What is the inrush current peak of the transformer?

What is the inrush current peak of the transformer? 
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1 Answer

Answer :

6 to 8 time that of full load current.  
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What is inrush current?

Description : What is inrush current?

Last Answer : the initial value of flux is zero when the transformer is energized. The, the flux reaches a peak value in half a cycle. Since power transformers operate near the knee of the saturation curve, a flux ... the order of 8 to 30 times the full-load current. This current is known as inrush current.

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When voltage and current developed in an AC circuit reach their peak values at the same time, the power factor is _____________. A. lagging B. leading C. maximum D. minimum

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A switchboard for an AC electrical system requires the use of which of the following devices? A. Frequency meter. B. Ohmmeter. C. Induction voltage regulator. D. Current transformer governor.

Description : A switchboard for an AC electrical system requires the use of which of the following devices? A. Frequency meter. B. Ohmmeter. C. Induction voltage regulator. D. Current transformer governor.

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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

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What is the maximum allowable primary current of a 2 KVA step-down transformer with a four to one turns ratio if connected across a 440 volt line? A. 1.1 amps B. 4.5 amps C. 18.1 amps D. 27.7 amps

Description : What is the maximum allowable primary current of a 2 KVA step-down transformer with a four to one turns ratio if connected across a 440 volt line? A. 1.1 amps B. 4.5 amps C. 18.1 amps D. 27.7 amps

Last Answer : Answer: B

Difference between Current Transformer (CT) and Potential Transformer (PT)

Description : Difference between Current Transformer (CT) and Potential Transformer (PT)

Last Answer : Current Transformers (CT) and Potential Transformers (PT) are used to measure the current and voltage in a circuit of the order of hundreds of amperes and volts respectively. A CT has large number of ... and flux density vary over a wide range whereas in PT, they vary over a limited range only

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.

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

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.

There Are A transformer And An Induction Machine. Those Two Have The Same Supply. For Which Device The Load Current Will Be Maximum? And Why?

Description : There Are A transformer And An Induction Machine. Those Two Have The Same Supply. For Which Device The Load Current Will Be Maximum? And Why?

Last Answer : The motor has max load current compare to that of trformer because the motor consumes real power.. and the trformer is only producing the working flux and its not consuming.. hence the load current in the trformer is because of core loss so it is minimum.

What is Eddy current loss in transformer?

Description : What is Eddy current loss in transformer?

Last Answer : In transformer, we supply alternating current in the primary, this alternating current produces alternating magnetizing flux in the core and as this flux links with secondary winding, there will be induced ... dissipated as heat. This type of energy loss is called eddy current loss of transformer.

How much is the no load current of transformer?

Description : How much is the no load current of transformer?

Last Answer : No load curent of transformer is 3 to 5% of rated current in transformer.

What are two components of no load current in transformer?

Description : What are two components of no load current in transformer?

Last Answer : i) IM (Magnetizing/reactive /wattless) current. It magnetizes core ii) Iw (Coreloss/ active/wattful ) current. It supplies hysteresis and eddy current loss and negligible I² R loss.

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

What are the functions of no-load current in a transformer ?

Description : What are the functions of no-load current in a transformer ?

Last Answer : No-load current produces flux and supplies iron loss and copper loss on no-load.

What are Current transformer?

Description : What are Current transformer?

Last Answer : They are protective devices used to measure very high value of current in power system. The Current Transformer ( C.T. ), is a type of instrument transformer that is designed to ... an alternating current in its secondary winding which is proportional to the current being measured in its primary

Explain why the no load current of an induction motor is much higher than that of an equivalent transformer.

Description : Explain why the no load current of an induction motor is much higher than that of an equivalent transformer.

Last Answer : In induction motor, due to the presence of the air gap, the magnetizing current that is required to set up the flux is much higher. The working component of the current has to meet the ... eddy current loss, friction and windage losses. Hence the no load current of induction motor is higher.

Why motor starting current is high compared to transformer charging current?

Description : Why motor starting current is high compared to transformer charging current? 

Last Answer : Transformer charging current is only 1% and that of motor starting current is 30 to 40%. Because of air gap between stator and rotor. If the air gap is more load taking capacity increases and if air gap is less the load taking capacity reduces.  

Why 6.6 kV transformer is resistance grounded by 10 ohms and current limited to 400 A?

Description : Why 6.6 kV transformer is resistance grounded by 10 ohms and current limited to 400 A?

Last Answer : a) To reduce burning and melting in faulted switchgear or machine. b) To reduce mechanical stresses in equipment. c) To reduce the electrical hazards by stray ground fault currents in the ground ... screen in 6.6 kV XLPE (cross-linked polyethylene). Therefore the cost of the cable decreases. 

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

For V/F control, when frequency is increased in transformer a) Core loss component current increases, Magnetizing component current decreases b) Core loss component current increases, Magnetizing component current increases c) Core loss component current decreases, Magnetizing component current decreases d) Core loss component current decreases, Magnetizing component current increases

Description : For V/F control, when frequency is increased in transformer a) Core loss component current increases, Magnetizing component current decreases b) Core loss component current increases, ... component current decreases d) Core loss component current decreases, Magnetizing component current increases

Last Answer : Ans: Core loss component current decreases, Magnetizing component current decreases

No load current in a transformer: (A) lags the applied voltage by 90° (B) lags the applied voltage by somewhat less than 90° (C) leads the applied voltage by 90° (D) leads the applied voltage by somewhat less than 90°

Description : No load current in a transformer: (A) lags the applied voltage by 90° (B) lags the applied voltage by somewhat less than 90° (C) leads the applied voltage by 90° (D) leads the applied voltage by somewhat less than 90°

Last Answer : Ans: B The primary input current under no load conditions has to supply (i) iron losses in the core i.e hysteresis loss and eddy current loss (ii) a very small amount of Cu loss in the primary (there being no Cu loss in secondary as it 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.

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)

Most AC voltmeters are calibrated to indicate __________. A. peak-to-peak voltage B. root-mean-square voltage C. average voltage D. peak voltage only

Description : Most AC voltmeters are calibrated to indicate __________. A. peak-to-peak voltage B. root-mean-square voltage C. average voltage D. peak voltage only

Last Answer : Answer: B

AC voltmeters are generally calibrated to read the ________. A. instantaneous voltage B. average voltage C. RMS voltage D. peak voltage

Description : AC voltmeters are generally calibrated to read the ________. A. instantaneous voltage B. average voltage C. RMS voltage D. peak voltage

Last Answer : Answer: C

Ammeters and voltmeters used in sinusoidal AC power systems indicate which of the following values of the waveforms measured? A. Peak value B. Root-mean-square value C. Average value D. Maximum value

Description : Ammeters and voltmeters used in sinusoidal AC power systems indicate which of the following values of the waveforms measured? A. Peak value B. Root-mean-square value C. Average value D. Maximum value

Last Answer : Answer: B

What is Resonant peak?

Description : What is Resonant peak?

Last Answer : Answer: Resonant peak is defined as the maximum value of the closed loop transfer function.A large resonant peak corresponds to large overshoot in the transient respose