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The correct answer is (B) 6

Best explanation: There are 6 DESIGN steps INVOLVED in the design of the ROTOR. They are number of rotor slots, area of rotor bars, area of end rings, rotor resistance, rotor teeth, rotor core.

Right answer is (c) flux density in STATOR CORE = maximum flux / 2 *length of the iron * depth of stator core

The EXPLANATION is: The maximum flux, length of iron and depth of stator core is CALCULATED. On substitution it provides the flux density in stator core.

Correct answer is (B) false

To ELABORATE: The flux density of the stator core should not exceed 1.5 weber per m^2. The range LIES between 0.9 – 1.4 weber per m^2.

Correct option is (a) true

To elaborate: The flux density of the general purpose MACHINE is 1.45 weber PER m^2. The flux density of the high TORQUE machines is 1.8 weber per m^2.

The correct option is (c) area REQUIRED for the insulated conductors = total number of conductors per slot * 0.785 * diameter of insulated conductor^2

Best EXPLANATION: The total number of conductors per slot and the diameter of insulated conductors are CALCULATED. On substitution the area required for the insulated conductors are calculated.

Correct choice is (c) LARGE number of slots, small leakage REACTANCE

Easy EXPLANATION: The number of slots is indirectly proportional to the leakage reactance. The LARGER the number of slots, the lower willbe the leakage reactance.

The correct option is (b) 3-4 A per mm^2

Easy explanation: The minimum value of the current density for the OPEN type MOTORS split phase, capacitor and repulsion START motors is 3 A per mm^2. The MAXIMUM value of the current density for the open type motors split phase, capacitor and repulsion start motors is 4 A per mm^2.

The CORRECT answer is (c) 8

Easiest explanation: There are 8 design DATA available in the design of the stator. The design data are RUNNING winding, number of TURNS In running winding, running winding conductors, number of stator slots, size of stator slot, stator teeth, stator core, length of mean turn.

The correct choice is (d) MEAN pitch FACTOR = pitch factor of each COIL PER pole group * turns in the coil / total number of turns

For explanation I WOULD say: The pitch factor of each coil per pole group, turns in the coil and total number of turns are obtained. On substitution, it gives the mean pitch factor.

The correct answer is (d) 3 or more

The best I can explain: The STATOR windings of single phase induction motors are CONCENTRIC type. There are USUALLY 3 or more coils PER pole each having same or DIFFERENT number of turns.

The CORRECT OPTION is (C) 70%

Easiest explanation: 70% of the total slots are used for the reduction of the mmf WAVE harmonics. The remaining 30% are used for accommodating the starting windings.

Right option is (c) concentric

The best I can explain: The STATOR windings are also known as the RUNNING winding or the MAIN winding. The TYPE of stator winding used is concentric type

Right option is (d) 0.35-0.55 WEBER per m^2

The explanation is: The minimum VALUE of the AVERAGE FLUX density is 0.35 weber per m^2. The maximum value of the average flux density is 0.55 weber per m^2.

The CORRECT choice is (c) 0.57

The best I can explain: The efficiency of the output watt of 37 is 0.38 and the efficiency of output watt of 90 is 0.48. The efficiency of the output watt of 180 is 0.57.

Right CHOICE is (b) 5:7

For EXPLANATION: The EFFICIENCY of the 75 watt motor is 50%. The efficiency of the 750 watt motor is 70%.

Correct choice is (c) kVA INPUT = horse power * 0.746 / EFFICIENCY * power factor

The explanation is: The horse power rating of the MACHINE along with the efficiency and power factor is calculated. On substitution the kVA input can be obtained.

Correct answer is (b) output coefficient = 11 * WINDING space FACTOR* specific magnetic loading * specific electric loading * 10^-3

The explanation is: The winding space factor, specific magnetic loading, specific electric loading is calculated. On substitution gives the output coefficient USED for the calculation of output equation.

Correct answer is (a) true

The explanation: Modern capacitor start motors employ ac ELECTROLYTIC capacitors. The ac electrolytic capacitor is formed by WINDING two sheets of etched ALUMINIUM foil, separated by two layers of insulating PAPER, into a cylindrical SHAPE.

Correct choice is (c) centrifugal operation and mechanical operation

To elaborate: The STARTING switch is used to cut the auxillary winding when the motor ATTAINS 75% of the full load SPEED. The switches operate in both the centrifugal as well as mechanical operation.

The CORRECT choice is (b) concentric WINDING

To explain I would say: The concentric winding is the most widely used winding. It is also the most flexible winding of the windings used in the SINGLE phase induction motor.

Right option is (b) SINGLE LAYER diamond coil windings

Easy explanation: The PROGRESSIVE windings is one KIND of the stator windings. They are in the FORM of the single layer diamond coil windings.

The correct CHOICE is (B) 3

The explanation: There are BASICALLY 3 KINDS of single phase windings. They are concentric, progressive and skein.

Right answer is (d) circular COILS

To explain: The SLOTS house the starting and running WINDINGS. The single phase INDUCTION motors are generally wound with CONCENTRIC coils.

The correct option is (C) 5

For explanation I would say: There are 5 steps in the construction of the single phase INDUCTION motor. They are stator, stator windings, rotor, STARTING switches, electrolytic capacitor.

Correct choice is (c) 0.2-0.3

The EXPLANATION is: The RANGE of starting TORQUE in the capacitor induction MOTOR is 2-3.5 and that of the repulsion start induction motor is 2-4. The range of the starting torque of the shaded pole induction motor is 0.2-0.3.

Right choice is (B) 4–6

Easiest explanation: The range of STARTING current is 5-7 for resistor type INDUCTION motor and that of the repulsion start motor is 2-3. The range of the starting current of capacitor induction motor is 4-6.

The correct option is (a) 0.37-50

Easy explanation: The range of output WATT for CAPACITOR TYPE induction MOTOR is 90-750 and that of the repulsion start motor is 90-3700. The range of output watt for resistor type induction motor is 7.5-370 and that of the shaded pole type is 0.37-50.

The CORRECT answer is (c) cage winding is replaced by commutator WINDINGS

For explanation: The REPULSION motor STARTING METHOD is one of the methods used in the starting of the single phase induction motor. Here the cage winding is replaced by the commutator windings.

The correct answer is (B) when high starting torque is REQUIRED

For explanation: The repulsion MOTOR starting METHOD is one of the 3 methods of starting the single phase induction motor. It is used when the high starting torque is required.

The correct ANSWER is (a) for outputs below 60 watt

Easy explanation: The EFFICIENCY of the shaded pole starting METHOD is very low. The shaded pole starting method is USED for outputs below 60 WATTS.

Correct CHOICE is (c) displacement between shaded and unshaded portion varies between 20°-30°

For EXPLANATION I would say: The shaded POLE starting METHOD is that the part of the pole is shaded by short CIRCUITED copper ring. The displacement between shaded and unshaded portion varies between 200-300.

Correct answer is (b) PART of the POLE is SHADED by short circuited copper RING

Explanation: One of the starting methods of the single phase induction motor is the shaded pole starting method. Here the part of the pole is shaded by the short circuited copper ring.

Right choice is (B) when the motor speed reaches 75 % of the full load speed

To explain: The single PHASE induction motor is not a SELF starting machine and hence starting WINDINGS are connected in series with the running winding. The starting windings are CUT out when the motor speed reaches 75 % of the full load speed.

The correct CHOICE is (d) by CONNECTING a suitable impedance

Explanation: The running winding displaces the starting winding by 90°. The required PHASE displacement is obtained by connecting a suitable impedance in SERIES with any of the WINDINGS.