To quicken the arrival of the time point when a residual voltage of an induction motor is quickly eliminated so as to allow re-excitation when putting the induction motor into a non-excitation state in a free rotation state by flywheel inertia.
When putting a flywheel 9 into an idling state by stopping excitation of an induction motor 10 in a state where inertial energy is accumulated by rotating the flywheel 9, an induction voltage is not instantaneously put into a zero voltage but an excitation voltage is reduced in a ramp-shaped manner by taking time. By this, a residual voltage generated by a residual magnetic field occurring in the induction motor 10 is consumed after converting it into thermal energy or the like by a flywheel inverter 11 while the excitation voltage is reduced to a zero voltage. Consequently, when the excitation voltage is reduced to a zero voltage, it is already in a state in which the residual voltage of the induction motor 10 generated by the residual magnetic field is eliminated.
COPYRIGHT: (C)2009,JPO&INPIT
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Iwa Saki Kokuni
Kawamata Sumio
Masakazu Ito
Shunichi Takahashi
Toshio Takamatsu