Interview Questions.

Q1. What Is A Commutator?

The commutator is a tool which converts alternating induced emf in a generator to DC emf. In case of motor it produces unidirectional torque.

Q2. What Are The Conditions To Be Satisfied For Parallel Operation Of Dc Generators?

The polarities of the mills have to be equal or the connections should be interchanged until they end up identical.

The voltages of each the mills should be same.

The change of voltage with change of load should be of equal individual.

The top movers riding the turbines need to have stable and comparable rotational pace characteristics.

The nice and terrible terminals of mills need to be connected nicely to the high-quality and poor of busbar.

Q3. What Are The Major Parts Of The Dc Generators?

Yoke Poles

Field winding

Armature

Armature winding

Commutator brushes

Q4. What Are The Applications Of Electric Motor?

Electric vehicles applications are: business f, blowers and pumps, gadget gear, family appliances, electricity equipment, and disk drives, record players.

Q5. What Is Meant By Reactance Voltage?

An armature coil has certain self inductance.

When coil undergoes commutation, there is change in modern-day (di) in that coil and the commutation takes certain time(dt).

Thus there's self-brought about emf in a coil present process commutation given by means of L(di/dt).

This EMF induced in the coil present process commutation is referred to as reactance voltage.

Q6. What Is Universal Motor?

A series-wound motor is referred to as a typical motor whilst it has been designed to function on both AC or DC electricity. It function nicely on AC because the current in each the sphere and the armature (and hence the ensuing magnetic fields) will exchange in synchronism and as a result, the ensuing mechanical pressure will arise in a constant route of rotation.

Q7. What Are The Advantages Of Stationary Armature And Rotating Field System?

The stationary armature coils can be insulated without difficulty.

Higher peripheral velocity can be achieved within the rotor.

Cooling of the winding is more efficient.

Only  slip earrings are required to offer DC deliver to the sphere device

Output current may be without difficulty furnished to the burden circuit. Slip-rings and brushes aren't important.

Q8. What Is Basic Principle Of Operation Of Alternators/dc Generators?

They are running on the essential principle based totally on Faraday’s Laws of Electromagnetic Induction.

This regulation states that, When a modern carrying conductor moves in magnetic discipline, it induces an EMF.

Q9. What Is Ac Motor?

An AC motor is an electric powered motor driven by an alternating cutting-edge (AC). It normally consists of two simple components, an out of doors stationary stator having coils furnished with alternating modern to supply a rotating magnetic area, and an internal rotor connected to the output shaft that is given a torque with the aid of the rotating area.

Q10. What Are The Advantages And Disadvantages Of Ac, Dc Motors?

Advantages of AC Motors:

Low fee,

lengthy lifestyles,

excessive efficiency,

large ratings available (to one MW or greater),

massive variety of standardized sorts.

Disadvantages of AC Motors:

Starting inrush present day may be excessive,

pace manipulate requires variable frequency source.

Advantages of DC Motors:

Precision positioning,

High preserving torque,

Long lifespan,

Low protection,

High efficiency

Disadvantages of DC Motors:

Some can be pricey,

Require a controller,

Higher preliminary price,

Requires a controller.

Q11. What Are The Advantages Of Three Phase Motor Over Single Phase Motor?

Three phase vehicles are having

Higher starting torques

Improved speed regulation

Less vibration

Quieter operation

compared to the unmarried section motors.

Q12. What Is Meant By Turbo Alternators?

Turbo alternators are excessive pace alternators. Because of high speed of rotation, the rotor diameter is decreased and the axial length is multiplied. Two or four poles are usually used and steam generators are used as top movers.

Q13. Will The Alternators Have Rotating Armature System Or Stationary Armature System?

Generally in alternators, the armature is desk bound and the sector rotates. Small low-voltage alternators often have a rotating armature and a stationary area winding.But in huge alternators rotating armature field kind is used.

Q14. Define Pole Pitch?

The distance between the centres of  adjoining poles is known as pole pitch. One pole pitch is equals to 180 electric tiers. It is likewise defined as the variety of slots consistent with pole.

Q15. Why Is The Efficiency Of A Three-phase Induction Motor Is Less Than That Of A Three-phase Trformer?

Three segment Induction motor is nothing but a rotating trformer.

