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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 the difference between working
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Commutation Process in Detail

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Commutation process

  • Just before the armature coil reaches the brush, it carries current (= Ia / A ) in one direction after coil has traversed brush width, current gets reversed to ( -Ia / A ). This reversal of current is called Commutation. Here, A represents number of parallel paths.
  • Good commutation means no sparking at brushes and commutator surface remains unaffected.
                       
(a)









(b)

(c)

(d)


(e)



  • So, current in coil reduces from Ic to zero and then increase in negative direction to Ic again.
  • Under commutation : Tcommutation > Tc
  • Over commutation : Tcommutation < Tc
  • Commutation period, Tc = Brush width / Commutator peripheral speed

Resistance Commutation :-


Rc = coil resistance
r1 = Resistance between bar1 and brush
r2 = Resistance between bar2 and brush

If no emf is induced in commutated coil, then applying KVL in brush bar1 and bar2

(2Ic - I2)r1 + (Ic - I2)Rc - I2.r2 = 0

I2 = (Rc + 2.r1)Ic / (Rc + r1 + r2)Ic

Current in coil 1

ic = Ic - I2 = Ic[(r1 - r2) / ( RC + r1 + r2 ) ] = Ic[1 - {2r1/(r1 + r2)}] / [1 + {Rc/(r1 + r2)}]

Neglecting, Rc/(r1 + r2)

ic =  Ic[1- {2.r / (r1 + r2)}]

r ∝ 1/A

ic =  Ic[1- {(2/A1) / (1/A1 + 1/A2)} ]

With rotation to right A1 decreases and A2 increases linearly. In fractional kW DC machines, resistance commutation provides good commutation.





Delayed commutation :-

  • During commutation period, an emf is induced in coil due to self-inductance of coil.
ec = Lc.dic/dt

According to Lenz's law, induced emf opposes the cause so it oppose change in "ic" and thus delays the commutation.











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