# why transformer rating is measured in KVA?

Transformer generally rated in KVA

Copper losses ( I²R)depends on Current which passing through transformer winding while Iron Losses or Core Losses or Insulation Losses depends on Voltage. That's why the Transformer Rating may be expressed in kVA,Not in kW.
The power of transformer is apparent power because it has no power factor and it is the product of voltage and current.

## Related questions

Description : Why Transformer rating is given in kVA?

Answer : 1) The output of transformer is limited by heating due to the losses. Two types of losses in the transformer (i) Iron loss, (ii) Copper loss. 2) Iron loss depends on the transformer voltage (V). ... by load power factor. - Hence the transformer output is expressed in VA or kVA and not in kW.

Description : The kVA rating of Three-phase transformer with Voltage = 200V and Current = 100A will be :  (A) 34.64 kVA (B) 75 kVA (C) 20 kVA (D) None of the above

Answer : The kVA rating of Three-phase transformer with Voltage = 200V and Current = 100A will be : 34.64 kVA

Description : Define kVA rating of transformer.

Answer : kVA rating of transformer is defined as the product of voltage (V) and current (I) on primary side of transformer or secondary side of transformer divided by 1000. On both side the VA rating remains ... Mathematically kVA rating is given by, kVA rating of transformer = V1I1/1000 =V2I2/1000

Description : The rating of transformer may be expressed in ____________.  (A) kVAR (B) kW (C) kVA (D) Horse power

Answer : The rating of transformer may be expressed in kVA .

Description : A 40 kVA transformer has a core loss of 400 W and a full load copper loss of 800 W. The proportion of full load at maximum efficiency is

Answer : A 40 kVA transformer has a core loss of 400 W and a full load copper loss of 800 W. The proportion of full load at maximum efficiency is 0.707

Description : A 4000 kVA, 11 kV/132 kV delta-star connected 3-phase transformer has reactance, x1 = 0.12 p.u. The actual value of x1 referred to the low voltage side is (A) 0.85 Ω (B) 3.63 Ω (C) 36.3 Ω (D) 252 Ω

Answer : A 4000 kVA, 11 kV/132 kV delta-star connected 3-phase transformer has reactance, x1 = 0.12 p.u. The actual value of x1 referred to the low voltage side is 3.63 Ω

Description :

Answer : Iron loss of a transformer can be measured by low power factor wattmeter.

Description : What should be kVA rating of each transformer in V-V bank when three phase balanced load is 40 kVA ? (A) 19 (B) 28 (C) 37 (D) 23

Answer : What should be kVA rating of each transformer in V-V bank when three phase balanced load is 40 kVA ? (A) 19 (B) 28 (C) 37 (D) 23

Description : Why does the core of a transformer need to be laminated?

Answer : Transformer cores are laminated to reduce eddy current loss.

Description : Why does a transformer only work with an AC supply?

Answer : The transformer work depends on the induction as main principle ,for that AC is the right means

Description : why transformer don't work on DC supply?

Answer : A  DC  current  does  not  produce  a  changing  magnetic   field   which  is   capable  of  inducing   current   on   the   secondary    windings   of   a   transformer   through  mutual   induction   process.

Description :

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.

Description :

Answer : Transformer core is laminated to reduce Eddy current losses.

Description : The kVA rating required for a transformer that must handle a maximum load current of 8 A with a secondary voltage of 2 kV will be: A. 4 kVA B. 0.25 kVA C. 16 kVA D. 8 kVA

Answer : The kVA rating required for a transformer that must handle a maximum load current of 8 A with a secondary voltage of 2 kV will be: 16 kVA

Description : When two transformer of different kVA rating are connected in parallel they share the load in proportion to their respective kVA rating only when their:

Answer : When two transformer of different kVA rating are connected in parallel they share the load in proportion to their respective kVA rating only when their: P u impedance are equal

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 : Even at no-load, a transformer draws current from the mains. Why?

Description :

Why circuit breaker connect b)w two transformer  (same rating

Answer : Because two transformers connection is in parallel to share the load if any transformer is receives the surge current because of the fault so to protect the other transformer from the fault.

Description : What is the back E.M.F in Transformer ?

Answer : Back emf in transformer is when apply voltage in primary side of transformer. This voltage produce flux according to Faraday law electro magnetic induction. This flux called mutual flux and this ... secondary flux oppos the applied voltage according to lenz law. its called back emf of transformer

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 : Which of the following does not change in a transformer?  (A) Current (B) Voltage (C) Frequency (D) All of the above

Answer : Which of the following does not change in a transformer?  (A) Current (B) Voltage (C) Frequency (D) All of the above

Description : A certain transformer has 200 turns in the primary winding, 50 turns in the secondary winding and 120 volts applied to the primary. What is the voltage across the secondary?  (A) 30 Volts (B) 480 Volts (C) 120 Volts (D) 60 Volts

Answer : A certain transformer has 200 turns in the primary winding, 50 turns in the secondary winding and 120 volts applied to the primary. What is the voltage across the secondary?  (A) 30 Volts (B) 480 Volts (C) 120 Volts (D) 60 Volts

Description : The main purpose of using core in a transformer is to (A) decrease iron losses (B) eliminate magnetic hysteresis (C) reduce reluctance of the common magnetic circuit (D) prevent eddy current loss

Answer : Reduce Relucatnce of the common magnetic circuit.

