TY - GEN
T1 - Suspension force model for bearingless AC homopolar machines designed for flywheel energy storage
AU - Severson, Eric
AU - Nilssen, Robert
AU - Undeland, Tore
AU - Mohan, Ned
PY - 2013
Y1 - 2013
N2 - Bearingless ac homopolar machines combine magnetic bearing and motor/generator functionality into a single electric machine which features variable excitation, high power density at high rotational speed, a simple and robust rotor structure, and magnet-less excitation. These features make the bearingless ac homopolar machine a promising machine for highspeed flywheel energy storage systems (FESS). The variable excitation of the bearingless ac homopolar machine has the potential to increase the FESS's efficiency by allowing for low excitation during periods of free-wheeling and high-speed operation. However, the magnetic suspension's position stiffness and current stiffness depend upon the excitation level. This dependency must be taken into account in the suspension controller or the magnetic suspension may become unstable at certain excitation levels. A technique for modeling this dependence is presented in this paper and explored through 3D finite element simulation. A prototype design is analyzed for two rotor structures: one with a square airgap length profile and one with an inverted sinusoidal airgap length profile.
AB - Bearingless ac homopolar machines combine magnetic bearing and motor/generator functionality into a single electric machine which features variable excitation, high power density at high rotational speed, a simple and robust rotor structure, and magnet-less excitation. These features make the bearingless ac homopolar machine a promising machine for highspeed flywheel energy storage systems (FESS). The variable excitation of the bearingless ac homopolar machine has the potential to increase the FESS's efficiency by allowing for low excitation during periods of free-wheeling and high-speed operation. However, the magnetic suspension's position stiffness and current stiffness depend upon the excitation level. This dependency must be taken into account in the suspension controller or the magnetic suspension may become unstable at certain excitation levels. A technique for modeling this dependence is presented in this paper and explored through 3D finite element simulation. A prototype design is analyzed for two rotor structures: one with a square airgap length profile and one with an inverted sinusoidal airgap length profile.
KW - ac homopolar machine
KW - active magnetic bearing
KW - flywheel energy storage
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U2 - 10.1109/IEEEGCC.2013.6705789
DO - 10.1109/IEEEGCC.2013.6705789
M3 - Conference contribution
AN - SCOPUS:84893626168
SN - 9781479907243
T3 - 2013 7th IEEE GCC Conference and Exhibition, GCC 2013
SP - 274
EP - 279
BT - 2013 7th IEEE GCC Conference and Exhibition, GCC 2013
T2 - 2013 7th IEEE GCC Conference and Exhibition, GCC 2013
Y2 - 17 November 2013 through 20 November 2013
ER -