AC MACHINES (TRANSFORMER)

54問 • 2年前

問題一覧

Which of the following given below is the eddy current loss not proportional to?

Square of the load current

A 4, 400 volt, 60 Hz transformer has a core loss of 840 Watts, of which ine third is eddy current lost. Determine the care loss of this transformer when it is connected to a 4,600 Volts, 60 Hz

907 watts

A 50 kVA, 5000/500 V, 50 Hz, 1 phase transformer has 1400 watts rated copper loss of 1400 watts and rated core loss of 1000 watts. Calculate the efficuency of the transformer, if the output drops to 80% of the rated value at 80 % power factor lagging.

94.39%

In a single phase transformer, the core losses is 60 W at 40 Hz and 95 W at 60 Hz both measured at the same maximum vslie of the fluxdensity. Find the core losses in W at the frequency of 50 msj

Materials used for constraction of transformer core is usually

silicon steel

One of the following is not a basic part of oil type power transformer

load tap charger

What is the purpose of welded tubes at the sides of a transformer?

cooling

A common method of cooling a ppwer ttansformer is

oil cooling

The power transformer is a constant

main flux device

Which of the following does not change in a transformer?

frequency

A transformer is used to change the value of

voltage

Which of the following is not a psrt if transformer?

exciter

Which winding in a transformer has more number of turns?

high voltages winding

The transformer ratings are usually expresses in terms of

kVA

A transformer oil musy be free from

moisture

A buchholz relay can be installed on

oil cooled transformer

A tap changer is used on a transformer for

adjustment in secondary voltages

A step up transformer increases

voltages

In the transformers

low tension winding is used near the core

One primary and one secondary terminal of two winding transformer are conencted to a ohm meter instrument. What will be the reading on this instrument?

infinity

The starting / in rush cirrent of the transfomer is generally _________ a times of its full load

While conducting short circuit test on a transformer the following side is short circuited

low voltage side

Short circuit test on transformer is conducted to determine

copper losses

Open circuit test on transformer is conducted to determine

core losses

A 10 kVA, 200/400 V single phase transformer is operating with secondary open circuited. What is the input current in amperes?

Which of the following refers to the power loss due to alternating magnetization and demagnetization of the core material?

Hysteresis loss

Why is the core losses are negligible during short circuit test conducted on transformer?

mutual flux is small

A two winding transformer has core losses and full load copper losses equal to W watts each. It is tested along with another similar transformer for back to back test. What is the totak power input will be in W

four

The essentiak condition for parallel operation of two single phase transformer is that they should have the same ___________

Polarity

Two transformer operating in parallel will share the load depending upon thier

per unit impedance

Which of the following transformer winding connection is MOST suitable for an unbalanced load?

Four wye

Scott connections are used to convert

3 phase supply to two phase supply

In a transformer the energy is conveyed from primary to secondary

by flux

The chemical used in breather for transformer should have the quality of

absorbing moisture

The following are protection device built in for sale operation of a power transformer, EXPECT

pothead

What is the part of the power transformers that contains oil and absorb the swell of the coil?

Conversator

What is the device or part of transformer used to cool oil naturally

Radiator

In a transformer, if the load increases the temperature

Increases

Tap charger of transformer is located where?

HV side

An auto transforemr having transformation ratio 0.8 supplies a load od 3 kW. The power transferred conductively from primary to secondary is ________ kW

2.4

What is the typical use an auto transformer?

Variable transformer

For parallel operation of two single phase transformer the essential condition is that they should have the same

polarity

How to connect two single phase transformer for three phase banking?

Open delta

What is the normal secondary current rating of current transformer?

5 A

Transformer connection to convert two phase to three phase

Scott connection

Awhich of the following is not a routine test on transformer?

radio interferenfe test

Delta delta power transformer is protected sis protected by current transformer having

star/star connections

The colour of fresh dielectric oil for a transformer is

pale yellow

When 240 V DC supply is given to an unloaded 220 V 50 Hz transformer

primary will carry heavy current and may possibly burn

The saving in copper achieved by converting two winding transformer into an auto transofrmer is determined by

Voltage transformation ratio

Dust should never be allowed to accumulate on the windings and core of a dry type transformer beacause it

reduces dissipation of heat

Which if the following parts of a transformer is likely to suffer maximum damage due to exccesive

winding insulation

Which of the following is common to insulator busshing potential transformer and transformer winding?

BIL rating

In three phase transformer connected star delta the nuetral ground connection of the system can be established by using ____________

Zigzag transformer

DC CIRCUITS POWERLINE

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DC CIRCUITS POWERLINE