armature reaction of an alternator influences
(A) windage losses
(C) generated voltage per phase
of voltage generated.
the same power rating, a lower voltage alternator will be
(B) larger in size
(C) operating at high rpm
alternator is supplying 10A to an inductive load at 220 V, while running at
1000 rpm. Now if the speed of the alternator is reduced to 750 rpm but the
field current remains unchanged, the load current will become
(B) 13.3 A
(D) 7.5 A.
in a large generator
alternator is rated for 75 kW at 0.8 power factor. It means that
has 4 poles
can supply 75 kW at 0.8 power factor
can supply power only to loads having power factor 0.8 only
peak efficiency of alternator occurs only at 75 kW load having 0.8 lagging
regulation of an alternator is
reduction in terminal voltage when alternator is loaded
variation of terminal voltage under the conditions of maximum and minimum
increase in terminal voltage when load is thrown off
change in terminal voltage from lagging power factor to leading power factor.
magnetisation curve represents the relationship between
(A) reactive and non-reactive components of
(B) exciting currents and terminal voltage
(C) power factor and terminal voltage
(D) magnetic flux and armature current.
an alternator if the armature reaction produces magnetisation of the main field
the power factor should be
(A) Zero, leading load
(B) Zero, lagging load
an alternator is supplying unity power factor load, the armature reaction will
(A) magnetisation of the main field
(B) demagnetisation of the main field
(C) distortion of the main field.
alternator has full load regulation of 4% when the power factor of the load is
0.8 lagging while alternator runs at 1500 rpm. The full load regulation of 1400
rpm for 0.8 pf lagging load will be
15/14 x 4
14/15 x 4 percent
on other factors also.
Potier’s triangle separates the
(A) iron losses and copper losses
(B) field mmf and armature mmf
(C) stator voltage and rotor voltage
(D) armature leakage reactance and armature
the Potier’s triangle, the Potier reactance drop per phase is 22 volts per
phase at 88
per phase. The Potier’s reactance per phase is
alternators are running in parallel. The excitation of one of the alternator
is increased. The result will be
(A) machine with excess excitation will burn
(B) both machines will start vibrating
(C) power output will decrease
(D) wattless component will change.
power output of an alternators is 100 kW. In order that the tangent of pf angle
may be 0.8 lagging, the KVAR rating must be
(A) 80 cosφ KVAR
(B) 80 sin φ KVAR
(C) 80 KVAR
(D) -80 KVAR.