# what do not change in transformer?

what do not change in transformer?

## 1 Answer

Frequency and power are constant in transformers. Suppose we apply 50 Hz input frequency then the output frequency will also be 50 Hz whether the transformer is step up or step down. Similar with power, power is the multiplication of voltage and current. In transformers, if the voltage is increase on secondary side the current is decreased on secondary side and hence power on primary side and secondary side remains constant.

## Related questions

Description : In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of?

Answer : In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of less than 15A.

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 resistor in which the resistance changes exponentially with change in temperature is called as A) Potentiometer B) Phototransistor C) Varactor D) Thermistor

Answer :  A resistor in which the resistance changes exponentially with change in temperature is called as Thermistor

Description : If we change the excitation of synchronous machine will it affect on power factor?

Answer : Yes, If we change the excitation of synchronous machine it will affect on power factor. If the synchronous motor is overexcited then it will have leading power factor and if the motor is underexcited then it will have lagging power factor.

Description : If we change the excitation of synchronous machine will it affect on motor speed?

Answer : No, If we change the excitation of synchronous machine it will not affect on motor speed.

Description : How does AC current change direction?

Answer : This  is  because  the  angle  at  which  the   magnetic  fields  cuts  across  a  winding  changes  its  poles  thus  current  has  to  change  dirention  .

Answer : Capacitor use in fan is made up of dielectic material which is in semi solid material having high capacity.but generation of heat in capacitor the semi solid material converted into dry solid because of ... capacity becomes lower and lower so for good result of our fan we have to change it.

Answer : Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds 150°C.

Description : What is the use of transformer?

Answer : The use of transformer  is to do lower or raise  the voltage or currents in an electrical  circuit.  That's quite so simple.

Answer : No-load current in a transformer lags behind the voltage by about 75°.

Answer : The purpose of providing an iron core in a transformer is to decrease the reluctance of the magnetic path.

Answer : In the transformer low voltage winding has got more cross-sectional area.

Answer : High voltage winding in a transformer has more number of turns.

Answer : The no load current in a transformer lags behind the applied voltage by an angle of about 75°.

Answer : In a transformer, routine efficiency depends upon load current and power factor of load.

Answer : Transformer breaths in when load on it decreases.

Answer : The purpose of providing iron core in a step-up transformer is to decrease the magnitude of magnetizing current.

Answer : In a transformer, the tappings are generally provided on low voltage side.

Answer : The use of higher flux density in the transformer design reduces weight per kVA.

Answer : The chemical used in breather for transformer should have the quality of cleansing the transformer oil.

Answer : The transformer ratings are usually expressed in terms of kVA.

Answer : The thickness of laminations used in a transformer is usually 0.4 mm to 0.5 mm.

Answer : conservator or a reservoir tank for insulating oil in transformer which used for balanced the onload oil level with help of oil level indicator which mount on middle part of reservoir tank.

Answer : The main reason for generation of harmonics in a transformer could be saturation of core.

Answer : The leakage flux in a transformer depends upon load current.

Answer : Noise level test in a transformer is a type test.

Answer : The core used in high frequency transformer is usually air core .

Answer : The value of flux involved in the e.m.f. equation of a transformer is maximum value.

Description : In an actual transformer the iron loss remains practically constant from no load to full load because?

Answer : In an actual transformer the iron loss remains practically constant from no load to full load because core flux remains practically constant.

Answer :  Sandwich type winding is used in 3 phase shell-type transformer.

Answer : The function of breather in a transformer is to arrest flow of moisture when outside air enters the transformer.

Description : Reduction in core losses and increase in permeability are obtained with transformer employing?

Answer : Reduction in core losses and increase in permeability are obtained with transformer employing core built-up of laminations of cold rolled grain oriented steel.

Answer : In a power or distribution transformer about 10 percent end turns are heavily insulated to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns.

Description : In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are?

Answer : In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are hysteresis and eddy current losses.

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 : If a transformer is continuously operated the maximum temperature rise will occur in?

Answer : If a transformer is continuously operated the maximum temperature rise will occur in windings.

Description : The hum in a transformer is mainly attributed to?

Answer : The hum in a transformer is mainly attributed to magnetostriction.

Description : The path of magnetic flux in a transformer should have?

Answer : The path of magnetic flux in a transformer should have low reluctance.

Description : Explain the effect of Harmonics on the Transformer.

Answer : Effect of Harmonics on the Transformer:  1. Core loss: Harmonic voltage increases the hysteresis and eddy current losses in the lamination. The amount of the core loss depends on ... small core vibrations.  5. Saturation problem: Sometimes additional harmonic voltage causes core saturation.

Description : List two special feature of welding transformer.

Answer : Special features of welding transformer: i) It is a step down transformer that reduces the source voltage to a voltage desired according to the demands of the welding process. ii) Having large primary turns and less ... V ii) Secondary voltage - 40 to 60 V iii) Secondary current - 200 to 600 A

Description : State two applications of isolation transformer

Answer : Applications of isolation transformer: i) Isolates the load equipment from supply ground: ii) Reduction of voltage spikes iii) It acts as a decoupling device. iv) Protects loads from harmonic distortion.

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 : Equivalent circuit of transformer

Answer : Equivalent Circuit Diagram of Transformer Referred to Primary: V1 -Primary Input voltage I1 - Input Current I0- Exciting current/ No load current Im- Magnetizing component ... equivalent of secondary terminal voltage ZL- Load impedance ZL ′- Primary equivalent of load impedance

Description : Single phase transformer

Answer : Single phase Transformer Transformer

Description : Write about transformer on DC.

Answer : Transformer on DC : Transformer cannot work on DC. Transformer works on electromagnetic induction principle. Electromagnetic induction principle means when flux linking with coil changes and EMF induced in it ... winding insulation will burn. https://youtu.be/TVp_0fIfxqY

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

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

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.

Description : State any four characteristics of core type transformer.

Answer : Characteristics of core type transformer: i) It has one window. ii) It has one magnetic circuit. iii) Core surrounds the winding. iv) Average length of core is more. v) Area of cross ... Better cooling for winding. vii) Mechnical strength is comparatively less. viii) Repair and maintenance is easy.

Description : Explain construction and working of single phase Auto transformer.

Answer : Construction of single phase auto transformer: (i) It has only one winding wound on a laminated circular magnetic core. (ii) The core is made of silicon steel stampings. (iii) The two terminals of the ... help of handle. 5) The same transformer can be used as step-up or step down auto-transformer

Answer : A transformer cannot raise or lower the voltage of a D.C. supply because Faraday's laws of electromagnetic induction are not valid since the rate of change of flux is zero.

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