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Organisation : Delhi Metro Rail Corporation Ltd
Post : Junior Engineer Electrical
Document Type : Sample Question Paper
Website : delhimetrorail.com

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Junior Engineer Electrical Sample Paper :

TECHNICAL APTITUDE :
In a three-phase induction motor, the rotor field runs at the following speed with respect to the stator structure:
(1) At synchronous speed in the direction of stator field
(2) At a slip speed in the direction of stator speed
(3) At synchronous speed in a direction opposite to that of stator field
(4) At zero speed

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V/f is maintained constant in the following case of speed control of induction motor
(1) Below base speed with voltage control
(2) Below base speed with frequency control
(3) Above base speed with frequency control
(4) None of these

In a double-cage induction motor, which of the following is not true
(1) Resistance of outer bar is less
(2) Leakage inductance of outer cage is less
(3) Outer bar has smaller cross section
(4) None of these

The voltage regulation of a transformer at full load 0.9 p.f. lagging is 5%. For a full load at 0.9 p.f. leading, it will
(1) Remain the same
(2) Become negative
(3) Reduce and may even become negative
(4) Increase

For which of the following pair of machines, the stator and its winding can be of the same type
(1) Universal motor and stepper motor
(2) D.C. motor and hysteresis motor
(3) Hysteresis motor and reluctance motor
(4) Induction motor and D.C. motor

In which of the following amplifier configurations, the power gain is the largest?
(1) Common-Emitter
(2) Common-Collector
(3) Common-Base
(4) None of these

Transformer core is laminated in order to
(1) Decrease copper losses
(2) Decrease entire core losses
(3) Decrease only eddy current losses
(4) Decrease only hysteresis losses

For increasing the range of voltmeter, one should connect a
(1) High value resistance in series with voltmeter
(2) Low value resistance in series with voltmeter
(3) High value resistance in parallel with voltmeter
(4) Low value resistance in parallel with voltmeter.

To conduct Sumpners test on a transformer
(1) Only one transformer is sufficient
(2) Two identical transformers are needed
(3) Two un-identical transformers are needed
(4) At least three transformers are necessary

Unit of reactive power is
(1) Watt
(2) Kilo watt
(3) Var
(4) Volt ampere

Synchronous Generator is a source of
(1) Real Power
(2) Reactive power
(3) Apparent power
(4) Both real and reactive power

In an induction motor, if the air gap is increased,:
(1) Speed will reduce
(2) Efficiency will improve
(3) Power factor will be lowered
(4) Breakdown torque will reduce

A DC shunt motor is running at 1200 rpm, when excited with 220V dc. Neglecting the losses and saturation, the speed of the motor when connected to a 175 V supply is:
(1) 70 rpm
(2) 900 rpm
(3) 1050 rpm
(4) None of these

The function of oil in a transformer is to provide:
(1) Insulation and cooling
(2) Protection against lighting
(3) Protection against short circuit
(4) Lubrication

The ratio of starting torque to running torque in a synchronous motor is:
(1) Zero
(2) One
(3) Two
(4) Infinity

A Q– meter measures
(1) Loss in a capacitor
(2) Frequency
(3) Accurate value of electrical quantity
(4) Properties of the coils

The hysteresis Motor
(1) Has a D.C. winding on the rotor
(2) Rotor is made out of hard magnetic material
(3) Has squirrel-cage winding on the rotor
(4) Is not-self starting

Counterpoise is used for
(1) Transformer earthing
(2) Reducing transmission tower footing resistance
(3) Generator earthing
(4) Motor earthing

A single–phase ac regulator is used to convert
(1) Fixed ac voltage to variable magnitude ac voltage of same frequency
(2) Fixed ac voltage to variable frequency ac voltage of same magnitude
(3) Fixed ac voltage to variable frequency ac voltage through dc link
(4) Fixed ac voltage to variable magnitude variable frequency ac voltage

In a 3–phase voltage source inverter used for speed control of induction motor, anti–parallel diodes are used across each switching device. The main purpose of diodes is to
(1) Protect the switching devices against over voltage
(2) Provide path for freewheeling current
(3) Allow the motor to return energy during regeneration
(4) Help in switching off the devices

The pressure coil of a wattmeter consists of
(1) More number of turns of fine wire
(2) Less number of turns of fine wire
(3) Less number of turns of thick wire
(4) More number of turns of thick wire.