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What is the definition of a primary instrument?

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Description : What is the definition of induction motor?

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Description : What is the definition of extra low voltage?

Answer : Extra-low voltage (ELV) is an electricity supply voltage in a range which carries a low risk of dangerous electrical shock.

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Description : What is the definition of an electrical system?

Description : What is the definition of wind energy?

Answer : Motion of atmosphere of earth is called wind and its kinetic energy is called wind energy

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

Description : Define: primary and secondary distribution system 

Answer : i) Primary Distribution:  It is a 3-phase, 3-wire transmission line connected in between receiving substation to Distribution substation. OR It is link between receiving substation & ... substation to consumer line. OR It is link between distribution transformer substation & consumer. 

Description : Write example of each type (i) Primary transducer (ii) Active transducer (iii) Electrical transducer (iv) Digital transducer

Answer : (i) Active transducer:-Thermocouple, piezoelectric, photovoltaic cell (ii) Primary transducer:- Bourdon tube, bellows, (iii) Electrical transducer.:- LVDT,RVDT, Hall effect, strain gauge, ... , optical pyrometer, radiation pyrometer (iv) Digital transducer:- Linear Encoder, digital taco generator

Description : Compare primary and secondary instruments.

Answer : Primary instruments  Secondary instruments  Gives magnitude of quantity in terms of physical constants of instrument  Gives reading directly of the quantity measured.  Need no calibration  ... .  e.g. magnetic meter, induction meter, hotwire meter and electrostatic meter 

Answer : The primary reason for low power factor is supply system is due to installation of induction motors.

Answer : Primary winding of a transformer could either be a low voltage or high voltage winding.

Description : In a transformer the resistance between its primary and secondary should be?

Answer : In a transformer the resistance between its primary and secondary should be infinity.

Description : Primary and Backup Protection

Answer : Primary and Backup Protection  B,D,G,I are the primary protection. A,C,H,J are the backup protection. About 90% of faults are clear by Primary Protection. So ... ordinated backup (primary is at various station  and backup is at control room with computer)

Description : A Pyrheliometer is an instrument to measure :  (A) temperature of solar photovoltaic cell  (B) intensity of direct solar radiation at normal incidence  (C) intensity of indirect solar radiation  (D) efficiency of a solar photovoltaic cell

Answer : A Pyrheliometer is an instrument to measure : intensity of direct solar radiation at normal incidence 

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

Answer : In a PMMC instrument, the damping provided is : eddy current damping 

Description : A PMMC instrument has FSD of 100 μA and a coil resistance of 1 kΩ. To convert the instrument into an ammeter with full scale deflection of 100 mA, the required shunt resistance is (A) 1 Ω (B) 1.001 Ω (C) 0.5 Ω (D) 10 Ω

Answer : A PMMC instrument has FSD of 100 μA and a coil resistance of 1 kΩ. To convert the instrument into an ammeter with full scale deflection of 100 mA, the required shunt resistance is 1.001 Ω

Description : Eddy current damping cannot be used for moving iron instrument because

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

Description : Identify the instrument that does not exist (A) Dynamo-meter type ammeter (B) Dynamo-meter type wattmeter (C) Moving-iron voltmeter (D) Moving-iron wattmeter

Answer : Identify the instrument that does not exist (A) Dynamo-meter type ammeter (B) Dynamo-meter type wattmeter (C) Moving-iron voltmeter (D) Moving-iron wattmeter

Answer : Instrument transformers are potential transformers, current transformers.

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

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

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

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

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

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

Answer : The scale of a rectifier instrument is linear.

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

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

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

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

Answer : Meggar is an instrument which measures the insulation resistance of an electric circuit relative to earth and one another.

Answer : A moving-coil permanent-magnet instrument can be used as flux-meter by eliminating the control springs.

Description : What modifications are necessary if ac is applied to a PMMC instrument?

Description : List two advantages of PMMC instrument.

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.

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

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.

Description : feature of PMMC instrument. 

Answer : Consumes less power Great accuracy. High torque to weight ratio

Description : Write any four advantages of instrument transformer.

Answer : Advantages of instrument transformer: 1. Extension of instrument range is possible. 2. Isolation of instruments from high voltage side. 3. Power loss is less as compared to shunts and multipliers. 4 ... measurement. 5. It is economical method of range extension. 6. Increases in safety of operator.

Description : State the meaning of secondary instrument. Classify secondary instruments.

Answer : Secondary instruments: - Gives reading directly of the quantity being measured. - Calibrated with respect to absolute instruments  Classification of Secondary instruments:  1. Depending on the ... on permissible error: i) Standard meters ii) Substandard meters iii) First grade instruments.

Description : State the function of former and control spring in PMMC instrument.

Answer : Function of Former: To support the coil and provide eddy current damping.  Function of Control Spring: To provide control torque or force and in some instruments springs can be used as current leads.

Description : ‘PMMC instrument is not suitable to measure AC quantity’. State the reason.

Answer : The direction of force exerted on moving coil depends on the direction of current flowing through moving coil. If the direction of magnetic field is kept constant, it produces unidirectional torque if the current is ... on the coil in one cycle to zero. Hence the meter cannot read A.C. quantities.

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

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 : 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 : Name the material used for :- (i) Moving coil (ii) Permanent magnet in PMMC instrument.

Answer : (i) Material used for Moving coil: Copper, Aluminum( some times)  (ii) Permanent magnets are made of special alloys such as :  Aluminum-Nickel-Cobalt (Alnicos)  Strontium-Iron  Neodymium-Iron-Boron  Samarium-Cobalt.

Description : State the meaning of absolute instrument and secondary instrument. 

Answer : Absolute instruments:   These instruments read the quantity under measurement indirectly i.e. in terms of deflection, degrees and meter constant. The actual value under measurement can be calculated ... of operation (b) Depending upon permissible percentage error. (c) Depending upon application.

Description : State the advantages of instrument transformer in using for extension of range of meters. 

Answer : Advantages of instrument transformer: 1. Extension of instrument range is possible. 2. Isolation of instruments from high voltage side. 3. Power loss is less as compared to shunts and multipliers. 4 ... measurement. 5. It is economical method of range extension. 6. Increases in safety of operator.

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. 

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