Description :

How eddy current is produced in a transformer?

Description :

Answer : Transformer noise is generated due to vibration of core and winding this is because of magnetostriction and magnetomotive force.

Description :

Answer : Low voltage side is short circuited.

Description :

Answer : Primary is high voltage side and Secondary is low Voltage side.

Description :

Answer : High Voltage side is open circuited.

Description :

Answer : Primary side is low voltage side and secondary side is high voltage side.

Description :

Answer : In short circuit test of transformer the low voltage side is short circuited . On high voltage side the voltmeter is connected in parallel and ammeter in series and also a wattmeter is ... circuit test is done for determining impedance and losses. In this test iron losses is neglected.

Description : Explain the procedure to perform Short Circuit test on single phase transformer with circuit diagram.

Description :  transformer coupled amplifier

Description :

Description : Transformer efficiency

Description : Explain construction and working of isolation transformer.

Description : Write selection criteria of distribution transformer with any four points.

Answer : Selection Criteria for Distribution Transformer:  i) Ratings - The kVA ratings should comply with IS:2026 ( Part l )-1977*. The noload secondary voltage should be 433 volts for transformers to be ... is not necessary. vi) Cooling - The transformers covered in this group are generally ONAN, AN

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 : Compare RC coupled, transformer coupled and direct coupled amplifier based on four points.

Answer : Parameter RC coupled Transformer coupled Direct coupled  Coupling element Resistor and capacitor Transformer No element Impedance matching Poor Excellent good Frequency ... Low frequency amplifier,opamp Size and cost small Large and bulky least

Description : Introduction to transformer

Answer : .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed ... power start transformer, autotransformer, multiphase transformer, magnetic flux linkage transformer, resonant transformer etc.

Description : MATLAB design code and model description.

Description : Cylindrical type transformer has:  (A) Single magnetic circuit (B) Double magnetic circuit (C) All of the above (D) None of the above

Answer : Cylindrical type transformer has: Single magnetic circuit

Description : The transformer works on the principle of: (A) Mutual induction (B) Mutual capacitance (C) All of the above (D) None of the above

Answer : The transformer works on the principle of:  Mutual induction

Description : Which of the following 3-phase connection of a transformer causes interference with the neighbouring communication lines:  (A) Delta-Star (B) Star-Delta (C) Delta-Delta (D) Star-Star

Answer : Which of the following 3-phase connection of a transformer causes interference with the neighbouring communication lines: Star-Star

Description : A Step Up transformer :  (A) Steps up the level of Voltage (B) Steps down the level of current (C) Step up the level of Frequency (D) (a) and (b) only

Answer : A Step Up transformer : (A) Steps up the level of Voltage (B) Steps down the level of current (C) Step up the level of Frequency (D) (a) and (b) only

Description : Increasing the number of turns of wire on the secondary of a transformer will  (A) Decrease the secondary current (B) Increase the primary current (C) Have no effect on the secondary current (D) Increase the secondary current

Answer : Increasing the number of turns of wire on the secondary of a transformer will Decrease the secondary current

Description : Step-down transformer converts high voltage and low current into:  (A) How voltage and high current (B) High voltage and low current (C) Low voltage and high current (D) None of the above

Answer : Step-down transformer converts high voltage and low current into: Low voltage and high current

Description : Transformer has __________________ .  (A) Primary winding and secondary winding (B) Primary winding and Auxiliary winding (C) Auxiliary winding and secondary winding (D) None of the above

Answer : Transformer has Primary winding and secondary winding.

Description : What will happen if the primary of a transformer is connected to D.C. supply?  (A) Transformer will operate with low efficiency (B) Transformer will operate with high efficiency (C) No effect (D) Transformer may start to smoke and burn

Answer : What will happen if the primary of a transformer is connected to D.C. supply?  (A) Transformer will operate with low efficiency (B) Transformer will operate with high efficiency (C) No effect (D) Transformer may start to smoke and burn

Description : What would happen if a power transformer designed for operation on 50 Hz (frequency) were connected to a 500 Hz (frequency) source of the same voltage:  (A) Eddy Current and Hysteresis losses will be excessive  (B) Current will be too much high  (C) Transformer may start to smoke and burn  (D) No effect

Answer : What would happen if a power transformer designed for operation on 50 Hz (frequency) were connected to a 500 Hz (frequency) source of the same voltage:  (A) Eddy Current and Hysteresis losses will be ... will be too much high  (C) Transformer may start to smoke and burn  (D) No effect

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