Description : The distance between the starts of two consecutive coils measured in terms of coil sides is called (a) front pitch (b) winding pitch (c) commutator pitch (d) back pitch
Last Answer : (b) winding pitch
Description : A current density of _____ is ilsed for large power transformers with forced circulation of oil or with water cooling coils (a) 1.5 to 2.5 A/mm2 (b) 3.5 to 4.5 A/mm2 (c) 4.0 to 5.0 A/mm2 (d) 5.4 to 6.2 A/mm2
Last Answer : (d) 5.4 to 6.2 A/mm2
Description : Dummy coil should not be used in (a) small machines (b) large machines (c) either (a) or (b) (d) none of the above
Last Answer : (b) large machines
Description : Which of the following is used for pumping crude oil from oil well? (A) Single stage centrifugal pump (B) Gear pump (C) Screw pump (D) Duplex/triplex reciprocating pump
Last Answer : (D) Duplex/triplex reciprocating pump
Description : The high voltage winding is usually which of the following type ? (a) Cylindrical winding with circular conductors (b) Cross-over winding with either circular or small rectangular conductors (c) Continuous disc type winding with rectangular conductors (d) All of the above types
Last Answer : (d) All of the above types
Description : The value of exciting or magnetizing current depends upon which of the following factors ? (a) Total m.m.f. required (b) The number of turns in the exciting winding (c) The way in which the winding is distributed (d) All of the above
Last Answer : (d) All of the above
Description : Direct water cooling of rotor winding presents (a) no mechanical difficulties (b) lesser mechanical difficulties (c) greater mechanical difficulties (d) none of the above
Last Answer : (c) greater mechanical difficulties
Description : cooling is the process of dissipating the armature and field winding losses to a cooling medium circulating within the winding insulation wall (a) Direct (b) Indirect (c) Conventional (d) Any ofthe above
Last Answer : (a) Direct
Description : The forced oil and air circulation method is usual one for transformers of capacities (a) upto 5 MVA (b) upto 10 MVA (c) upto 20 MVA (d) 30 MVA upwards
Last Answer : (d) 30 MVA upwards
Description : D.C. windings are (a) sometimes 2-layer type (b) never 2-layer type (c) always 2-layer type (d) none of the above
Last Answer : (c) always 2-layer type
Description : The purpose of providing dummy coils in a generator is?
Last Answer : The purpose of providing dummy coils in a generator is to provide mechanical balance for the rotor.
Description : The insulation between windings and grounded core and the insulation between the windings of the same phase is called (a) minor insulation (b) major insulation (c) either of the above (d) none of the above
Last Answer : (b) major insulation
Description : The time taken by the machine to attain 0.632 of its final steady temperature rise is called (a) heating time constant (b) cooling time constant (c) either (a) or (b) (d) none of the above
Last Answer : (a) heating time constant
Description : Machines cooled by direct cooling method may be called (a) "supercharged" (b) "inner cooled" (c) "conductor cooled" (d) any of the above
Last Answer : (d) any of the above
Description : In D.C. machines the number of slots per pole usually lies (a) between 2 to 4 (b) between 6 to 8 (c) between 9 to 16 (d) between 20 to 30
Last Answer : (c) between 9 to 16
Description : In D.C. machines the usual limit of slot pitch is (a) between 5 to 10 mm (b) between 10 to 15 mm (c) between 15 to 20 mm (d) between 25 to 35 mm
Last Answer : (d) between 25 to 35 mm
Description : Which of the following methods may be adopted to reduce the effects of armature reaction ? (a) Increase in length of air gap at pole tips (b) Increasing reluctance of pole tips (c) Compensating windings (d) Interpoles (e) All of the above
Last Answer : (e) All of the above
Description : The operation of a D.C. machine with large air gap lengths is comparatively (a) quiet (b) noisy (c) either of the above (d) none of the above
Last Answer : (a) quiet
Description : In D.C. machines, the ____ in field mmf results in increase in size and cost of machines. (a) increase (b) decrease (c) either of the above (d) none of the above
Last Answer : (a) increase
Description : In D.C. machines, ir order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made (a) equal to that of armature mmf (b) less in comparison with the arma¬ture mmf (c) large in comparison with the arma-ture mmf (d) none of the above
Last Answer : (c) large in comparison with the arma-ture mmf
Description : D.C. machines designed with a large value of air gap length have (a) worst, ventilation (b) poor ventilation (c) better ventilation (d) none of the above
Last Answer : (c) better ventilation
Description : In D.C. machines the width of the duct is usually (a) 4 mm (b) 6 mm (c) 8 mm (d) 10 mm
Last Answer : (d) 10 mm
Description : In a D.C. machine, the value of peripheral speed should not, normally, exceed (a) 10 m/s (b) 20 m/s (c) 30 m/s (d) 40 m/s
Last Answer : (c) 30 m/s
Description : In a D.C. machine the current per brush arm should not be more than (a) 100 A (6) 200 A (e) 300 A (d) 400 A
Last Answer : (d) 400 A
