“Secondary of current transformer should not be open”. Justify.

“Secondary of current transformer should not be open”. Justify.
by

1 Answer

Answer :

Secondary of a CT should not be Open Circuited: If secondary of CT is open circuited ,then current through secondary becomes zero hence the ampere-turns produced by secondary which generally opposes primary ampere-turns becomes zero. As there is no counter m.m.f., unopposed primary m.m.f (ampere-turns) produce high flux in the core. This produces excessive core losses, heating the core beyond limits. Similarly heavy e.m.f‟s will be induced on the primary and secondary side. This may damage the insulation of the winding. This is danger from the opeartor point of view as well. So secondary of a CT should not be open circuited. 

by

Related questions

Does the transformer draw any current when its secondary is open?

Description : Does the transformer draw any current when its secondary is open?

Last Answer : Yes, no-load primary current.

What current flows in the transformer primary when its secondary is open?

Description : What current flows in the transformer primary when its secondary is open?

Last Answer : A. When the secondary is open, there is no current in the secondary of the transformer. The primary takes a small current I0) from the source called no-load current which has a magnetizing ... ) producing the magnetic flux and a working component (I0 cosθ0) supplying real power for iron losses.

Does the transformer draw any current when secondary is open ? Why ?

Description : Does the transformer draw any current when secondary is open ? Why ?

Last Answer : Yes,it (primary) will draw the current from the main supply in order to magnetize the core and to supply iron and copper losses on no load . There will not be any current in the secondary since secondary is open

A 220/440 V, 50 Hz, 5 KVA, single phase transformer operates on 220V, 40Hz supply with secondary winding open circuited. Then (A) Both eddy current and hysteresis losses decreases. (B) Both eddy current and hysteresis losses increases. (C) Eddy current loss remains the same but hysteresis loss increases. (D) Eddy current loss increases but hysteresis loss remains the same.

Description : A 220/440 V, 50 Hz, 5 KVA, single phase transformer operates on 220V, 40Hz supply with secondary winding open circuited. Then (A) Both eddy current and hysteresis losses decreases. (B) Both ... same but hysteresis loss increases. (D) Eddy current loss increases but hysteresis loss remains the same.

Last Answer : (A) Both eddy current and hysteresis losses decreases.

When secondary of a current transformer is open-circuited its iron core will be?

Description : When secondary of a current transformer is open-circuited its iron core will be?

Last Answer : When secondary of a current transformer is open-circuited its iron core will be hot because of heavy iron losses taking place in it due to high flux density.

Calculate the resistance of shunt required to make a milliammeter which gives maximum deflection for a current of 15 mA and which has a resistance of 5 Ω; read up to 10 Amp.

Description : Calculate the resistance of shunt required to make a milliammeter which gives maximum deflection for a current of 15 mA and which has a resistance of 5 Ω; read up to 10 Amp.

Last Answer : Answer :

What is the output current of a 480 Volt primary 208 volt secondary - 3 phase transformer?

Description : What is the output current of a 480 Volt primary 208 volt secondary - 3 phase transformer?

Last Answer : You need to mention the Load connected to find the current.

Which of the following statements identifies the difference between the primary windings and the secondary windings of a 2:1 stepdown transformer? A. The secondary windings have twice as much resistance as the primary windings. B. The secondary windings give off twice as much heat as the primary windings. C. The secondary windings require half as much current as the primary windings. D. The secondary windings have half as many turns as the primary windings.

Description : Which of the following statements identifies the difference between the primary windings and the secondary windings of a 2:1 stepdown transformer? A. The secondary windings have twice as much resistance ... primary windings. D. The secondary windings have half as many turns as the primary windings.

