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what is mean by rotating transformer ?

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Induction motor is a rotating transformer

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Description :

UNIT 1 fundamentals of AC rotating machine


Contents

1.1 Introduction

1.2 Advantages

1.3 Parts of AC machines

1.4 Synchronous speed

1.5 AC winding

1.6 Winding factor (Coil pitch and distributed winding)

1.7 Distribution factor

1.8 EMF equation of alternator or generator

1.9 Numericals

1.10 Harmonic

1.11 Slot harmonics

1.12 Harmonics minimization

Answer : 1.2 Advantages: In practices most of alternator have rotating magnetic field type construction with stationary armature due to following reason. The generation level of AC voltage may be in the range ... at high speed. Only two Slip rings are required to excited the field by AC supply.

Description : The slip of 400 V, three phase, 4 -pole induction motor when rotating at 1440 rpm is 

Answer : The slip of 400 V, three phase, 4 -pole induction motor when rotating at 1440 rpm is 4 percent

Description : State advantages of rotating field type alternators. 

Answer : Advantages of Rotating Field Type Alternator: 1) For high-voltage alternator, large space is required to accommodate conductors with insulation, as high voltage is induced in them. If field poles are placed ... is kept rotating. 8) Rotating field is comparatively light and can run with high speed. 

Description : For protection of rotating machines against lightning surges _______ is used.  (1) lightning arrester (2) capacitor (3) combination of lightning arrester and capacitor (4) lightning conductor and arrester

Answer : For protection of rotating machines against lightning surges combination of lightning arrester and capacitor is used. 

Description :

Answer : In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called armature.

Description :

Losses which occur in rotating electric machines and do not occur in transformers are?

Answer : Friction losses windage losses 

Description : What is an auto transformer starter?

Description :

Answer : The inverse definite mean time relays are used for over current and earth fault protection of transformer against internal short-circuits.

Description : The desirable properties of transformer core material are  (1) low permeability and low hysteresis loss. (2) high permeability and high hysteresis loss. (3) high permeability and low hysteresis loss. (4) low permeability and hysteresis loss.

Answer : The desirable properties of transformer core material are high permeability and low hysteresis loss.

Description : why induction motor is called rotating transformer?

Answer : Induction motor works on same principal as transformers work ie faradays law of electromagnetic induction. ie IM called as rotating transformer 

Description :

Explain energy conservation method in lighting system by using installation of separate transformer / servo stabilizer.

Answer : Energy conservation techniques by installation of separate transformer / servo stabilizer: The luminous efficiency of lamps depends upon the voltage applied across the terminals. It gives its best ... the voltage constant in that installation for giving best luminous efficiency of lamps.

Description :

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

Description :

The changes in the volume of transformer cooling oil due to the variation of atmospheric temperature during day and night is taken care of by which part of the transformer?

Answer : The changes in the volume of transformer cooling oil due to the variation of atmospheric temperature during day and night is taken care of by conservator.

Description :

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

Description :

Answer : The transformer laminations are insulated from each other by thin coat of varnish.

Description : The noise produced by a transformer is termed as?

Answer : The noise produced by a transformer is termed as hum.

Description : The maximum load that a power transformer can carry is limited by its?

Answer : The maximum load that a power transformer can carry is limited by its voltage ratio.

Description : Explain the single pass transformer design procedure step by step by giving its flowchart.

Answer : single pass transformer design procedure step by step by giving its flowchart:

Description : What is temperature rise in a transformer?

Answer : Temperature rise in a transformer is the temperature of the windings and insulation above the existing ambient or surrounding temperature.

Description : What is a transformer and how does it work?

Answer : A transformer is an electrical apparatus designed to convert alternating current from one voltage to another. It can be designed to step up or step down voltages and works on the magnetic ... or voltage ratio) between the primary and secondary depends on the turns ratio of the two coils.

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. 

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 : 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

Description : What is a capacitor voltage transformer? A) It is a transformer used in power systems to step up low voltage signals and provide extra high voltage B) It is a transformer used in power systems to step up high voltage signals and provide extra high voltage C) It is a transformer used in power systems to step down extra high voltage signals and provide low voltage D) None of these

Answer : What is a capacitor voltage transformer? A) It is a transformer used in power systems to step up low voltage signals and provide extra high voltage B) It is a transformer used in power systems ... power systems to step down extra high voltage signals and provide low voltage D) None of these

Description : To protect the power transformer (Y-Y with neutral grounded) against fault, what type of connection do the CTs have ?

Answer : To protect the power transformer (Y-Y with neutral grounded) against fault, what type of connection do the CTs have ? Δ-Δ connection

Description :

what do not change in transformer?

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 ... is decreased on secondary side and hence power on primary side and secondary side remains constant.

Description :

What is impulse voltage of transformer?

Description : What are the design constraints of transformer design?

Answer : Design constraints of transformer design: Core loss, flux density, copper loss and total power loss vs flux density these are the basic constraints in transformer design. Core loss: Flux density: Copper loss: Total power loss vs flux density:

Description : What is the EMF equation of the transformer?

Answer : E1 =2(3.142)fN1 (flux)1E2 =2(3.142)fN2(flux)2

Description : What is the use of Buchholz relay in transformer?

Answer : This is a transformer that is used to step up and down current. 

Description :

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

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 : Can a Single Phase Transformer be used on a Three Phase source?

Answer : Yes. Any single phase transformer can be used on a three phase source by connecting the primary leads to any two wires of a three phase system, regardless of whether the source is three phase 3-wire or three phase 4-wire. The transformer output will be single phase.

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 : Polarity Test of Transformer

Answer : .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

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

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

Description : Explain the open delta (delta-delta) test on transformer.

Description : Define Dielectric Strength for transformer oil. State its value for new transformer oil.

Description :  transformer coupled amplifier

Answer :  transformer coupled amplifier

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.

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