Description : In a D.C. machine the number of brush arms is _____ the number of poles. (a) less than (b) equal to (c) greater than (d) none of the above
Last Answer : (b) equal to
Description : The weight of copper of both armature and field windings decreases with _____ in number of poles. (a) increase (b) decrease (c) either of the above (d) none of the above
Description : Which of the following problem arises in D.C. motors which are fed from thyristor bridge circuits ? (a) Increased I R losses (b) Increased core losses (c) Poor commutation (d) Change in motor parameters (e) All of the above
Description : ________ is the common method of applying brushes to the commntator. (a) Radial (b) Trailing (c) Reaction (d) All of the above
Description : Which of the following brushes can be used for high values of current density ? (a) Metal graphite brushes (b) Hard carbon brushes (c) Electro-graphitic brushes (d) Natural graphite brushes
Last Answer : (a) Metal graphite brushes
Description : _____ brushes are fragile and cause excessive wear of commutator, (a) Natural graphite (b) Hard carbon (c) Electro graphitic (d) Metal graphite
Last Answer : (a) Natural graphite
Description : is usually used for brush rockers (a) Mild steel (b) Copper (c) Aluminium (d) Cast-iron
Last Answer : (d) Cast-iron
Description : The laminations of the armature of a D.C. machine are usually _____ thick. (a) 0.1 to 0.2 mm (b) 0.2 to 0.3 mm (c) 0.3 to 0.4 mm (d) 0.4 to 0.5 mm
Last Answer : (d) 0.4 to 0.5 mm
Description : The stator of a D.C. machine comprises of (a) main poles (6) interpoles (c) frame (d) all of the above
Last Answer : (d) all of the above
Description : D.C. servomotors are used in (a) purely D.C. control systems (6) purely AC. control systems (c) both D.C. and AC. control systems (d) none of the above
Last Answer : (a) purely D.C. control systems
Description : Which of the following in an application of D.C. motors? (a) Traction (b) Drives for process industry (c) Battery driven vehicles (d) Automatic control (e) All of the above
Description : The surge phenomenon is particularly important in case of (a) low voltage transformers (b) medium voltage transformers (c) high voltage transformers (d) any of the above
Last Answer : (c) high voltage transformers
Description : The cylindrical windings using circular conductors are used for current rating of (a) upto 20 A (b) upto 40 A (c) upto 60 A (d) upto 80 A
Last Answer : (d) upto 80 A
Description : A practical formula for determining the thickness of insulation between low voltage and high voltage windings is (a) 1 + 0.2 kVmm (6) 2 + 0.5 kVmm (c) 4 + 0.7 kV mm (d) 5 + 0.9 kV mm
Last Answer : (d) 5 + 0.9 kV mm
Description : Which of the following is the basic consideration in the design of insulation ? (a) Electrical considerations (b) Mechanical considerations (c) Thermal considerations (d) All of the above
Description : For large power transformers, self oil cooled type or air blast type which of the following values of current density may be used ? (a) 1.0 to 1.2 A/mm2 (b) 1.5 to 2.0 A/mm2 (c) 2.2 to 3.2 A/mm2 (d) 3.2 to 4.2 A/mm2
Last Answer : (c) 2.2 to 3.2 A/mm2
Description : For 275 kV transformers, using cold rolled grain oriented steel, which of the following values of flux density may be used? (a) 1.0 Wb/m2 (b) 1.1 Wb/m2 (c) 1.3 Wb/m2 (d) 1.6 Wb/m2 (e) None of the above
Last Answer : (d) 1.6 Wb/m2
Description : The usual values of maximum flux densities for distribution transformers using hot rolled silicon steel are (a) 0.5 to 0.8 Wb/m2 (b) 0.8 to 1.0 Wb/m2 (c) 1.1 to 1.35 Wb/m2 (d) 1.4 to 1.8 Wb/m2
Last Answer : (c) 1.1 to 1.35 Wb/m2
Description : The voltage control in electric supply networks in required on account of which of the following reasons ? (a) Adjustment of voltage at consumers premises within statutory limits (b) Control of ... daily and seasonal voltage variations in accordance with variations of load (d) All of the above
Description : The flash point of transformer oil should be higher than (a) 40°C (b) 60°C (c) 80°C (d) 104°C
Last Answer : (d) 104°C
Description : Transformers with a capacity of upto _____ have a cooling radiator system with natural cooling (a) 2 MVA (b) 5 MVA (c) 7.5 MVA (d) 10 MVA
Last Answer : (d) 10 MVA
Description : The heat dissipating capability of transformers of ratings higher than 30 kVA in increased by providing which of the following ? (a) Corrugations (b) Fins (c) Tubes (d) Radiator tanks (e) All of the above
Description : Disc windings are primarily used in (a) short capacity transformers (b) medium capacity transformers (c) high capacity transformers (d) any of the above
Last Answer : (c) high capacity transformers
Description : Multi-layer helical windings are commonly used in the transformers as high voltage windings (a) upto 20 kV (b) upto 50 kV (c) upto 80 kV (d) for 110 kV and above
Last Answer : (d) for 110 kV and above
Description : Helical windings are used in (a) distribution transformers (b) power transformers (c) shell type transformers (d) none of the above
Last Answer : (b) power transformers
Description : Cylindrical windings using circular conductors, employed in transformers, are (a) single layered (b) double layered (c) multi-layered (d) none of the above
Last Answer : (c) multi-layered