Last Answer : Answer: D

A load with an impedance of 440 ohms is connected across the secondary of the transformer illustrated. If the input voltage is 110 VAC and the step-up ratio is 10 to 1, what will be the primary current? EL-0055 A. 2.5 amps B. 25 amps C. 250 amps D. current cannot be determined with information given

Description : A load with an impedance of 440 ohms is connected across the secondary of the transformer illustrated. If the input voltage is 110 VAC and the step-up ratio is 10 to 1, what will be the primary current? EL-0055 A. 2.5 amps B. 25 amps C. 250 amps D. current cannot be determined with information given

Last Answer : Answer: B

A load is connected to the secondary of the transformer illustrated and the current through the load is 10 amps. If the step-up ratio is 10 to 1 and the input voltage is 110 VAC, what will be the current flow through the primary? EL-0055 A. 1 amp B. 10 amps C. 100 amps D. 1000 amps

Description : A load is connected to the secondary of the transformer illustrated and the current through the load is 10 amps. If the step-up ratio is 10 to 1 and the input voltage is 110 VAC, what will be the current flow through the primary? EL-0055 A. 1 amp B. 10 amps C. 100 amps D. 1000 amps

Last Answer : Answer: C

Which of the following statements is true concerning stepdown transformer operation? A. The inductance on the primary side is the same as the inductance on the secondary side. B. The voltage to the primary side is the same as the voltage from the secondary side. C. The current to the primary side is the same as the current from the secondary side. D. The voltage to the primary side is greater than the voltage from the secondary side.

Description : Which of the following statements is true concerning stepdown transformer operation? A. The inductance on the primary side is the same as the inductance on the secondary side. B. The voltage to the primary ... . D. The voltage to the primary side is greater than the voltage from the secondary side.

Last Answer : Answer: D

The hook-on AC volt-ammeter consists essentially of a split-core and a rectifiertype instrument connected to the secondary winding of a _____________. A. potential transformer B. control transformer C. current transformer D. reactance transformer

Description : The hook-on AC volt-ammeter consists essentially of a split-core and a rectifiertype instrument connected to the secondary winding of a _____________. A. potential transformer B. control transformer C. current transformer D. reactance transformer

Last Answer : Answer: C

Increasing the load to the secondary windings of a transformer will cause a/an ____________. A. decrease in the primary voltage B. increase in the primary voltage C. decrease in the primary current D. increase in the primary current

Description : Increasing the load to the secondary windings of a transformer will cause a/an ____________. A. decrease in the primary voltage B. increase in the primary voltage C. decrease in the primary current D. increase in the primary current

Last Answer : Answer: D

What is the maximum current allowed to be drawn from the secondary of a 2 KVA step-down transformer with a turns ratio of four to one if connected across a 440 volt line? A. 1.1 amps B. 4.5 amps C. 18.1 amps D. 22.7 amps

Description : What is the maximum current allowed to be drawn from the secondary of a 2 KVA step-down transformer with a turns ratio of four to one if connected across a 440 volt line? A. 1.1 amps B. 4.5 amps C. 18.1 amps D. 22.7 amps

Last Answer : Answer: C

If we give 2334 A, 540V on Primary side of 1.125 MVA step up transformer, then what will be the Secondary Current, If Secondary Voltage=11 KV?

Description : If we give 2334 A, 540V on Primary side of 1.125 MVA step up transformer, then what will be the Secondary Current, If Secondary Voltage=11 KV?

Last Answer : A. As we know the Voltage & current relation for transformer-V1/V2 = I2/I1 We Know, VI= 540 V; V2=11KV or 11000 V; I1= 2334 Amps. By putting these value on Relation540/11000= I2/2334 So,I2 = 114.5 Amps

In transformer, alternating current is induced inA. primary coilB. secondary coilC. iron coreD. resistor

Description : In transformer, alternating current is induced inA. primary coil B. secondary coil C. iron core D. resistor

Last Answer : primary coil

If we give 2334 A, 540V on Primary side of 1.125 MVA step up transformer, then what will be the Secondary Current, If Secondary Voltage=11 KV?

Description : If we give 2334 A, 540V on Primary side of 1.125 MVA step up transformer, then what will be the Secondary Current, If Secondary Voltage=11 KV?

