Instrument transformers are?

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1 Answer

Answer :

Instrument transformers are potential transformers, current transformers.

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In a PMMC instrument, the damping provided is :

Description : In a PMMC instrument, the damping provided is :  (A) air damping (C) eddy current damping (B) fluid damping (D) magnetic damping using a magnet

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A PMMC instrument has FSD of 100 μA and a coil resistance of 1 kΩ. To convert the instrument into an

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Eddy current damping cannot be used for moving iron instrument because

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Last Answer : Eddy current damping cannot be used for moving iron instrument because the presence of a permanent magnet required for such purpose would affect the deflection and hence the reading of the instrument

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The rectifier instrument is not free from?

Last Answer : The rectifier instrument is not free from frequency error.

A multirange instrument has?

Last Answer : A multirange instrument has multiple shunt or series resistances inside the meter.

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

Last Answer : The gravity controlled instrument has crowded scale because current is proportional to sine of deflection angle.

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

Last Answer : If an instrument has cramped scale for larger values, then it follows logarithmic law.

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

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

Last Answer : The ratio of maximum displacement deviation to full scale deviation of the instrument is called linearity.

The scale of a rectifier instrument is?

Last Answer : The scale of a rectifier instrument is linear.

A moving iron instrument can be used for?

Last Answer : A moving iron instrument can be used for both D.C. and A.C.

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

Last Answer : The disc of an instrument using eddy current damping should be of conducting and non-magnetic material.

In a portable instrument, the controlling torque is provided by?

Last Answer : In a portable instrument, the controlling torque is provided by spring.

The pointer of an indicating instrument should be?

Last Answer : The pointer of an indicating instrument should be very light.

Which is an instrument which measures insulation resistance of an electric circuit relative to earth and one another?

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

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

Last Answer : A moving-coil permanent-magnet instrument can be used as ammeter by using a low resistance shunt.

74)Power transformers are generally designed to have maximum efficiency around A. No load B. Half load C. Near full load D. 10% overload

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[23] Transformers are rated in KVA instead of KW because A. load power factor is often not known B. KVA is fixed whereas KW depends on load power factor C. Total transformer loss depends on volt ampere D. It has become customary

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Last Answer : Ans. Following are the schedules of maintenance on transformers. a. Daily maintenance. b. Monthly maintenance. c. Quarterly maintenance. d. Half yearly maintenance. e. Yearly maintenance. f. 5 Yearly maintenance.

Why a transformer requires cooling. What are the methods of cooling transformers?

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Last Answer : Ans. Transformers requires cooling as they get heated up due to various losses taking place in the transformer. (like iron of copper losses) Following are the methods of cooling of transformer. a. Natural ... . Forced oil air Natural Cooling (OFAN). d. Forced oil and forced Air cooling (OFAF).

What are the loses in Transformers, Explain?

Description : What are the loses in Transformers, Explain?

Last Answer : Ans. (1) Iron loses (2) Copper loses Iron Loss : Iron loss occurs in the transformers Iron core due to hysteresis and eddy currents taking place. They are almost fixed irrespective of ... losses in the primary and the secondary windings of the transformer which with the loading of transformer.

Classify the transformers based on the construction, frequency and power.

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Which of the following connection of transformers will give highest value of secondary voltage ?

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Two transformers A and B having equal outputs and voltage ratios but unequal percentage

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Core type transformers are popular in___________.

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In a transmission line if booster transformers are to be used, preferred location will be

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The friction losses in Real Transformers are :

Description : The friction losses in Real Transformers are :  (A) 0% (B) 5% (C) 25% (D) 50%

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Two 3-phase transformers cannot be operated in parallel, if their :

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An additional condition for parallel operation of three-phase transformers over single-phase transformers is that

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Which of the following is the advantage of using CRGO steel in transformers?

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Natural oil cooling is used for transformers up to a rating of?

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If the percentage impedances of the two transformers working in parallel are different, then?

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Distribution transformers are generally designed for maximum efficiency around?

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Power transformers are generally designed to have maximum efficiency around?

Last Answer : Power transformers are generally designed to have maximum efficiency around near full-load.

Two transformers do not have equal percentage impedance. This is likely to result in?

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Short circuit test on transformers is conducted to determine?

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For the parallel operation of single phase transformers it is necessary that they should have?

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Natural air cooling is generally restricted for transformers up to?

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Losses which occur in rotating electric machines and do not occur in transformers are?

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The efficiency of two identical transformers under load conditions can be determined by?

Description : The efficiency of two identical transformers under load conditions can be determined by?

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The efficiencies of transformers compared with that of electric motors of the same power are?

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of what use are current and voltage transformers in protective systems

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Why do transformers make noise?

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What are the test and measuring instrument required in an Electrical depots?

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List two advantages of PMMC instrument.

Description : List two advantages of PMMC instrument.

Last Answer : 1. It has uniform scale. 2. Power consumption is low 3. It can be obtained in wide ranges. 4. High sensitivity & accuracy 5. It is unaffected by external magnetic field. 6. Additional damping device not required. 7. Hysteresis problem is not there.

need of calibration and explain the procedure to calibrate the instrument.

Description : need of calibration and explain the procedure to calibrate the instrument.

Last Answer : Need of calibration: Every measuring device degrades over time due to normal wear and tear. These changes can be caused by various reasons such as electric or mechanical shock or a hazardous manufacturing ... different magnitude are used to calculate the resistance based on ohm's law.