previous post

RICH DAD POOR DAD BOOK REVIEW

-
  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
Post a Comment

Construction Details of DC Machine

-
Construction Details of DC Machines

DC Machine has two parts Stator and Rotor. The Field Winding if DC Machines is wound on the Stator and Armature Winding is wound on the Rotor. Different parts of Stator and Rotor have been explained below:

Yoke

  • It provides path for pole flux ⲫ and carries half of it ⲫ/2.
  • It provides Mechanical support to whole machine.
  • Cast iron is used for small DC machines and fabricated steel for large DC machines.
  • If DC machines is operated through power electronic converter then yoke is laminated else not.




Field Poles

  • It consists of pole core and pole shoe.
  • Pole core is made of cast steel but pole shoe is laminated and fixed to pole core appropriately.
  • At present both pole shoe and pole core is laminated.
Field Winding

  • The pole excited by a winding wound around pole core.
  • The winding is made from copper.
  • Number of terns and cross-section of field winding depend on type of DC machine.
 →  For DC shunt machine, large number of turns and small cross-section because field winding has entire terminal voltage across it so large number of turns and larger length of conductor which implies high resistance so field current is small.

 → For DC series machine, number of turns and large cross-section as the field winding carries armature current so which is high so larger cross-section area which implies low resistance so less voltage drop and hence less number of turns.

  → For DC compound machines, both winding are employed.

Inter poles

  • Fixed to yoke in between main poles of DC machine.
  • Tapered with sufficient cross sectional area and wider at bottom to avoid magnetic saturation.
  • Inter pole winding consists of a few turns of thick wire is connected in series to armature. So MMF ∝ Ia
Compensating winding

  • Placed in slots cut in poles of a DC machine.
  • Connected in series with armature.
  • Used in large DC machines only.

Brushes

  • Housed in box type brush holders attached to stator end cover or yoke.
  • A small spring keeps them pressed to commutator.
  • Made of carbon in small DC machines, electro graphite for all and copper graphite for low-voltage, high current dc machines.
Armature core

  • Serves purpose of having armature coil in slots and providing low reluctance path to magnetic flux ⲫ/2.
  • Made of 0.35 mm to 0.50 mm, thick lamination of Si-steel to keep down iron losses.
Armature winding

  • Made of copper.
  • Large number of insulated coils, each having one or more turns.
  • Connected in series or parallel depending on type of winding.
  • Two coil ends of each coil are then connected to commutator.
         

Comments

Post a Comment

If you have any doubts, please let me know

Popular posts from this blog

Ideal Transformer (1-phase) Operation Under Load

-
Image
 What is Ideal Transformer ? An ideal transformer is a transformer with the following assumptions: Permeability of transformer is infinite. Iron loss in the transformer core are zero. Resistance of transformer winding is zero. No magnetic leakage flux, so coefficient of coupling is  1 . Magnetization curve of transformer is linear. Operation of Ideal transformer under load Schematic diagram of an ideal, 1-phase transformer under load When a finite impedance load Z L   is connected across the secondary terminals of a 1-phase transformer as shown in above figure, the load current I 2   flows through the secondary winding and the load. load current I 2   is given by:- I 2  = V 2 / Z L How will MMFs Produce ? A voltage source V 1   is connected to the primary winding. Due to this voltage V 1  primary current I 1   flowing through N 1   number of turns in the primary winding produces an MMF  N 1 .I 1   which creates the flux Ⲫ in the core. This flux links with the secondary coil and induc
Read more

RICH DAD POOR DAD BOOK REVIEW

-
  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
Read more

Compensating Winding

-
Image
Compensating Winding The cross magnetizing armature reaction effect that causes concentration of flux under one pole tip is caused mainly by the conductors that lie under the pole are. When the machines are heavily loaded, the flux density at these tips become very high resulting in higher than normal induced voltage between concerned adjacent commutator segments. This may cause a spark over between adjacent commutator segments more so because these coils are physically close to the commutation zone where air temperature is high and favorable for spark over. This may lead to other segments also getting involved and resulting in fire over entire commutator segment. Also if load is rapidly fluctuating (e.g. rolling machine), L(di/dt) voltage of coils may became high enough to start a spark over between adjacent commutator segments. This phenomenon will start from the coil under the pole center and it would have maximum. This problem is more acute when load is decrea
Read more