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String efficiency is used for measuring the degree of utilization of SCR.
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Description : method for improving string efficiency 

Answer : The Methods of Improving String Efficiency:-   1) By reducing value of ‘m’ or (‘k’) by using longer cross arm. 2) By Making of ‘m’ or (‘k’) equal to zero 3) By grading Insulator. 4) By Using guard ring.

Description : Give the classification of the errors used in measuring instrument & state the reason for their occurrence.

Answer : Types of errors in measuring instruments:  A) Gross error: These are due to mistakes on the part of person using the instrument.  B) Systematic Error:  i) Instrumental Error: These ... multiplying factor.  C) Random error: These persist even after gross and systematic errors are removed. 

Description : The number of insulator discs (each rated 11 kV) required in a suspension type insulator string of 220 kV line is 

Answer : The number of insulator discs (each rated 11kV) required in a suspension type insulator string of 220 kV line is 16

Description : List out any four effects of electric current used in measuring instruments & write name of meter working on it.

Answer : Effects of Electric Current used in measuring instruments:  1. Magnetic Effect: PMMC and Moving Iron type Ammeters, voltmeter and Dynamometer type wattmeters etc.  2. Electromagnetic induction ... . Electrostatic effect: Voltmeters.  5. Hall Effect: Flux meter, Poynting vector wattmeter.

Description : When measuring insulation resistance of cables using d.c. source, the galvanometer used should be initially short circuited because  (A) Cables have a low value of capacitance which draws a high ... high value of charging current (D) Cables have a low value of capacitance and initial resistance

Answer : When measuring insulation resistance of cables using d.c. source, the galvanometer used should be initially short circuited because Cables have a high value of capacitance which draws a high value of charging current

Description : calibration and the need of calibration for measuring instruments.

Answer : Calibration - It is a process of estimating the value of a quantity by comparing that quantity with a standard quantity.    Need of calibration: - Calibration defines the accuracy and ... aim of calibration is to minimize any measurement uncertainty by ensuring the accuracy of test equipment.

Description : List three types of errors in measuring instruments. Give reasons of occurring for any one of them.

Answer : Types of errors in measuring instruments:  A) Gross error: These are due to mistakes on the part of person using the instrument.  B) Systematic Error: i) Instrumental Error: These ... multiplying factor.  C) Random error: These persist even after gross and systematic errors are removed.

Description : Describe spring control method of producing controlling torque in measuring instrument. Write any two properties required for spring material.

Answer : A)Spring control method: As shown in the figure, the inner ends of the both springs are attahced to the spindle, while outer end of upper spring is attached to the lever and outer ... of spring material: 1.Non Magnetic material 2.Low specific resistance 3.Low temperature coefficient of resistance

Answer : For measuring a very high resistance we should use Meggar.

Answer : For measuring current at high frequency we should use thermocouple instrument.

Description : Electrical Measuring Instruments

Answer : Electrical Measuring Instruments

Description : Explain the essential toques in analog type measuring instruments.

Answer : List of torques in analog instruments:  1. Deflecting torque  2. Controlling / Restraining torque.  3. Damping torque.  1. Deflecting torque: To create deflection proportional to ... the speed higher will be the damping torque bringing the pointer to the equilibrium position quickly. 

Description : State two purposes of calibration of measuring instruments.

Answer : Purposes of calibration of measuring instruments: - The purpose of calibration is to ensure that readings of an instrument are consistent with other instruments. It is also important in determining the ... will need to be calibrated periodically to make sure it can function properly and safely. 

Description : Define following terms related to measuring instruments: i) Sensitivity ii) Selectivity.

Answer : i) Sensitivity: It is the ratio of the change in output signal to the change in input signal of quantity being measured.  ii) Selectivity: It is the term to describe fulfillment of the requirements of measurement by an instrument to be suitable for use in a given situation. 

Description : Name the different torque and their function in measuring instrument.

Answer : List of torques in analog instruments:  1. Deflecting torque  2. Controlling / restraining torque.  3. Damping torque.  1. Deflecting torque:  - To create deflection of pointer ... .  - Bring the pointer to standstill quickly.  - To minimize oscillations about final position. 

Description : What arc the errors occurring in measuring devices due to stray magnetic field and temp '? Explain how to compensate them.

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Description : Explain magnetic effect employed in measuring instrument.

Answer : Magnetic Effect:  I) In PMMC meters:  ➢ When a current is passed through a conductor, magnetic field is produced round the conductor. Due to this field when current ... field it experiences a mechanical force.  Examples: Electrodynamometer type instruments, Induction type instrument. 

Description : Describe systematic errors in measuring instruments. 

Answer : Systematic errors: -  ➢ Instrumental Error: These errors are caused due to the mechanical structure of measuring instrument.  a) Inherent shortcomings of instruments: Instrument may read ... or electrostatic fields.  ➢ Observational Error: Parallax errors, incorrect multiplying factor. 

Description : State the function of controlling torque in electrical measuring instrument.

Answer : Function of controlling torque  1. The function is to opposes the deflection force and increases with the increase in the deflection of the moving system, to limit its movement. 2. and brought ... set a position where the two opposing forces i.e. deflection and controlling forces are equal. 

Description : Define: (i) Resolution, (ii) Calibration, with reference to electrical measuring systems.

