A single-phase 50 Hz transformer has 80 turns on the primary winding and 400 turns on the secondary winding. The net cross-sectional area of the core is 200 cm2. If the primary winding is connected to a 230 V, 50 Hz supply, determine: (a) the e.m.f. induced in the secondary winding; (b) the maximum value of the flux density in the core.

A single pahse transformer has 700 primary and 2100 secondary turns. The primary is connected to 400 V, 50 a.c. supply. If the net cross core is 100 cm². Calculate the maximum flux density in the core and induced e.m.f. in the secondary winding.

The core of a transformer operating at 50 Hz has an eddy current loss of 100 W/m3 and the corelaminations have a thickness of 0.50 mm. The core is redesigned so as to operate with the same eddycurrent loss but at a different voltage and at a frequency of 250 Hz. Assuming that at the new voltage themaximum flux density is one-third of its original value and the resistivity of the core remains unaltered,determine the necessary new thickness of the laminations.  Clear and detailed solution.

E In a transformer, the core loss is found to be 52 W at 40 Hz and 90 W at 60 Hz measured at same peak flux density. Compute the hysteresis and eddy current losses at 50 Hz.

A transformer has primary and secondary turns of 1250 and 125 respectively. It has core cross-sectionof 36 cm2 and its rms flux density is to be limited to 1.4 T (to prevent core saturation). Whatmaximum 50 Hz voltage can be applied on the primary side and the corresponding open-circuitsecondary voltage?The core has a mean length of 150 cm and its relative permeability can be assumed to be 8000. Whatwould be the rms exciting current when the transformer’s primary winding is excited at a voltage ascalculated above? Also calculate the magnetizing susceptance as seen from primary and secondarysides.If the transformer were to be excited at 60 Hz, 1. What should be the maximum primary voltage for thecore flux density limit not to be exceeded? 2. What would be the magnetizing susceptance as seen oneach side in this case?

An iron core is most often used in an AC transformer to1.provide a better coupling between the primary and secondary coils2.any of the choices mentioned3.to increase the magnitude of mutual inductance4.to channel most of the magnetic flux from primary to the secondary

(a) Explain briefly what is fringing effect and leakage flux. (b) A ferromagnetic core is shown in Figure 1. The depth of the core is 10 cm. The other dimensions of the core are as shown in the figure. By assuming the magnetic leakage to be negligible and relative permeability of the core is 800. Calculate the total reluctance and find the value of the current that will produce a flux of 0.01 Wb. With this current, calculate the flux density at the top of the core 20 cm 40 cm 10 cm, 30 cm 500 turns 30 cm 30 cm Figure 1

In a transformer, the core loss is found to be 60 watts at 30 Hz and 90 watts at 40 Hz measured at the same maximum flux density. Compute the eddy current and hysteresis losses at 60 Hz in watts.

A 3000/200-V, 50-Hz, 1-phase transformer is built on a core having an effective cross-sectional area of 150 cm2 and has 80 turns in the low-voltage winding. Calculate (a) the value of the maximum flux density in the core (b) the number of turns in the high-voltage winding.

The primary of a certain transformer takes 1 A at a power factor of 0.4 when connected across a 230 V, 50 Hz supply and the secondary is on open circuit. The number of turns on the primary is twice that on the secondary. A load taking 50 A at a lagging power factor of 0.8 is now connected across the secondary. Sketch, and explain briefly, the phasor diagram for this condition, neglecting voltage drops in the transformer. What is now the value of the primary current?