Last Answer :  As we know the Voltage & current relation for transformer-V1/V2 = I2/I1 We Know, VI= 540 V; V2=11KV or 11000 V; I1= 2334 Amps. By putting these value on Relation540/11000= I2/2334 So,I2 = 114.5 Amps

29. In transformer terminology, the ratio 20:1 indicates that A. there are 20 turns on primary one turn on secondary B. secondary voltage is 1/20th of the primary C. primary current is 20 times greater than the secondary current D. for every 0 turns on primary, there is one turn on secondary

Description : 29.In transformer terminology, the ratio 20:1 indicates that A. there are 20 turns on primary one turn on secondary B. secondary voltage is 1/20th of the primary C. primary current is 20 times greater than the secondary current D. for every 0 turns on primary, there is one turn on secondary

Last Answer : A. there are 20 turns on primary one turn on secondary

During short circuit test iron losses are negligible because A. The current on secondary side is negligible B. The voltage on secondary side does not vary C. The voltage applied on primary side is low D. Full-load current is not supplied to the transformer

Description : During short circuit test iron losses are negligible because A. The current on secondary side is negligible B. The voltage on secondary side does not vary C. The voltage applied on primary side is low D. Full-load current is not supplied to the transformer

Last Answer : C) the voltage applied on primary side is low

A 1:5 step-up transformer has 120V across the primary and 600 ohms resistance across the secondary. Assuming 100% efficiency, the primary current equals (A) 0.2 Amp. (B) 5 Amps. (C) 10 Amps. (D) 20 Amps.

Description : A 1:5 step-up transformer has 120V across the primary and 600 ohms resistance across the secondary. Assuming 100% efficiency, the primary current equals (A) 0.2 Amp. (B) 5 Amps. (C) 10 Amps. (D) 20 Amps.

Last Answer : I1= V1 /R1 = 120/600 = 0.2 (η = 100%, losses are zero ∴V1 = VR = I1R1)

During short circuit test iron losses are negligible because A. The current on secondary side is negligible B. The voltage on secondary side does not vary C. The voltage applied on primary side is low D. Full-load current is not supplied to the transformer

Description : During short circuit test iron losses are negligible because A. The current on secondary side is negligible B. The voltage on secondary side does not vary C. The voltage applied on primary side is low D. Full-load current is not supplied to the transformer

Last Answer : C) the voltage applied on primary side is low

The doorbell on your house requires a 12 volt alternating current. A transformer having a primary winding of 1,600 turns is to be used to step down your house's 110-volt alternating current. How many turns are there on the secondary winding?

Description : The doorbell on your house requires a 12 volt alternating current. A transformer having a primary winding of 1,600 turns is to be used to step down your house's 110-volt alternating current. How many turns are there on the secondary winding?

Last Answer : ANSWER: 175 TURNS 

The secondary of a current transformer is always short-circuited under operating conditions because it?

Description : The secondary of a current transformer is always short-circuited under operating conditions because it?

Last Answer : The secondary of a current transformer is always short-circuited under operating conditions because it avoids core saturation and high voltage induction.

Secondary growth is absent in monocotyledonous plants. Justify.

Description : Secondary growth is absent in monocotyledonous plants. Justify.

Last Answer : Secondary growth is absent in monocotyledonous plants. Justify.

State and justify which of the following two transformers is better: Transformer A = 4% voltage regulation Transformer B = 6% voltage regulation

Description : State and justify which of the following two transformers is better:  Transformer A = 4% voltage regulation  Transformer B = 6% voltage regulation

Last Answer : Transformer A with 4% voltage regulation is better.  Justification: Voltage regulation refers to the percentage change in secondary voltage when load is changed from no-load to full-load with primary voltage ... 4% voltage regulation, which is less as compared to 6% of transformer B, it is better.

Explain with neat sketch the construction and working principle of megger.

Description : Explain with neat sketch the construction and working principle of megger.

Last Answer : Megger: Construction of Megger : Two coils: the current coil and pressure coil are mounted at an angle on the same spindle and form the part of the moving system. These coils are ... force produces a torque that is used to deflect the pointer of the device which gives some reading.

Describe the procedure for the measurement of earth resistance by using earth tester.

Description : Describe the procedure for the measurement of earth resistance by using earth tester.

Last Answer : Measurement of earth resistance by using earth tester:  It is connected to earth electrode E, whose resistance is to be measured, and the other spike P and R, as shown in the ... , the deflection of the pointer will indicate directly resistance in ohm of the earth electrode under test. 

Explain the calibration of single phase electronic energy meter using direct loading.

Description : Explain the calibration of single phase electronic energy meter using direct loading.

Last Answer : Calibration of Single-phase Electronic Energy Meter by Direct Loading Method: The following figure shows the arrangement of calibration for single phase electronic energy meter. A phase shifter is connected for ... are taken for different values of current at different power factors. 

