Electrical Machine Design

Commercial available medium size machines have a speed range of ______ .

The usual values of maximum flux densities for distribution transformers using hot rolled silicon steel are

The electrical power to a meggar is provided by

In D.C. machines, ir order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made

Various adjustments in an energy meter include

For large power transformers, self oil cooled type or air blast type which of the following values of current density may be used?

The rectifier instrument is not free from

Instrument transformers are

In order to achieve high accuracy, the slide wire of a potentiometer should be

In D.C. machines the number of slots per pole usually lies

Which of the following methods is most accurate ?

________ has a lowrelative permeability and is used principally in field frames when cost is of primary importance and extra weight is not objectionable.

________ is the common method of applying brushes to the commntator.

Yokes with rectangular cross-section are used for

Which of the following meters are not used on D.C. circuits

Power transformers have rating

Which of the following is the basic consideration in the design of insulation ?

For measuring a very high resistance we should use

Commonly used instruments in power system measurement are

Is universally used for windings of electrical machines because it is easily workable without any possibility of

A current density of _________ is used for large power transformers with forced circulation of oil or with water cooling coils.

The resistance in the circuit of the moving coil of a dynamometer wattmeter should be

_______ brushes are fragile and cause excessive wear of commutator,

To avoid the effect of stray magnetic field in A.C. bridges we can use

It is required to measure the true open circuit e.m.f. of a battery. The best device is

Hydrogen has a heat transfer co-efficient _____ times that of air

The thermal conductivity of hydrogen is ______ times that of air

The design of mechanical parts is particularly important in case of _____ speed machines.

A voltage of about 200 V can be measured

Which of the following is measured by using a vector voltmeter ?

The heated parts of an electrical machine dissipate heat into their surroundings by which of the followingmodes of heat dissipation ?

The action of electromagnetic machines can be related to which of the following basic principles ?

Which of the following properties a damping oil must possess ?

In transformers using hot rolled steel, the cross-section of the yoke is made about _____ greater than that of the core

An induction meter can handle current up to

_______ is extensively used for those portions of magnetic circuit which carry steady flux and need superior mechanical properties ?

In a vibrating reed frequency meter the natural frequencies of two adjacent reeds have a difference of

Multiple inlet system of air cooling of turbo-alternators can be used for machines of rating upto

The household energy meter is

The flash point of transformer oil should be higher than

Dummy coil should not be used in

Which of the following essential features is possessed by an indicating instrument ?

Multilayer helical windings are commonly used in the transformers as high voltage windings

Impose limitation on design.

The surge phenomenon is particularly important in case of

Cylindrical windings using circular conductors, employed in transformers, are

The ratio of maximum displacement deviation to full scale deviation of the instrument is called

The pointer of an indicating instrument should be

Electrical machines having a power output up to about 750 W may be called_______machines.

The heat dissipated by from a surface depends upon its temperature and its characteristics like colour, roughness etc.

The length of air gap to be provided in ______ is primarily determined by power factor consideration.

Most common form of A.C. meters met with in every day domestic and industrial installations are

Hot rolled sheets have ______ value of permeability

An ammeter is a

An ohmmeter is a

In a Weston synchronoscope, the fixed coils are connected across

The time taken by the machine to attain 0.632 of its final steady temperature rise is called

With direct water cooling it is possible to have ratings of about

In induction motors, the length of air gap in kept as small as mechanically possible is order to have

Which of the following methods does not take into account the maximum temperature rise under variable loadconditions ?

Materials exhibiting zero value of resistivity are known as ______ .

Disc windings are primarily used in

Resistances can be measured with the help of

If an inductance is connected in one arm of bridge and resistances in the remaining three arms

A sensitive galvanometer produces large deflection for a

Alternating current is measured by

A universal RLC bridge uses

Is an instrument which measures the insulation resistance of an electric circuit relative to earth and one another,

are always double layer type.

The mcrease in heat dissipation by air blasts is due to increase in

If an insulating material is operated beyond the maximum allowable temperature, its life is

Which of the following materials is used in the manufacture of resistance grids to be used in the starters of largemotors ?

Two holes in the disc of energy meter are drilled at the opposite sides of the spindle to

Standard resistor is made from

A dynamometer wattmeter can be used for

An induction wattmeter can be used for

Basically a potentiometer is a device for

A potentiometer may be used for

When the two coil sides forming a coil are spaced exactly one pole pitch apart they are said to be of

Which of the following methods may be adopted to reduce the effects of armature reaction?

A Weston frequency meter is

A _____ device prevents the oscillation of the moving system and enables the latter to reach its final position quickly

In D.C. machines, the ________ in field mmf results in increase in size and cost of machines.

For measurement of mutual inductance we can use

In a low power factor wattmeter the compensating coil is connected

Which of the following devices may be used for extending the range of instruments ?

The operating voltage of a meggar is about

Which of the following brushes can be used for high values of current density ?

Which of the following is an advantage of hydrogen cooling?

The insulation between windings and grounded core and the insulation between the windings of the same phase is

Murray loop test can be used for location of

The laminations of the armature of a D.C. machine are usually _____ thick.

For measurement of inductance having high value, we should use

D.C. servomotors are used in

A power factor meter has

Helical windings are used in

Transformers with a capacity of up to _____ have a cooling radiator system with natural cooling

In a single phase power factor meter the phase difference between the currents in the two pressure coils is

In self cooled motors the cooling time constant is about ______ than the heating time constant because cooling conditions are worse at standstill.

