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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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Testing of DC Machines / Swinburne's Method / Advantages of Swinburne's Method / Disadvantages of Swinburne's Method

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 Swinburne's Method

One of the easiest ways of measuring no-load losses of a machine is by Swinburne's method.
Since this is a no-load test, it cannot be performed on DC Series Motors. This method is applicable for Shunt or Flat-Compound DC generators and motors. 
In this test, the machine, whether it is a generator or a motor, is run as a motor with no-load at rated speed and excitation.

If machine under test is generator, then
the voltage across the armature = rated terminal voltage + the voltage drop in the armature circuit resistance at rated armature current.

If machine under test is motor, then
the voltage across the armature = rated terminal voltage - the voltage drop in the armature circuit resistance at rated armature current.
Swinburne's method for measuring no-load losses of a DC Motor



Iao = No-Load Armature Current
If = Field Current
Vt = Terminal Voltage

→ Power input to the machine = Vt ( Iao + If ) 
Power taken by the armature = Vt Iao

Power taken by the armature is equal to the no-load rotational loss Wo plus a small amount of armature circuit copper loss  (Iao^2)Ra.

→ therefore, no-load rotational loss,    Wo = Vt Iao - (Iao^2)Ra

Here, Ra  is the armature circuit resistance including the brush contact resistance.
The Ra is determined by measuring the voltage drop across the armature circuit while rated current is passed through it at standstill. Ratio of this voltage and the current gives the value of the Ra.

→ Shunt field copper loss = Vt If

→ Let, IL be the load current at which machine efficiency is to be determined.

If Machine is run as a generator,

Armature current , Ia = IL + If 
Generator output, Po = Vt IL
Armature circuit loss = (Ia^2) Ra
Shunt field copper loss = Vt If
Therefore, total losses = Wo + (Ia^2) Ra + Vt If
Generator input, Pi =  Vt IL + Wo + (Ia^2) Ra + Vt If

Hence, Generator efficiency  𝜂g = Po/Pi  = (Vt IL) /(Vt IL + Wo + (Ia^2) Ra + Vt If)

If Machine is run as a motor,

Armature current , Ia = IL - If
Motor input, Pi = Vt IL
Armature circuit loss = (Ia^2) Ra
Shunt field copper loss = Vt If
Therefore, total losses = Wo + (Ia^2) Ra + Vt If
Motor output, Po = Vt IL - Wo - (Ia^2) Ra - Vt If

Hence, Motor efficiency  ðœ‚m = Po/Pi  = (Vt IL - Wo - (Ia^2) Ra - Vt If) /(Vt IL)



Advantages of Swinburne's method

  1. Low Power requirement for testing, even for large machines, since only no-load losses are to be supplied from the mains during testing.
  2. Efficiency of the machine can be estimated at any desired load.

Disadvantages of Swinburne's Method

(1)  The efficiency estimated by this method is always more than the actual value that can be obtained at the given load:
  • Large increase in iron losses when the machine is actually loaded, owing to increase in flux density at the teeth due to armature reaction.
  • Flow of Eddy currents within the armature conductors increases the current density value in armature conductors, causing increase in copper losses under actual loading condition. 
  • Presence of stray load losses that may take place during actual loading conditions.
(2)  Actual performance of the machine under loaded condition cannot be checked with Swinburne's method since in this test the machine is run under no-load condition only. Certain Performance, such as commutation and temperature rise, can only be correctly checked once the machine is actually loaded.







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