Magnetomotive Force (MMF):
MMF is the force that drives magnetic flux through a magnetic circuit.
Analogous to electromotive force (EMF) in electric circuits.
Formula:
\text{MMF} = N \cdot I
Unit: Ampere-turns (At).
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2. Magnetic Force:
Magnetic force arises between moving charges or magnets.
Formula for force on a current-carrying conductor in a magnetic field:
F = B \cdot I \cdot l \cdot \sin\theta
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3. Permeability ():
Permeability is the measure of a material's ability to conduct magnetic flux.
Formula:
\mu = \mu_0 \cdot \mu_r
Unit: Henry per meter (H/m).
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4. Hysteresis Loop:
Represents the relationship between magnetic flux density () and magnetic field intensity () for a ferromagnetic material.
Key features:
Retentivity: Magnetic flux density when .
Coercivity: Field intensity required to reduce to zero.
Area of the loop: Indicates hysteresis loss.
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5. Reluctance ():
Resistance to magnetic flux in a magnetic circuit, analogous to electrical resistance.
Formula:
R_m = \frac{l}{\mu A}
Unit: Ampere-turns per weber (At/Wb).
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6. Leakage Factor:
The ratio of total magnetic flux to the useful flux in a magnetic circuit.
Formula:
\text{Leakage Factor} = \frac{\Phi_{\text{total}}}{\Phi_{\text{useful}}}
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7. BH Curve and Hysteresis Loss:
BH Curve: Graph of magnetic flux density () versus magnetic field intensity ().
Shows the magnetic properties of materials.
Hysteresis Loss: Energy lost per cycle of magnetization due to the lagging of behind .
Proportional to the area of the hysteresis loop.
Formula:
P_{\text{hysteresis}} = \eta B_{\text{max}}^n f
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8. Eddy Current Loss:
Loss due to induced currents in a magnetic material when subjected to a varying magnetic field.
Reduced by laminating the core.
Formula:
P_{\text{eddy}} = K_e B_{\text{max}}^2 t^2 f^2 V
