A Best Way To Crack Gorenment Job Exams

Electrical Engineering Objective Questions { DC Motors }

155. In a dc generator operating on load with its brushes on the geometrical neutral axis (GNA), the magnetic neutral axis (MNA) is shifted in the direction of rotation Now, if the brushes are given a lead of 90? (electrical), then the MNA will
A. shift forward by 90?
B. shift forward by more than 90?
C. shift forward by less than 90
D. coincide with the GNA
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156. A bipolar de machine with interpoles has a mainpole flux of 4) per pole and an inter-pole flux of 4); per pole. The yoke of the machine is divided into four quadrants by the main-pole axis and the commutation axis.The flux-distribution in the quadrants will be
A. ?2 (6 + 6,) in all the four quadrants
B. ?2 (6 -- 4),) in all the four quadrants
C. ?2(6 + 4),) in two diametrically opposite quadrants and ?2 (4) ? 61) in the remaining two quadrants
D. ?2 (6 + 6,) in two adjacent quadrants,and ?2(4) ? 4),) in the remaining two quadrants
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157.  A cumulatively compounded dc motor runs at 1000 rpm at no-load. On full load, the flux increases by 10%, whereas the full load drop in the combined resistance of the armature and series field is 5%. Neglecting magnetic saturation, the full load speed will be nearly
A. 863 rpm
B. 909 rpm
C. 1000 rpm
D. 1050 rpm
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158.  A 6-pole lap-connected de generator with 480 conductors has an armature resistance of 0.06 ohm. lithe conductors are reconnected to form a wave winding, other things remaining unchanged, the value of the armature resistance will be
A. 0.01 ohm
B. 0.06 ohm
C. 0.36 ohm
D. 0.54 ohm
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159. A 2-pole series motor with its two field coils connected in series runs at a speed of 500 rpm. If the field coils ar reconnected in parallel and assuming that the torque is constant and the magnetic circuit is unsaturated, the new speed will be
A. 250 rpm
B.500 rpm
C. 500 Nri rpm
D. 1000 rpm
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160. On direct on line (DOL) starting, dc motor is found to rotate in the direction opposite to that for which it was designed. The motor is a
A. series motor
B. shunt motor
C. cumulatively compounded motor
D. differential compounded motor
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161. In a dc machine, the armature mmf is
A. rectangular and directed along the interpolar axis
B. triangular and directed along the inter-polar axis
C. traingular and directed along the brush axis
D. rectangular and directed along the brush axis
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