Development of a Long Life Uninterruptible Power Supply Using a Flywheel Energy Storage Unit.

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An uninterruptible power supply composed of a flywheel and a motor/generator for energy storage unit is developed. The main results obtained are as follows;1.The 10KW-1min. flywheel was designed and constructed for trial, but not yet examined by vacuum system accidents.2.For vacuum system improvements, the titanium getter was replaced by the good performance zirconium getter. From long term experiments, the vacuum was not maintained by leak through O-rings and the castg vessel.3.High efficiency of 93% was achieved by using switching loss recover circuits and amorphous core reactors.4.Short life electrolytic capacitors were replaced by small muF film capacitors by applying capacitor less inverter theories. The minimum value of capacitance can be decreased to 200muF in 10KW system having voltage build-up ability.5.By using high response current control of the PWM inverter, 99% input power factor and 2% output voltage distortion were obtained, simultaneously.7.Short life photo-couplers of the gate isolation were also removed by replacing pulse-transformers and transistor discharge circuits. As a result, the system will have over 15 years life.8.By use of direct torque control for motor/generator power, the sensorless drive of the flywheel was realized. It made a simple vacuum vessel and high speed power regeneration. All experimental data shown above present the validity of the flywheel use for energy storage units of uniterruptible power supplies.