Draw block diagram of function generator and state the function of each block.

Description : Draw block diagram of function generator and state the function of each block. 

Last Answer : Block Diagram of Function Generator: OR Working of Function Generator : This instrument can deliver sine, triangular & square waves with frequency range of 0.01 Hz to ... output voltage reaches a predetermined level on the negative slope of the integrator's output voltage. 

Explain the effect of power factor on wattmeter reading in two wattmeter method for power measurement.

Description : Explain the effect of power factor on wattmeter reading in two wattmeter method for power measurement.

Last Answer : Effect of P.F. on Reading of Wattmeter in Two Wattmeter Method:

Explain with neat sketch; the construction and working principle of Repulsion type moving iron instrument.

Description : Explain with neat sketch; the construction and working principle of Repulsion type moving iron instrument.

Last Answer : Repulsion Type Moving Iron Instrument: Construction: It consist of fixed cylinder hollow coil which carries operating current inside the coil there are two soft iron pieces. One of which is ... magnetized with same polarity a repulsive force act on them and moving iron piece gets deflected. 

Draw the block diagram of tri-vector meter. State the various measurements possible from tri-vector meter.

Description : Draw the block diagram of tri-vector meter. State the various measurements possible from tri-vector meter.

Last Answer : Various measurements possible from tri-vector meter are: Tri-vector meter is a measuring instrument which measures the kWh, kVArh, the kVAh of a power line. Tri-vector meter is an energy meter ... of supply such as voltage, current, power factor, active load, reactive load, apparent load etc.

Describe with suitable example; frequency measurement by Lissajous patterns on CRO.

Description : Describe with suitable example; frequency measurement by Lissajous patterns on CRO. 

Last Answer : * Initially the unknown frequency signal is connected to vertical deflection plates of CRO. * Now switch of the internal sweep generator of the horizontal deflecting system. * A standard source ... explain by following example: Assume horizontal input frequency is 10 kHz for following pattern

Describe with block diagram the working of digital frequency meter.

Description : Describe with block diagram the working of digital frequency meter.

Last Answer : Digital frequency meter: Amplifier: The signal whose frequency is to be measured is first amplified and supplied to the schmitt trigger. Schmitt Trigger: The schmitt trigger convert ... count displayed on counter  t = time interval between start and stop condition of the gate 

Describe with block diagram; the principle of operation of digital storage oscilloscope.

Description : Describe with block diagram; the principle of operation of digital storage oscilloscope.

Last Answer : The block diagram of DSO is shown above. Sampling rate may be as high as 1,00,000 samples per sencod. For such high sampling rates, a fast conversion ADC is requried. Flash ADC ... particular signal in the memory then overwritting should be stopped.This obtained by using Hold and Save button.

Draw a neat labeled block diagram of 3-phase Electronic Energy meter.

Description :  Draw a neat labeled block diagram of 3-phase Electronic Energy meter.

Last Answer : Labeled diagram of 3-phase electronic energy meter:

Describe with block diagram; the construction of single phase electronic energy meter.

Description : Describe with block diagram; the construction of single phase electronic energy meter. 

Last Answer : Construction of Single Phase Electronic Energy Meter: 1. CT reduces current to reasonable value for current scaling network. 2. Voltage & current scaling networks reduce proportionally the ... The ADC converts the square wave frequency analog output to display the energy in Watt-hour.

Explain the error occurred due to pressure coil inductance of electrodynamometer type wattmeter. How this error is compensated?

Description : Explain the error occurred due to pressure coil inductance of electrodynamometer type wattmeter. How this error is compensated?

Last Answer : For power measurement assume that the pressure coil of wattmeter is purely restitive. Hence current taken by pressure coil Ipc is in phase with voltage across the pressure coil Vpc  ... inductive reactance XL the pressure coil circuit is made purely resistive and the error is eliminated.

Draw the circuit diagram for:- i) Measurement of active power in 3-phase load circuit using two wattmeter. ii) Measurement of reactive power in 3-phase load circuit using one wattmeter.

Description : Draw the circuit diagram for:- i) Measurement of active power in 3-phase load circuit using two wattmeter. ii) Measurement of reactive power in 3-phase load circuit using one wattmeter.