Answer : Resolution The smallest increment in input (the quantity being measured) which can be detected with certainty by an instrument is called its resolution or discrimination.  OR It is ... the measuring instrument with standard instrument to find out the error in the instrument under test.

Description : Why energy meter is integrating type measuring instrument?

Answer : Energy Meter is Integrating Type Measuring Instrument: Energy meter is used for measurement of energy, which is obtained by integration (summation) of power supplied over the particular time duration, hence it the integrating type measuring instrument. 

Description : List any four effects employed in measuring instruments.

Answer : Effects Employed in Measuring Instruments: 1. Magnetic Effect 2. Electromagnetic induction 3. Heating effect 4. Electrostatic effect 5. Hall Effect 

Answer : The desirable static characteristics of a measuring system are accuracy, sensitivity and reproducibility.

Description : For high efficiency of transfer of power, internal resistance of the source should be?

Answer : For high efficiency of transfer of power, internal resistance of the source should be less than the load resistance.

Answer : D.C. generators are normally designed for maximum efficiency around full-load.

Answer : The condition for maximum efficiency for a D.C. generator is variable losses equal to constant losses.

Answer : The range of efficiency for shaded pole motors is 5% to 35%.

Answer : Generators for peak load plants are usually designed for maximum efficiency at 50 to 75 percent full load.

Description : For a transformer, operating at constant load current, maximum efficiency will occur at?

Answer : For a transformer, operating at constant load current, maximum efficiency will occur at unity power factor.

Description : SEER: Seasonal Energy Efficiency Ratio (SEER)

Answer : SEER: Seasonal Energy Efficiency Ratio (SEER), is most commonly used to measure the efficiency of a central air conditioner. The higher the SEER, the more efficient the system OR It is the ... the ratio of total capacity to the total KW energy usage at specific humidity and temperature condition.

Description : State why a transformer always have an efficiency of more than 90%.

Answer : As transformer is static device with no moving parts, the losses due to friction & windage are completely absent. Hence transformer has efficiency of more than 90%.

Description :  Compare the salient features of LED and CFL based on: i] Lamp Efficiency ii] Life span 

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Description : Define PIV, TUF, ripple factor, efficiency of rectifier.

Answer : PIV: Peak Inverse Voltage (PIV) is defined as the maximum negative voltage which appears across non-conducting reverse biased diode. TUF : Transformer Utilization Factor (TUF) is defined as the ratio of DC output ... Efficiency of rectifier: η = DC output power/ AC input power = PLdc / Pac

Description : "Efficiency of thermal power station is low". — Justify. 

Answer : Justification: Efficiency of thermal power station is low":- Overall efficiency of T.P.P depends upon efficiency of boiler, turbine and alternator. The heat produced due to combustion of coal ... losses in thermal power plant is 71%, So efficiency of thermal power plant is less about 29% 

Description : Transformer efficiency

Answer : Transformer efficiency

Description : What is the efficiency of Class-B amplifier?  A) 68.50% B) 78.50% C) 88.50% D) 98.50%

Answer : What is the efficiency of Class-B amplifier?  A) 68.50% B) 78.50% C) 88.50% D) 98.50%

Description : The overall efficiency of Thermal Power Plant is equal to _______________ .  (A) Regenerative Cycle Efficiency (B) Renkine Cycle Efficiency (C) Carnot cycle efficiency (D) None of the above

Answer : The overall efficiency of Thermal Power Plant is equal to Regenerative Cycle Efficiency. 

Description : A transformer operates 24 hours day at full -load. It's full -load efficiency is :  (A) equal all day efficiency (B) more than all -day efficiency (C) less than all -day efficiency (D) equal to maximum efficiency

Answer : A transformer operates 24 hours day at full -load. It's full -load efficiency is : equal all day efficiency 

Description : The rankine cycle efficiency of steam power plant is  (1) 60-80% (3) 30-45% (2) 45-80% (4) 20-30%

Answer : The rankine cycle efficiency of steam power plant is 30-45%

Description : Transmission efficiency of a transmission line increases with the

Answer : Transmission efficiency of a transmission line increases with the increase in power factor and voltage

Answer : The efficiency of diesel locomotives is nearly 20 to 25 percent.

Answer : The overall efficiency of steam locomotive is around 5 to 10 percent.

Answer : The efficiency of a properly designed synchronous motor will usually fall in range 85 to 95%.

Answer : The efficiency of a power transformer is of the order of 98 percent.

Answer : An ideal transformer will have maximum efficiency at a load such that copper loss equal to iron loss.

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

Answer : The efficiency of two identical transformers under load conditions can be determined by back-to-back test.

Description : The efficiency of a transformer, under heavy loads, is comparatively low because?

Answer : The efficiency of a transformer, under heavy loads, is comparatively low because copper loss becomes high in proportion to the output.

Description : Which motor have more efficiency, synchronous motor or induction motor?

Answer : Synchronous motor has more efficiency.

Answer : The efficiency of transformer is Greater than electrical Machine because there is no rotational losses in transformer and there is no air gap losses in transformer so losses is less in transformer compare to electrical machine so efficiency is higher in case of transformer.

Answer : Transformer efficiency is maximum when copper losses are equal to iron losses.

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