Flywheel system properties are enhanced with rim designs that control stress at operational rotational velocities. The tensile strength of fiber-resin composites can be aligned with radial forces to improve radial stress loading. Loops with composite casings can be arranged around the flywheel circumference with a majority of the fibers being aligned in the radial direction. The loops can enclose masses that contribute to energy storage in the flywheel system. The masses subjected to radial forces can provide compressive force to the loops to contribute to maintaining loop composite integrity. With the alignment of fibers in radial directions, higher loading permits increase in rotational velocities, which can significantly add to the amount of energy stored or produced with the flywheel.

When a duration of current noise caused by a PWM control of each excitation amplifier is Td, a cycle of a PWM carrier signal is Tpwm, an on-duty upper limit of the PWM carrier signal under quiet environment without disturbance is Tonu, and an on-duty lower limit of the PWM carrier signal under the quiet environment without the disturbance is Tonl, the AD sampling period includes a first AD sampling period between a point after a lapse of the time Td after a start of the cycle Tpwm and a point after a lapse of a time (TpwmTonu) from the start of the cycle Tpwm, and a second AD sampling period between a point after a lapse of a time (TpwmTonl+Td) from the start of the cycle Tpwm and an end point of the cycle Tpwm.