Due to rotating nature, there are friction and windage losses related to it.

On the opposite hand, the three-section trformer is a static tool, for that reason there are not any rotational losses.

Thus the performance of 3-segment induction motor is less than that of a three-phase trformer.

Q16. What Is Meant By Short Pitched Winding?

If the coil span is less than the pole pitch, the winding is known as as shot-pitched winding. It is also referred to as short-chorded winding.

Q17. Why The Air Gap Between The Pole Pieces And The Armature Is Kept Very Small?

The air hole among the pole portions and the armature is stored very small to hold the sphere power at its highest cost.

This is due to the cause the flux lines can pass thru iron very easily than the air hole.

The small air hole generates excessive voltage.

Larger the air hole me more potent need to be the magnetising pressure to provide the specified voltage consequently the air hole is stored very small.

Q18. What Are The Various Types Of Rotors Used In The Alternators?

Salient pole rotor

Non- salient pole rotor and Cylindrical rotor

Q19. What Is Meant By Full Pitched Winding?

If the coil span is equal to pole pitch, the winding is referred to as as complete pitched winding.

Q20. What Is Electric Motors?

An electric motor is an electrochemical tool that converts electric energy into mechanical electricity. Most electric automobiles perform thru the interplay of magnetic field and current carrying conductors to generate pressure.

Q21. Define Coil Span?

The distance among the two coil facets of a coil is referred to as as coil span. It may be expressed in electric tiers or in number of slots.

Q22. What Is The General System Requirements Of Alternator?

For the era of emf, there have to be  basic systems.

Magnetic discipline device to supply the magnetic field

Armature machine which homes the conductors on which the EMF is to be caused.

Q23. Why Does Curving The Pole Faces In A Dc Machines Contributes To A Smoother Dc Output Voltage From It?

For having smoother output voltage from DC machines its commutation have to be as best as possible.

In order to have true commutation the flux density within the air hole should lower steadily from maximum value beneath the centre of the pole to 0 on.

Q24. On What Principle Electric Motor Works?

The Motor Principle: while a present day-wearing conductor is located in an external magnetic field perpendicular to the conductor, the conductor stories a force perpendicular to itself and to the outside magnetic area.The bodily precept in the back of production of mechanical force via the interactions of an electric powered cutting-edge and a magnetic field.

The proper-hand rule for pressure on a conductor may be used to decide the route of the pressure skilled at the conductor.

Q25. What Are The Advantages And Disadvantages Of Short-pitched Winding?

The blessings are:

They save copper for give up connections

They improve the waveform of the generated EMF.

The generated EMF may be made to approximate to a sine wave greater effortlessly and the distorting harmonics may be reduced.

The risks are:

The general voltage around the coils is some what reduced. Because the voltage induced within the  coil sides are slightly out of section.

Q26. How Many Types Of Electric Motors Are There?

Mainly there are  sorts of electric automobiles:

AC motors

DC motors

Q27. What Is Meant By Stator? What Is Meant By Rotor?

In any electric gadget ( AC/DC motor or generator) the stationary member is called as stator. Similarly in all machines the rotating member is referred to as rotor.

Q28. The Series Field Winding Has Low Resistance While The Stunt Field Winding Has High Resistance. Why?

The series filed winding is always related in series with the armature and accordingly has to carry the armature modern which immediately receives determined by way of the load.

Thus the modern-day passing through collection area winding is of high degree.

The voltage drop across collection area winding receives delivered to the voltage drop across armature winding at the same time as deciding the back emf. This voltage drop need to be very small.

Hence as the modern via series subject winding is excessive, to be able to maintain voltage drop throughout it to a small value, its resistance may be very low.

On the alternative hand, the shunt subject winding is at once linked across the rated supply voltage for this reason to limit present day through it, resistance could be very excessive.

Q29. How To Minimize The Eddy Current Losses?

When the middle is laminated and insulated from every different with paper or varnish the eddy contemporary loss is minimized.

Q30. What Is Dc Motors?

A DC motor is a automatically commutated electric powered motor powered from direct current (DC). The stator is stationary in area by definition and therefore so is its contemporary. The present day inside the rotor is switched by using the commutator to additionally be stationary in space. This is how the relative attitude between the stator and rotor magnetic flux is maintained near ninety degrees, which generates the maximum torque.