Transformers, Electrical Engineering

AC Operation of an iron core

1428_Transformers.png

 

 

 

563_Transformers 1.png

 

Hence, if a wattmeter were used to measure the power delivered over a full period of the waveform (which will also be the average power delivered over a long period of time), the answer should be zero.  In practice, there will be a finite energy loss recorded, which is found to be much larger when the coil is wound on a conductive former than when it is air cored.

The energy loss is attributed to:
 
 
1) 'Copper losses', i.e. loss due to current flowing through the resistance of the windings, (P=iR).This power loss occurs whether the
core is air cored or not.

2) 'iron losses'. These arise due to two causes:
 
a)  the hysteresis loss due to the energy dissipated in continually reversing the magnetisation of the core. The energy taken per cycle is the area of the hysteresis B/H curve.

b) Eddy current losses due to  induced currents circulating within the conductive core of the coil. These are induced by the changing current in the coil and circulate in such a way as to try to oppose the change in the coil current. They are minimised by laminating the core to increase the path resistance for the circulating current and hence reduce its value. Since Power = i.R, reducing the current reduces the power even though the resistance is increased.

A transformer is produced by winding a second coil onto the former.

1393_transformer is produced by winding a second coil.png

 

Note the polarity of the currents. The current in the primary coil creates a flux in the core with a direction according to Maxwell's RH corkscrew rule. The current induced into the secondary coil is in such a direction as to try to oppose the original flux change in the core.

 

 

Posted Date: 8/23/2012 3:16:26 AM | Location : United States







Related Discussions:- Transformers, Assignment Help, Ask Question on Transformers, Get Answer, Expert's Help, Transformers Discussions

Write discussion on Transformers
Your posts are moderated
Related Questions

An induction motor takes 350 kW at 0.8 power factor lagging while driving a load. When an overexcited synchronous motor taking 150 kW is connected in parallel with the induction mo

a. Determine the circuit of three transistors dynamic RAM cell and define briefly read and write functions. b. Write short note on factors influencing choice of layer for wiring

Salient Features of NEP: Access to electricity: The policy not only envisages access to electricity for all but it also emphasizes in which all consumers, particularly t


Q. Frequency stability of quartz crystals ? The amount of frequency deviation from the ambient temperature frequency over the operating temperature range. This deviation is ass

Explain protected mode interrupt. In this mode, interrupts have exactly similar assignments as in real mode, but the interrupt vector table is not same. In place of interrupt

Q. What is positive clipper? Give 2 types of its applications ? In the series positive clipper, when the input voltage is positive, the diode does not conduct and acts an open

Draw the re-model for the circuit given in figure and calculate: a). The input impedance (β=100), b). The output impedance (r0 = 50 kΩ) and c). The mid-band collector-base

Write a computer program to implement the finite difference method. The program can be in any computer language that is available within the school. Set up the code to find the pot