Increase in operating range and efficiency for variable gap axial flux motors

Greg Heins, Mark Thiele, Dean Patterson, Nicholas Lambert

    Research output: Chapter in Book/Report/Conference proceedingConference Paper published in Proceedingspeer-review

    9 Citations (Scopus)


    For applications requiring a constant power source such as traction, efficient power electronic utilization requires an electric machine capable of flux weakening. Usually flux weakening is achieved by using an interior permanent magnet machine (IPM) and by applying current in the d-axis. Other recent work has used two inverters or pulses of current to demagnetize and magnetize the magnets depending on the operating point. This paper presents an axial flux machine with mechanical flux weakening capability. Experimental data shows that the torque constant can be reduced to five times its maximum value and the efficiency in the rated operating range can be increased by up to 15% points. To demonstrate the impact of the mechanical flux weakening mechanism on the efficiency of the system, the motor data was used to model the performance of an electric motorcycle over a World Harmonized Light Vehicles Test Procedures (WLTC)[1] drive cycle. If a self locking automated actuation mechanism is used, the peak power required by the actuation mechanism is 4% of the traction motor power rating and the energy used over the drive cycle is 0.05% of the traction motor energy use, suggesting negligible impact on the overall efficiency. If a non locking mechanism is used, the actuating power and energy will be substantially lower.

    Original languageEnglish
    Title of host publication2014 IEEE Energy Conversion Congress and Exposition, ECCE 2014
    PublisherIEEE, Institute of Electrical and Electronics Engineers
    Number of pages7
    ISBN (Electronic)9781479956982
    Publication statusPublished - 11 Nov 2014
    EventIEEE Energy Conversion Congress and Exposition (ECCE 2014) - Pittsburgh, United States
    Duration: 14 Sept 201418 Sept 2014
    Conference number: 2014


    ConferenceIEEE Energy Conversion Congress and Exposition (ECCE 2014)
    Abbreviated titleECCE
    Country/TerritoryUnited States
    Internet address


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