Explore topic-wise MCQs in Electrical Engineering Questions.

In T-T connection, the percentage tapping of main transformer and teaser transformer are

A 4 pole, d.c. generator has a wave wound armature with 812 conductors. The flux per pole is 0.014 Wb. The speed at which it should be run to generate 240 V on no load is

A 4 pole, lap wound d.c. generators has 40 coils with 8 turns per coils. It is driven at 1200 rpm. If the flux per pole is 0.022 Wb, then the generated emf is

The rotational or stray losses includes

In a d.c. machine, the current rating and voltage rating of wave winding is

The rotational losses in d.c. machines is equal to the

For performing Hopkinson’s test two identical machines are required which are mechanically coupled. The iron losses in the two machines

Swinburne’s test and brake tests

The difference between field test and regenerative test is that

To have an induced emf in the d.c. generator, there should be relative motion between the conductor and flux. The plane of rotation and plane of flux

A 120 V d.c. shunt motor runs at speed of 1200 rpm. When the motor is operated unloaded but an additional resistance of 4 ohm is connected in series with the shunt field, then the speed increases and reaches to 1370 rpm with the same terminal voltage. The value of series resistance is

The most common method used to check for shorted windings is to perform

Out of different methods available for testing of d. c. motors, Swinburne’s test and Hopkinson’s test are commonly used in practice on

Consider three transformers connected in delta-delta fashion and supplying their rated load. Now if one of the transformer is removed then each of the remaining two transformer is overloaded. The overload on each transformer is given as

While performing Swinburne’s test, the iron losses are assumed to be

A 240 V, 17 kW d.c. shunt motor draws an armature current of 80 A at full load. The armature and shunt field resistances are 0.2 ohm and 195 ohm respectively. The rotational losses and efficiency of motor at full load is

While performing retardation tests, the machine whose test is to be taken is run at a speed which is

While carrying out brake tests if the belt snaps, then the motor will

A d.c. shunt generator delivers 190 A at a terminal voltage of 220 V. The copper losses and stray losses are 2000 W and 1000 W respectively. The efficiency of the generator is

The speed in d.c. machine can be measured by using

The hysteresis motor are mainly used in tape recorders because

The load carried by V - V connection is

A 120 V shunt generator running at 850 rpm has its armature and shunt field resistance of 0.15 ohm and 50 ohm respectively. It supplies 200 lamps each rated at 60 W, 100 V. The friction and windage and core loss of the machine is 400 W. its armature copper loss on full load and shunt field loss is

D.C. shunt motors are commonly used in

If the voltage supply of a single phase transformer is doubled and the supply frequency is halved, then the eddy current loss will become

In a three phase transformer, the current flowing in three primaries produces three corresponding fluxes. The sum of these three fluxes at any instant is

The constant voltage transformers are most commonly used in

In an autotransformer if the power transferred inductively is equal to the power conducted through, then transformation ratio is given by

With a bank of two single phase transformers connected in V - V fashion supplying a balanced three phase load with Cosφ as power factor. The power factor of the two transformers is given by

The average power factor at which V-V bank is operating is less than that with the load. The power factor is

In T-T connection, the ratio of actual capacity to the available capacity is

If a two winding transformer is converted into an autotransformer by applying additive polarity and subtractive polarity which results in the secondary voltages of 1840 and 1810 volts. Then the primary and secondary voltages of transformer are

Whether the given autotransformer is step up or step down, its VA rating is always

Compared to the two winding transformer, in an autotransformer the leakage reactance and copper losses is

A star connected three phase transformer is provided with tertiary delta connected winding which allows the flow of

In textile machines, to avoid breaking of threads, soft starters are used. The commonly used method in soft starter is

The stator of split phase induction motor has two windings, main winding and auxiliary winding. These windings are displaced in space by

A ferro resonant transformer regulation is also known as

In washing machines, most commonly used motors are

The spit phase induction motor has

Split phase induction motors are available in the range of

In capacitor start capacitor run induction motor, the capacitor remains in circuit

The capacitor connected permanently in capacitor run motor

The starting torque and power factor of shaded pole induction motor

In shaded pole induction motor, direction of rotation of magnetic field is from non shaded pole to shaded pole

A 3 phase induction motor in a short circuit current is equal 3 times of the full load current. If the full load slip is 2%, then the starting torque as a percentage of full load torque is

While conducting the sumpner’s test, the primaries of the two identical transformers are connected in parallel across the supply. The secondary’s are connected in

If W1 is the input power measured by the wattmeter connected across the primaries and W2 is the measurement of wattmeter connected in secondary’s while performing sumpner’s test then iron losses and copper losses is equal to

In sumpner’s test, the net voltage in the local circuit of secondary’s is

If the power factor of a transformer increases, then its efficiency will