BLDC Chapter 4. Brushless motor fundamentals

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BLDCChapter 4. Brushless motor fundamentals
2006. 2. 15 ???
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4.1 Assumptions

• 1. Rotational Motion
• ? ??? ?? ? ???? stator??? ??? rotor? ?????
  ??.
• 2. Surface-Mounted Magnets
• ???? BLPM???? ??? ??? ??? ?? ???, ??? ???
  ??. ?? ????? ??? ??? ? ?? ?? ?? ?? ??? ??.
• - ??? ?? ?? ?? ??
• ?? ??? ????.
• ??? ????? ? ? ????.
• ????? ??? ? ?? ???? ??? ????.

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4.2 Fundanmental concepts
1. Magnetic Circuit Model - ??? ??
Flux? N??? ?? stator? ??? S?? ???? ??? stator?
??? ?? ?? S?? ???? ??? ??. stator? ??? ?? ???
??????(magent leakage flux)? ???. ???? ???? ???
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4.2 Fundanmental concepts
- ?? ?? ??
magnet reluctance air gap reluctance
leakage reluctance flux source
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4.2 Fundanmental concepts
- ???? ????
??? ??? rotor reluctance(Rr)? ??????? ??(a)?? ??
? ??.
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4.2 Fundanmental concepts
Leakage flux ? air gap flux ? ?? ?? ???
??? ? ??.
??? Leakage flux? ???? ??? leakage factor
? ????. Air gap flux? ? ??? ?
??, leakage factor ? ????? 1?? ?? ?? ???.
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4.2 Fundanmental concepts
?? ??? ? ??? ??? ??? ??? 2?? ??? ??? ?? ???
? ????, ? 2?? ??.
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4.2 Fundanmental concepts
Steel reluctance ? air gap reluctance
? ?? ????? ????, ??? ? ??. ??? steel
reluctance? ???? ?? reluctance factor ?
????. Reluctance factor ? 1?? ?? ? ???.
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4.2 Fundanmental concepts
2. Magnetic circuit solution (from ??(d))
- magnet flux (from ????)
- magnet and air gap reluctances
- air gap flux
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4.2 Fundanmental concepts
- air gap flux density
flux concentration factor permeance
coefficient
????? leakage factor? ,
reluctance factor ? ? ??
???. Flux concentration factor ? ????? ????,
1? ??. ? ??? ??? ?? ????, ? ? ??? ????.
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4.2 Fundanmental concepts
- ??? ? air gap flux density? permeance
coeffient? ??
Permeance coeffient? ?? ????, ??? ? air gap flux
density? 1?? ?? ?? ?? ????. ???? ????? permeance
coefficient? 46? ?? ???.
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4.2 Fundanmental concepts
- ???? ?? air gap flux density
Air gap flux density? N???? ????, S???? ????
???. ??? ??? ??? ??, ??? ????? 1?? ?? 2??? ?? ??.
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4.2 Fundanmental concepts
3. Flux linkage
- ??? full-pitch coil? ??? ?? ?? (??? 0?)
2?? slot? ???? ??? N? ???. ??? ??? flux ??? ???
??? ??? ??? flux? ??? ?????, flux linkage? ??? ??.
Coil pitch
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4.2 Fundanmental concepts
- ??? 90? ??? ??
Flux linkage? ? ??? ??? ???, ??? ?????, ?? 0??.
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4.2 Fundanmental concepts
- ??? 180? ??? ??
??? 0???? Flux linkage ??? ???, ??? ????.
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4.2 Fundanmental concepts
- ??? ??? ?? flux linkage and back EMF
???? 0??? 360??? ???, ??? ??? ??? ???.
???? 0??? 360??? ???, ??? ??? ??? ???.
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4.2 Fundanmental concepts
4. Back EMF and Torque
- Back EMF (from Faradays law)
- Air gap flux
Carters coefficient? ???? ??? ??. Angular pole
pitch (radM) Air gap radius at magnet
surface Axial length of the motor
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4.2 Fundanmental concepts
- Back EMF? ?? (from ?? ? ? ??)
Back EMF constant ( V/(radM/s) )
- Torque? ?? (from 3.43)
Torque constant (Nm/A ) ??? ??? ??
- ? ? ??
? ? SI??? ????? ??? ?? ?? ???.
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4.2 Fundanmental concepts
- ?? ??? flux linkage, back EMF, torque ??
?? ????? ????? ?? ??? ??? ?? ???, ??? ??? ?? ?
??. ????? ???? ? ?? ??? ? ? ??.
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4.2 Fundanmental concepts
5. Multiple coils
- 4?? full-pitch coil? ?? ??
????? 1?? full-pitch coil? ?? ??? ?????? ??? ???
??? ????? ?? 2?? slot? ???? 3?? full-pitch coil?
??? ????. ??? coil? ??? phase winding or phase?
???.
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4.2 Fundanmental concepts
- Back EMF? ?? ? ??? back EMF? ??? ?? ?? ???, ??
back EMF? ??? ??? ??.
- Torque? ?? ?? ?? ??? ??? ??.