The magnetic circuit shown below has uniform cross-sectional area and air gap of 0.2 cm. The mean path length of the core is 40 cm. Assume that leakage and fringing fluxes are negligible. When the core relative permeability is assumed to be infinite, the magnetic flux density computed in the air gap is 1 tesla. With same Ampere-turns, if the core relative permeability is assumed to be 1000 (linear), the flux density in tesla (round off to three decimal places) calculated in the air gap is ____________.

A three-winding transformer is connected to an AC voltage source as shown in the figure. The number of turns are as follows: . If the magnetizing current is neglected, and the currents in two windings are  = and =  A, then what is the value of the current  in Ampere?

A single phase 10kVA, 50Hz transformer with 1kV primary winding draws 0.5A and 55W, at rated voltage and frequency, on no load. A second transformer has a core with all its linear dimensions  times the corresponding dimensions of the first transformer. The core material and lamination thickness are the same in both transformers. The primary windings of both the transformers have the same number of turns. If a rated voltage of 2kV at 50Hz is applied to the primary of the second transformer, then the no load current and power, respectively, are

The single phase, 50Hz, iron core transformer in the circuit has both the vertical arms of cross sectional area  and both the horizontal arms of cross sectional area . If the two windings shown were wound instead on opposite horizontal arms, the mutual inductances will

In transformers, which of the following statements is valid?

Figure shows an ideal three-winding transformer. The three windings 1, 2, 3 of the transformer are wound on the same core as shown. The turn’s ratio is 4:2:1. A resistor of 10Ω is connected across winding-2. A capacitor of reactance 2.5Ω is connected across winding-3. Widing-1 is connected across a 400 V, ac supply. If the supply voltage phasor = 400∠0°, the supply current phasor is given by

A 400V/200V/200V, 50 Hz three winding transformer is connected as shown in Figure. The reading of the voltmeter, V, will be

In a constant voltage transformer (CVT), the output voltage remains constant due to

Given figure shows a magnetic circuit formed by an ideal core material. Determine the magnetic flux density in the air gap.

The function of oil in a transformer is

Supply to one terminal of a delta-wye connected three-phase core type transformer which is on no-load, fails. Assuming magnetic circuit symmetry, voltages on the secondary side will be:

Two transformers of the same type, using the same grade of iron and conductor materials, are designed to work at the same flux and current densities; but the linear dimensions of one are two times those of the other in all respects. The ratio of kVA of the two transformers closely equals

The relative current directions through the Primary (P) and Secondary (S) of a single phase transformer connected to a resistive load on the secondary side, are indicated in the various cross-sectional views given in figure. Which of these are correct representations

A toroidal iron ring has a uniform cross-sectional area of 50, and a mean magnetic path length of 100mm. the ring has an air-gap of 1mm, the ring is excited with a dc current of 1 A through a coil of 100 turns wound uniformly along its length. The iron may be assumed to be perfect magnetic material. The effect of fringing at the gap may be assumed to increase the effective area of magnetic flux at the gap by 10%.

Evaluate
(a) The exciting mmf of the coil
(b) The effective reluctance of magnetic circuit
(c) The inductance of the coil
(d) The energy stored in the magnetic field under the above excitation.