition, the stator is connected
to 3ph ac supply. This 3ph ac supply produces a
rotating magnetic field, which links with the
rotor. Since the rotor was in a rotating condition
it continues to rotate as long as there is presence
of rotating stator flux. The rotor and stator flux
are synchronously locked with each other even on no
load condition.
Is This Answer Correct ? | 3 Yes | 1 No |
Answer / kumar gaurav
IN FACT ARMTURE CURRENT FLOWS ALL THE TIME TO SET UP THE
AIR GAP FLUX "AS LEAKAGE AND MUTUAL FLUXES" WHICH ROTATES
AT SYNC. SPEED, BUT IN CASE OF LOAD REQD. MUTUAL FLUX
INCREASES AND HENCE THE CURRENT INCREASES WHILE IN CASE OF
NO LOAD 30%OF RATED CURRENT REQD. TO SET UP THE AIR GAP
FLUX.
Is This Answer Correct ? | 1 Yes | 0 No |
Answer / utsav datta
After starting of the synchronous machine,armature current
is always present to set an air gap flux rotaing at
synchrous speed.
Is This Answer Correct ? | 2 Yes | 1 No |
Answer / amita sharma
DUE TO RESIDUAL MAGNETISM THERE IS SOME FLUX WHICH INDUCES
EMF IN THE ROTOR AND THERE FORE THE MOTOR ROTATES.
Is This Answer Correct ? | 2 Yes | 2 No |
This is funny , how on earth could u assume that the no
load condition of a motor means open circuit condition ,
now listen the 3 phase supply given to stator produces a
rotating magnetic flux which reacts wit the initially at
rest field conductors to set up an induced emf lagging the
flux by 90* , but the field mmf set up leads the stator mmf
and rotates in the same direction as the rotating field (
note that i m already considering that the motor has
starting mechanism i.e. damper winding and later on dc
excitation ) thus the two rotating mmfs are stationary wrt
to each other but rotating at synchronous speed wrt
stator , since the rotor mmf i.e field mmf has the tendency
to follow the resultant air gap mmf so electromagnetic
torque acts that sets the rotor rotating . it must be noted
that the field mmf is proportional to field current while
the armature mmf is prprtnl to armtr crrnt , hence at no
load the armature mmf is maxm, because the arm current is
maxm, while with increase in load the current decreases and
hence the arm mmf , however the reasultant air gap mmf
always remain constant till voltage supply and the
frequemncy are maintained constant, it is only that the
field mmfs and the armature mmfs change in orientation and
magnitude.
Is This Answer Correct ? | 0 Yes | 1 No |
Answer / sprabhu
Even No Load is connected the induced emf drives the
armature current as the coils are short circuited at the
ends, which makes the machine to rotate
Is This Answer Correct ? | 0 Yes | 2 No |
What is the difference between SSR drive& AC drive?
can anybody send the rrb chennai &rrb bopal question papers of 2006&2007.My exam is on 12 oct 2008.Its urgent
how to calculate the earthing conductor & no. of earth pits required
What are the types of instrument transformer?
Why does the adjacent zone of protection overlap?
Explen all type electrical protection ? like O/C,E/F,NPS,VOLTAGE UN BLANCE,CURRENT UN BALANCE,NAGETIVE PHASE SEQ,AND ETC...............electrical Protection
On wat basis TSM & PSM are set? Example.TSM=30% n PSM=2.5A....Hw they are set and how we come to know that the particular relay should be set to this value only?
What will happen to the speed of synchronous machine subjected beyond the pull out torque? Are the behavior shown by rotor remains same for both the alternator and motor?
how to carry out Magnetizing Current Test on Distribution transformer and what purpose we are doing this test.
Why we make earth connection with Transformer Body and What will be the minimum size of copper wire as per code with respect to KVA rating of Transformer?
avr is an automayic voltage regulator ... it regulates voltage before it synchronise with grid after synchronisation it regulates power factor why....
Why the motor take high starting current for long time(10- 15 sec) which is connected to Blower as compaire with a motor which is connected with pump with same rating?