DC Generators

Severe sparking Rough commutator surface Imperfect contact Any of the above Graphite Paper Mica Insulating varnish Oscillating magnetic field Pulsating magnetic flux Relative rotation between field and armature All above Compensating winding in a D.C. machine helps in commutation In a D. C. generator interpoles winding is connected in series with the armature winding Back pitch and front pitch are both odd and approximately equal to the pole pitch Equalizing bus bars are used with parallel running of D.C. shunt generators Using conductor of annealed copper Using commutator with large number of segments Using carbon brushes of superior quality Using equaliser ring There is no load on the generator The generator runs on full load The generator runs on overload The generator runs on designed speed Neutralise the commutating self induced e.m.f. Neutralise the armature reaction flux Neutralise both the armature reaction flux as well as commutating e.m.f. induced in the coil Perform none of the above functions Identified by the scarring of the commutator segment to which open circuited coil is connected Indicated by a spark completely around the commutator Both (A) and(B) None of the above External resistance = internal characteristic armature reaction Internal characteristic = magnetisation characteristic ohmic drop External characteristic = magnetisation characteristic ohmic drop armature reaction Magnetisation characteristic = external characteristic Shunt generators Series generators Compound generators None of the above 2 : 3 3 : 1 3 : 2 1 : 3 Interpoles Dummy coils Compensating winding Shifting of axis of brushes Abrasion from dust Excessive spring pressure Rough commutator bars All of the above factors Zero About 2 V About 50 V 220 V 150 V Less than 150 V Greater than 150 V None of the above Blv Blv2 Bl2v Bl2v2 Self-excited generator Separately excited generator Level compounded generator All of the above Armature reaction Armature resistance drop Field weakening due to armature reaction and armature Commutation Rectifier Prime mover Rotating amplifier Power pump 150 V 175 V 240 V 290 V