Electrical machines having a power output upto about 750 W may be
called_______machines.
(a) small size
(b) medium size
(c) large size
(d) any of the above

1 Answer

Answer :

(a) small size

Related questions

Description : Electrical machines having power outputs ranging from a few kW upto approximately 250 kW may be classified as (a) small size machines (b) medium size machines (c) large size machines (d) any ofthe above

Last Answer : (b) medium size machines

Description : In ______ machines, the size of the shaft is decided by the critical speed which depends on the deflection of the shaft. (a) small (b) medium (c) large (d) any of the above.

Last Answer : (c) large

Description : Commercial available medium size machines have a speed range of ______ . (a) 200 to 400 r.p.m. (b) 600 to 1000 r.p.m. (c) 1000 to 1500 r.p.m. (d) 2000 to 2500 r.p.m.

Last Answer : (d) 2000 to 2500 r.p.m.

Description : Multiple inlet system of air cooling of turbo-alternators can be used for machines of rating upto (a) 10 MW (b) 30 MW (c) 60 MW (d) 150 MW

Last Answer : (c) 60 MW

Description : Aluminium when adopted as a conductor material in ______ transformers, decreases the overall cost of the transformer (a) small size (b) medium size (c) large size (d) any of the above size

Last Answer : (a) small size

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 : The design of mechanical parts is particularly important in case of _____ speed machines. (a) low (b) medium (c) high (d) any of the above

Last Answer : (c) high

Description : is universally used for windings of electrical machines because it is easily workable without any possibility of fracture. (a) Silver (b) Steel (c) Aluminium (d) Copper

Last Answer : (d) Copper

Description : Yokes with rectangular cross-section are used for (a) small capacity transformers (b) medium capacity transformers (c) large capacity transformers (d) any of the above

Last Answer : (a) small capacity transformers

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 ____ 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 : 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 : 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 : 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 : 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 : 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 : 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 : 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 : 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 : The action of electromagnetic machines can be related to which ofthe following basic principles ? (a) Induction (b) Interaction (c) Alignment (d) All of the above

Last Answer : (d) 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 : 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 : 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 noise produced by a ______ cooled machine is less as the rotor moves in a medium of smaller density. (a) air (b) hydrogen (c) either (a) or (b) (d) none of the above

Last Answer : (b) hydrogen

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 : 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

Last Answer : (d) All of the above

Description : The heated parts of an electrical machine dissipate heat into their surroundings by which of the following modes of heat dissipation ? (a) Conduction (b) Convection (c) Radiation (d) All ofthe above

Last Answer : (d) All ofthe above

Description : In induction motors, the length of air gap in kept as small as mechanically possible is order to have (a) low power factor (b) high power factor (c) high over load capacity (d) any of the above

Last Answer : (b) high power factor

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 : Which ofthe following materials is used in the manufacture of resistance grids to be used in the starters of large motors ? (a) Copper (b) Aluminium (c) Steel (d) Cast-iron

Last Answer : (d) Cast-iron

Description : Which ofthe following is an advantage of hydrogen cooling ? (a) Increase in efficiency (b) Increase in ratings (c) Increase in life (d) Smaller size of coolers (e) All ofthe above

Last Answer : (e) All ofthe above

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 : 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 : 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 : By which of the following methods the temperature rise of windings and other parts may be determined ? (a) Thermometer method (6) Resistance method (c) Embedded temperature detector method (d) Any of the above

Last Answer : (d) Any of the above

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

Last Answer : (d) All of the 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 : Power transformers should be designed to have maximum efficiency (a) at one-fourth load (b) at one-half load (c) at or near full load (d) any of the above

Last Answer : (c) at or near full load

Description : Power transformers have rating (a) equal to 50 kVA (6) equal to 100 kVA (c) above 200 kVA (d) none of the above

Last Answer : (c) above 200 kVA

Description : Which of the following methods is most accurate ? (a) Equivalent current method (b) Equivalent power method (c) Equivalent torque method (d) Method of average losses

Last Answer : (a) Equivalent current method

Description : Which of the following methods does not take into account the maximum temperature rise under variable load conditions ? (a) Equivalent power method (b) Equivalent current method (c) Method of average losses (d) Equivalent torque method

Last Answer : (c) Method of average losses

Description : By which of the following methods motor rating for variable load drives can be determined ? (a) Method of average losses (b) Equivalent current method (c) Equivalent torque method (d) Equivalent power method (e) All of the above.

Last Answer : (e) All of the above.

Description : On which of the following variables heat convected depends ? (a) Power density (b) Temperature difference between heated surface and coolant (c) Thermal resistivity, density, specific heat (d) Gravitational constant (e) All ofthe above

Last Answer : (e) All ofthe above

Description : The length cf air gap to be provided in ______ is primarily determined by power factor consideration. (a) d.c. series motor . (b) d.c. shunt motor (c) induction motor (d) synchronous motor

Last Answer : (c) induction motor

Description : impose limitation on design. (a) Saturation (b) Temperature rise (c) Efficiency (d) Power factor (e) All above

Last Answer : (e) All above

Description : Mechanisation in india at various levels can be done in following ways a) by introducing the improved agricultural implements on small scale holding to be operated by bullocks. b) by using small ... tractor and machines on remaining holding to supplement animal power source. d) All of the above

Last Answer : All of the above

Description : A two stroke engine has a speed of 750 rpm. A four stroke engine having an identical cylinder size runs at 1500 rpm. The theoretical output of the two stroke engine will (a) Be twice that of the four stroke ... ) Be the same as that of the four stoke (d) Depend upon whether it is a CI or SI engine

Last Answer : Ans :c

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