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ELEMENTS OF ELECTRICAL DESIGN

MAGNETIC CIRCUIT DESIGN

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MAGNETIZING CURRENT CALCULATION :

  • MAGNETIZING CURRENT FOR CONCENTRATED WINDING:

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Magnetizing current is given by:

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Rms value mag. current

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MAGNETIZING CURRENT FOR DISTRIBUTED WINDING:

  • SINUSOIDAL FLUX DISTRIBUTION:
  • magnetizing current is:

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  • Rms value of mag. Current:

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  • Total amp. Turns require:

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  • per phase mag. Current:

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MAGNETIZING CURRENT FOR DISTRIBUTED WINDING:

  • NON-SINUSOIDAL FLUX DISTRIBUTION:

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MAGNETIZING CURRENT FOR DISTRIBUTED WINDING:

  • NON-SINUSOIDAL FLUX DISTRIBUTION:

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MAGNETIZING CURRENT FOR DISTRIBUTED WINDING:

  • NON-SINUSOIDAL FLUX DISTRIBUTION:

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FIELD FORM FACTOR:

  • A flux passing from pole to armature does not confine itself over the pole arc, but also spread over the whole pole pitch.
  • the flux will distribute itself in air gap in such away that the total reluctance is minimum.
  • some times it is necessary to determine distribution of flux called field form.
  • field form is used to know commutation condition in dc machines & in ac machines it determines shape of voltage waveform.

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FIELD FORM FACTOR:

  • field form can be determined by:

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  • 1) carter’s fringe curve.
  • 2) flux plotting by method of curvilinear squares.

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FIELD FORM FACTOR:

  • 1) carter’s fringe curve:
  • there is no any difficulties to determine the flux density at any portion of armature lying under the pole shoe if we neglect saturation.

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FIELD FORM FACTOR:

  • 1) carter’s fringe curve:

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FIELD FORM FACTOR:

  • 1) flux plotting:

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FIELD FORM FACTOR:

  • 1) flux plotting by method of curvilinear square:

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AIR GAP FLUX DISTRIBUTION (FIELD FORM) FACTOR:

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HARMONIC ANALYSIS OF FLUX DISTRIBUTION CURVE:

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HARMONIC ANALYSIS OF FLUX DISTRIBUTION CURVE:

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ACTUA FLUX DISTRIBUTION CURVE:

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ACTUA FLUX DISTRIBUTION CURVE:

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ACTUA FLUX DISTRIBUTION CURVE:

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ACTUA FLUX DISTRIBUTION CURVE:

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ACTUA FLUX DISTRIBUTION CURVE:

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MAGNETIC LEAKAGE CALCULATION :

  • EFFECT OF LEAKAGE FLUX:
  • It is not possible to confine all the flux can be pass through a desired way.
  • some of the flux can not take place in desired path is called leakage flux.
  • due to leakage flux, total flux decreases.
  • so for the same flux more mmf is required.

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MAGNETIC LEAKAGE CALCULATION :

EFFECT OF LEAKAGE REACTANCE:

1) More excitation is required.

2) poor machine performance.

3) poor voltage regulation of ac machines.

4) poor commutation of dc machine.

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MAGNETIC LEAKAGE CALCULATION :

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SLOT LEAKAGE FLUX

It crosses the slot from one tooth to the next, linking with that portion of the conductors below it by returning through the iron.

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Leakage Permeance Of Parallel Sided Slot

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Cont…

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Specific Permeance of Tapered Slot

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Cont…

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Specific Permeance of Circular Slot

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Specific Permeance of Complicated Shaped Slots

1

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Cont…

  • 2

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Cont…

  • 3

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Cont...

  • 4

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Specific Permeance of Slot With Double Layer Winding

For Bottom coil side

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Cont…

For Conductor Portion

For Non-Conductor Portion

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Cont…

  • Total specific slot permeance corresponding to mutual flux

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Specific Permeance of Slot of Special Purpose Induction Motor