Electrical Machines · Fundamentals

Series and Parallel Magnetic Circuits

Dr. Mithun Mondal BITS Pilani, Hyderabad Campus Electrical Machines

Demonstrative Video

SECTION 01

Ampere-turns Calculations

\[\phi=\frac{\text { m.m.f. }}{\text { reluctance }}=\frac{N I}{l / a \mu_{0} \mu_{r}}\]
\[\text { AT required, } N I=\frac{\phi l}{a \mu_{0} \mu_{r}}=\frac{B}{\mu_{0} \mu_{r}} l=H l\]
In a magnetic circuit, flux produced,
SECTION 02

Series Magnetic Circuits

  • In series magnetic circuit without air-gap \(NI=\Phi\Re=Hl\)

    series
    Series

  • It is a series circuit so same flux (\(\Phi\)) flows through the two medium- iron and air

    series air
    Series Air

  • Total reluctance \(\Re = \Re_{iron} + \Re_{air}\)

Key Concepts
  • \[\begin{aligned} H_{i} & =\dfrac{B}{\mu_{0}\mu_{i}}\\ H_{g} & =\dfrac{B}{\mu_{0}}\\ \therefore\Phi & =\dfrac{NI}{\left(\Re_{i}+\Re_{g}\right)} \end{aligned}\]
    too will be different Since value of permeabilities are different for iron and air, the corresponding values of
SECTION 03

Series-Parallel magnetic circuit

series parallel
Series Parallel
series parallel 1
Series Parallel 1
Key Concepts
\[\begin{aligned} \Phi & =\Phi_{1}+\Phi_{2}\\ NI & =Hl+H_{1}l_{1}+H_{g}l_{g}=\Re\Phi+\left(\Re_{1}+\Re_{g}\right)\Phi_{1}\\ \left(\Re_{1}+\Re_{g}\right)\Phi_{1} & =\Re_{2}\Phi_{2}\\ H_{1}l_{1}+H_{g}l_{g} & =H_{2}l_{2}\\ NI & =Hl+H_{2}l_{2} \end{aligned}\]