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RICH DAD POOR DAD BOOK REVIEW

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  RICH  DAD  POOR  DAD  BOOK REVIEW This is amazing book.   • Explodes the myth that you need to earn a high income to become rich • Challenges the belief that your house is an asset • Shows parents why they can't rely on the school system to teach their kids about money • Defines once and for all an asset and a liability • Teaches you what to teach your kids about money for their future financial success It's been nearly 25 years since Robert Kiyosaki’s  Rich Dad Poor Dad  first made waves in the Personal Finance arena. It has since become the #1 Personal Finance book of all time... translated into dozens of languages and sold around the world. Rich Dad Poor Dad  is Robert's story of growing up with two dads — his real father and the father of his best friend, his rich dad — and the ways in which both men shaped his thoughts about money and investing. The book explodes the myth that you need to earn a high income to be rich and explains...
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Real Transformer (1-phase) Operation Under No-Load

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 What is Real Transformer ?

Real transformer is a transformer with the following assumptions:
  • Both the primary and secondary windings have finite non-zero resistances.
  • Along with the mutual flux, there will be some amount of leakage flux in the core.
  • Both types of magnetic losses, Hysteresis loss and Eddy current loss, will be present in the core.

Operation of Real transformer under no-load


Real transformer (1-phase) operation under no-load


When an alternating voltage V1  is applied to the primary terminals, a current I1  flows through the primary winding as shown in the schematic diagram of above figure. This current produces the necessary MMF in the primary winding that creates an alternating flux in the core. This alternating flux generates a self-induced EMF e1  in the primary winding and mutually induced EMF e2  in the secondary winding.

Different fluxes and its function :-

The flux produced by the primary winding can actually be divided into two parts. A major part of the flux that passes entirely through the iron core thereby linking both the coils is called the mutual flux or the useful flux Ⲫ. A small part of flux, known as the leakage flux Ⲫl , does not pass through the entire iron core, rather completes its path through air or other nearby metal parts. These leakage flux lines are shown as Ⲫl1 , Ⲫl2 , etc. in above figure.
        Although the useful / mutual flux induces an EMF e1  in the primary winding, the leakage fluxes also induce similar self-induced EMFs of different magnitudes in the same primary winding. Let the total EMF generated by the leakage fluxes linking the primary winding is el1  . Note that both the mutual flux Ⲫ and the leakage flux Ⲫl  are created by the same current i1 in the primary winding. Thus, both Ⲫ and Ⲫl are in the same phase as i1 . The EMFs they induce in primary winding, i.e. e1  and el1  are also in the same phase and are having same instantaneous polarity as indicated in above figure.


KVL Equation in primary winding

If the primary winding resistance is r1  , then KVL equation in the primary winding loop can be written as :
V1 + e1  + el1 = i1 r1

We know,  e1 = –N1 . dⲪ/dt           

and            el1 = – (n1 .dⲪl1/dt  +  n2 .dⲪl1/dt  +  n3 .dⲪl3/dt  +  ............)    

Where  n1 , n2 , n3 , ....... are the number of turns of the primary winding being linked by the leakage flux lines Ⲫl1 , Ⲫl1 , Ⲫl3 , ......., etc.

el1  = – L1 . di1 /dt 

Where L1  is the total self-inductance of primary winding that arises due to the flux leakage, and also called 'leakage inductance' of the primary winding.

el1 = – jωL1i1


Thus, the KVL equation for the primary winding circuit can be written as:-
V1  +  e1  –  jωL1i1  =  i1 r1

V1  = – e1  + i1 ( jωL1 + r1 )

The primary winding of a real transformer can thus be represented equivalently by its resistance r1 and leakage reactance ωL1 .

What is No-Load Current (Io) ?

In a real transformer, if there is no secondary MMF, there is always a small primary current present that gives the necessary MMF to create the flux in the core. This primary current flowing during the transformer no-load condition is called the 'no-load current' Io .

This no-load current, however, is very small, around 4-5 % of the transformer full load current rating. 

This no-load current Io  serves two purposes:
  1. It provides the necessary MMF to create the flux in the core.
  2. It carries the necessary energy from the supply source to account for the core losses, i.e., Hysteresis and Eddy current losses that take place in the magnetic core
The component of no-load current (Io), which is used to create the flux, is called the magnetizing current (Im) and it is in the same phase as the flux Ⲫ it creates.

The second component of no-load current which supplies the losses in the core is termed as the core loss component of current (Ih+e). 
Since this is an active component of current that supplies active power losses in the core, it must be in the same phase as the voltage drop across the core (– e1).

KVL equation under no-load

Under no-load condition, the primary current is the no-load current, and thus I1 = Io . Thus, the input voltage expression under no-load is given by:-

V1  = – e1  + io.jωL1 + ior1 


Equivalent representation of primary winding

The Primary winding resistance r1  and primary winding leakage reactance ωL1 can be represented as shown in below figure:-

Equivalent representation of primary winding circuit of a real transformer under no-load



Phasor diagram of real transformer

Phasor diagram of real transformer operation at no-load is shown in below figure:-

Phasor diagram of real transformer operation under no-load




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