The power of a n-phase circuit can be measured by using a minimum of

In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero. The power factor of the load must be

Wattmeter cannot be designed on the principle of

To measure a resistance with the help of a potentiometer it is

A Weston synchronoscope is a

The density of hydrogen is _____ times the density of air.

In D.C. machines the width of the duct is usually

The efficiency of a machine should be as ______ as possible to reduce the operating cost.

Which of the following methods is used for air cooling of turbo-alternators ?

In a Weston frequency meter, the magnetic axes of the two fixed coils are

A practical formula for determining the thickness of insulation between low voltage and high voltage windings is

The weight of copper of both armature and field windings decreases with _____ in number of poles.

Which of the following instruments indicate the instantaneous value of the electrical quantity being measured at the time at which it is being measured ?

In Weston synchronoscope the moving coil is connected across

The winding where dummy coils are used is sometimes called

By which of the following methods the temperature rise of windings and other parts may be determined ?

In a dynamometer 3-phase power factor meter, the planes of the two moving coils are at

With conventional hydrogen cooling it is possible to increase the rating of a single unit to

Which of the following is the commonly used type of electromagnets ?

The noise produced by a ______ cooled machine is less as the rotor moves in a medium of smaller density.

If the current in a capacitor leads the voltage by 80°, the loss angle of the capacitor is

The scale of a rectifier instrument is

Which of the following in an application of D.C. motors?

Most sensitive galvanometer is

Direct water cooling of rotor winding presents

According to application, instruments are classified as

Tractive magnets are operated from

If an instrument has cramped scale for larger values, then it follows

The resistivity of water should not be less than

In a D.C. machine the current per brush arm should not be more than

The power factor of a single phase load can be calculated if the instruments available are

The switch board instruments

The heat dissipating capability of transformers of ratings higher than 30 kVA in increased by providing which of the following?

The distance between the starts of two consecutive coils measured in terms of coil sides is called

In a 3-phase power measurement by two wattmeter method, both the watt meters had identical readings. The power factor of the load was

E.m.f. of a Weston cell is accurately measured by

D.C. windings are

The design of electromagnets is based upon which of the following fundamental equations ?

The disc of an instrument using eddy current damping should be of

For 275 kV transformers, using cold rolled grain oriented steel, which of the following values of flux density may be used?

________ cooling is the process of dissipating the armature and field winding losses to a cooling medium circulating within the winding insulation wall

The slot leakage can be calculated by making which of the following assumptions ?

The stator of a D.C. machine comprises of

Electrical machines having power outputs ranging from a few kW up to approximately 250 kW may be classified as

In an Anderson bridge, the unknown inductance is measured in terms of

The desirable static characteristics of a measuring system are

A moving iron instrument can be used for

Machines cooled by direct cooling method may be called

In D.C. machines the usual limit of slot pitch is

In majority of instruments damping is provided by

_______ instruments are those which measure the total quantity of electricity delivered in a particular time.

D.C. machines designed with a large value of air gap length have

_________ electromagnets generally function as holding magnets.

By which of the following methods motor rating for variable load drives can be determined ?

In direct cooled system using hydrogen both stator and rotor conductors are made

On which of the following variables heat convected depends ?

An instrument transformer is used to extend the range of

The value of exciting or magnetizing current depends upon which of the following factors ?

The voltage control in electric supply networks in required on account of which of the following reasons ?

The function of shunt in an ammeter is to

A phase shifting transformer is used in conjunction with

In a Schering bridge the potential of the detector above earth potential is

Induction type single phase energy meters measure electric energy in

To measure radio frequency, the suitable frequency meter is

The cold rolled grain oriented steel has ______ permeability in the direction of the grain orientation.

Power transformers should be designed to have maximum efficiency

are used for construction of core of electromagnets.

For measurements on high voltage capacitors, the suitable bridge is

A moving-coil permanent-magnet instrument can be used as flux meter

In ______ machines, the size of the shaft is decided by the critical speed which depends on the deflection of the shaft.

is usually used for brush rockers

A direct current can be measured by

The gravity controlled instrument has crowded scale because current is proportional to

Which of the following is an essential part of a motor meter ?

Aluminium when adopted as a conductor material in ______ transformers, decreases the overall cost of the transformer

Commonly used standard capacitor is

Damping of the Ballistic galvanometer is made small to

The high voltage winding is usually which of the following type ?

The change in flux linkages can be caused in which of the following ways ?

In a D.C. machine the number of brush arms is _____ the number of poles.

The operation of a D.C. machine with large air gap lengths is comparatively

Operating torques in analogue instruments are

The principle on which vector voltmeter is based is

Which of the following is the major consideration to evolve a good design ?

The stator of phase shifting transformer for use in conjunction with an A.C. potentiometer usually has a

Which of the following problem arises in D.C. motors which are fed from thyristor bridge circuits ?

The cylindrical windings using circular conductors are used for current rating of

The forced oil and air circulation method is usual one for transformers of capacities

In an energy meter braking torque is produced to

In a portable instrument, the controlling torque is provided by

In a meggar controlling torque is provided by

Systematic errors are

In a D.C. machine, the value of peripheral speed should not, normally, exceed

A moving-coil permanent-magnet instrument can be used as _____ by using a low resistance shunt.

Volt box is a component to

For measuring current at high frequency we should use

In an AC co-ordinate potentiometer, the currents in the phase and quadrature potentiometer are adjusted to be

The adjustment of position of shading bands, in an energy meter is done to provide

A multirangq instrument has

Which of the following are integrating instruments ?

The use of _____ instruments is merely confined within laboratories as standardizing instruments.

In a low power factor wattmeter the pressure coil is connected