Journal of international Conference on Electrical Machines and Systems

Journal of International Conference on Electrical Machines and Systems (대한전기학회 분과)
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Approaches to Suppressing Shaft Voltage in Non-Insulated Rotor Brushless DC Motor driven by PWM Inverter

  • Isomura, Yoshinori (Motor Business Division, Appliances Company, Panasonic Corporation) ;
  • Yamamoto, Kichiro (Dept. of Electrical and Electronics Engineering, Kagoshima University) ;
  • Morimoto, Shigeo (Dept. of Electrical and Information Systems, Graduate School of Engineering, Osaka Prefecture University) ;
  • Maetani, Tatsuo (Motor Business Division, Appliances Company, Panasonic Corporation) ;
  • Watanabe, Akihiko (Motor Business Division, Appliances Company, Panasonic Corporation) ;
  • Nakano, Keisaku (Motor Business Division, Appliances Company, Panasonic Corporation)
  • Received : 2013.12.27
  • Accepted : 2014.02.11
  • Published : 2014.09.01
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Abstract

The voltage source PWM inverter generally used to drive the air conditioning (A/C) fans has been posing a large issue that the bearings in air conditioning fan motors are highly possible to be corroded electrically. Potential difference called shaft voltage is generated between inner and outer rings of the bearings due to inverter switching. The shaft voltage causes bearing lubricant breakdown dielectrically. As a result, bearing current is caused. This current causes the bearing corrosion. In previous work, we demonstrated that the shaft voltage can be reduced by using an insulator inserted between the outer and inner cores of the rotor in an air conditioning fan motor without grounding. This paper proposes the other countermeasure for reducing the shaft voltage in fan motors. The countermeasure which adds a capacitor between the brackets and the stator core is effective even for fan motors with non-insulated rotor. The effectiveness is confirmed by both simulated and experimental results.

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References

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