Last Answer : (i) Measurement of active power in 3- phase load circuit using two- wattmeter: (ii) Measurement of reactive power in 3- phase load circuit using one wattmeter

Explain with neat sketch, the working of full wave rectifier voltmeter.

Description : Explain with neat sketch, the working of full wave rectifier voltmeter.

Last Answer : Full Wave Rectifier Type Voltmeter: Working of full wave rectifier type A. C. Voltmeter Referring to the circuit diagram, for rectification, a full wave bridge circuit (ABCD) is used. Input ... current passing through meter is given as, which causes full scale deflection of the meter.

A permanent magnet moving coil instrument gives full scale deflection of 25mA when a voltage of 75mV is applied across it. Calculate: (i) Resistance of shunt required for full scale deflection of 150 A. (ii) Series resistance for full scale deflection of 500 V.

Description : A permanent magnet moving coil instrument gives full scale deflection of 25mA when a voltage of 75mV is applied across it. Calculate: (i) Resistance of shunt required for full scale deflection of 150 A. (ii) Series resistance for full scale deflection of 500 V.

Last Answer : Answer :

State the purpose of calibration of measuring instruments. Explain the procedure of calibration of D.C. voltmeter by using D.C. potentiometer.

Description : State the purpose of calibration of measuring instruments. Explain the procedure of calibration of D.C. voltmeter by using D.C. potentiometer.

Last Answer : Purpose of calibration : Calibration is the process of evaluating and adjusting the precision and accuracy of measuring equipment. Proper calibration of an instrument allows people to have a safe ... calibration curve can be drawn by plotting the percentage error against the measured voltages. 

List the types of systematic errors and state the reasons due to which these errors occur.

Description : List the types of systematic errors and state the reasons due to which these errors occur.

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

Compare analog instrument to digital instrument on the basis of accuracy, resolution, power required and portability.

Description : Compare analog instrument to digital instrument on the basis of accuracy, resolution, power required and portability. 

Last Answer : Comparison between Analog instruments & Digital instruments: 

State the advantages of electronic energy meter.

Description : State the advantages of electronic energy meter. 

Last Answer : Advantages of Electronic Energy Meter: 1) Low cost. 2) High accuracy. 3) More flexibility. 4) High sensitivity 5) No frictional losses. 6) Less loading effect. 7) High frequency ... for external adjustment. 11) Low load, full load, power factor and creeping adjustments are not required.

List the errors occuring in single phase electronic energy meter.

Description : List the errors occuring in single phase electronic energy meter.

Last Answer : Errors in Single Phase Electronic Energy Meter: 1) Error due to wrong sensor opeartion. 2) Error due to temperature. 3) Error due to wrong CT opeartion. 4) Error due to wrong PT opeartion. 5 ... of scaling network. 6) Error due to wrong ADC opeartion. 7) Error due to wrong Display. 

A single phase wattmeter rated for 500 V; 5A is having full scale deflection of 1000 watt. What is multiplying factor of the wattmeter?

Description : A single phase wattmeter rated for 500 V; 5A is having full scale deflection of 1000 watt. What is multiplying factor of the wattmeter?

Last Answer : Answer :

State the purpose of four quadrant meter.

Description : State the purpose of four quadrant meter.

Last Answer : Purpose of four quadrant meter:  Four-quadrant meter is basically a bidirectional energy-meter with additional measurement facility. The purposes of four-quadrant meter are: 1) Measurement of energy/power ... and kVARh 3) Time-of-use metering: Bidirectional consumption and demand.

State the working principle of PMMC Analog instrument.

Description : State the working principle of PMMC Analog instrument.

Last Answer : Working Principal of PMMC Analog Instrument: When current carrying conductor is placed in a magnetic field, it experiences mechanical force. In PMMC instrument, when current flows through a coil ... coil rotates and pointer attached to the coil shows deflection proportional to the current magnitude.

Differentiate between analog and digital multimeter.

Description : Differentiate between analog and digital multimeter.

Last Answer : Analog multimeter Digital multimeter 1. Power supply is not required 1. Power supply is required 2. Less suffered from electric noise 2. Suffered from electric noise 3. It provides measurement ... 9. Bigger in size 9. Compact in size 10. Economical 10.Expensive