# What is the back EMF in Transformers?

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What is the back EMF in Transformers?

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Do AC induction motors have back EMF?

The back emf of synchronous motor depends on?

Which of the following is the advantage of using CRGO steel in transformers? A) High magnetic flux density B) Low permeability C) Both A and B D) None of these

What is the EMF equation of the transformer?

What is Phase sequence? Draw waveforms of 3 phase emf.

The friction losses in Real Transformers are :  (A) 0% (B) 5% (C) 25% (D) 50%

The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is  (1) 1000V (2) 100V (3) 600V (4) 10,000V

Two 3-phase transformers cannot be operated in parallel, if their :  (A) kVAs are different (B) phase sequences are different (C) % impedances are different (D) voltage ratios are different

The fractional-pitch used for eliminating 7th harmonic from the emf wave of an alternator is (A) 2/3 (B) 5/6 (C) 7/8 (D) 6/7

Which of the following connection of transformers will give highest value of secondary voltage ? (A) Delta primary delta secondary (B) Delta primary star secondary (C) Star primary star secondary (D) Star primary delta secondary

Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in?

Explain the term self induced EMF with a neat diagram.

List the two types of induced EMF.

Two transformers A and B having equal outputs and voltage ratios but unequal percentage impedances of 4 and 2 are operating in parallel. The transformer A will be overloaded by

Core type transformers are popular in___________.  (A) High voltage applications (B) Low voltage applications (C) All of the above (D) None of the above

In a transmission line if booster transformers are to be used, preferred location will be  (A) At the receiving end (B) At the sending end (C) At the intermediate point (D) Anywhere in the line

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

An additional condition for parallel operation of three-phase transformers over single-phase transformers is that

Compare statically induced emf with dynamically induced emf on any four points.

Define: 1) statically induced EMF 2) dynamically induced EMF Write the names of equipments in which these two types of EMF get induced

Classify the transformers based on the construction, frequency and power.

The efficiency of two identical transformers under load conditions can be determined by?

The efficiencies of transformers compared with that of electric motors of the same power are?

Why do transformers make noise?

If the back emf of a dc motor is doubled and its speed is also doubled, the torque developed in the machine will  (1) get doubled (2) become 4 times (3) get halved (4) remain unaltered