Steel Authority Of India Limited SAIL Model Questions Electrical Engineering Questions

Steel Authority Of India Limited
SAIL Model Questions
Electrical Engineering Questions

Q. In a D.generator, if the brushes are given a small amount of forward shift, the effect of
armature is

• Totally demagnetizing
• Totally magnetizing
• Partly demagnetizing and partly cross magnetizing
• Totally cross magnetizing

Q. The air gap between stator and armature of an electric motor is kept as small as possible

• To get a stronger magnetic field
• to improve the air circulation
• To reach the higher speed of rotation
• To make the rotation easier.

Q. Two series motors are coupled.One motor runs as generator and other as motor. The friction losses of the two machines will be equal when

• Both operates at same voltage
• Both have same back emf
• Both have same speed
• both have same excitation

Q. Plugging of D.motor is normally executed by

• Reversing the field polarity
• Reversing the armature polarity
• Reversing both the armature and field polarity
• Connecting a resistance across the armature.

Q. Transformer oil transformer provides

• Insulation and cooling
• Cooling and lubrication
• Lubrication and insulation
• Insulation, cooling and lubrication

Q. Leakage fluxes of transformer may be minimized by

• Reducing the magnetizing current to the minimum
• Reducing the reluctance of the iron core to the minimum
• Reducing the number of primary and secondary turn to the minimum
• Sectionalizing and interleaving the primary and secondary windings

Q. Electric power is transformed upon one coil to other coil in a transformer

• Electrically
• Electro Magnetically
• Magnetically
• Physically

Q. The most suitable and economical connection for small high voltage transformer is a

• Star- Delta connection
• Delta- Delta connection
• Delta- Star connection
• Star- Star connection

Q. An alternator is said to be over excited when it is operating at

• Unity power factor
• Leading power factor
• Lagging power factor
• Either lagging or leading power factor

Q. In an A.machine, the armature winding is kept stationary while the field winding is kept
rotating for the following reason

• Armature handles very large currents and high voltages
• Armature friction involving deep slots to accommodate large coils is easy if armature is kept stationary
• Ease of cooling the stator than rotor
• None of the above.

Q. In a synchronous motor, the torque angle is the

• Angle between the rotating stator flux and rotor poles
• Angle between the magnetizing current and back emf
• Angle between the supply voltage and back emf
• None of the above

Q. A 3-phase synchronous motor is said to be "floating" when it operates

• On no load and without loss
• On constantly varying load
• On pulsating load
• On high load and variable supply voltage

Q. Speed of synchronous motor depends upon

• Number of poles
• Supply frequency
• Both (a) and (b) 
• Neither (a) nor (b)

Q. Imbalance in the shaft of an induction motor occurs due to

• Slip rings
• Overheating of winding
• Non uniform of air gap
• Rigid construction

Q. Squirrel cage induction motor has

• Zero starting torque
• Very small starting torque
• Medium starting torque
• Very high starting torque

Q. The principle of operation of a 3-phase induction motor is similar to that of a

• Synchronous motor
• Repulsion - start induction motor
• Transformer with a shorted secondary
• Capacitor - start, induction - run motor

Q. The speed/load characteristics of a universal motor are similar to those

• D.shunt motor
• D.series motor
• A.motor
• None of the above

Q. Single phase A.motor generally used for vacuum cleaners is

• Universal motor
• Repulsion motor
• Hysteresis motor
• Reluctance motor

Q. Buchholz relay is used for the protection of

• Switch yard
• Transformers
• Alternators
• Transmission lines

Q. The type of braking used in traction system is

• Mechanical braking
• Electro - pneumatic braking
• Vacuum braking system
• All the above

Q. The function of processing zenger diode in a UJT circuit used for triggering of SCRs is to

• Expedite the generation of triggering pulses
• Delay the generation of triggering pulses
• Provide a constant voltage to UJT to prevent erratic firing
• Provide a variable voltage to UJT as the source voltage changes

Q. The frequency of a ripple in the output voltage of a 3 - phase semi converter depends upon

• Firing angle and load resistance
• Firing angle and supply frequency
• Firing angle and load inductance
• Only on load circuit parameters

Q. The SCR is turned off when the anode currents falls below

• Forward current rating
• Break - over voltage
• Holding current
• Latching

Q. V4 characteristics of emitter of a UJT is

• Similar to CE with linear and saturation region
• Similar to FET with a linear and pinch of region
• Similar to tunnel diode in some respects
• Linear between the peak point and valley point

Q. A transformer works on

• DC
• AC
• AC & DC both
• Neither AC not DC