ELECTRICAL INSULATION CHARACTERISTICS OF LIQUID-HELIUM UNDER HIGH-SPEED ROTATING FIELD

Electrical breakdown behavior of liquid helium was investigated under high speed rotating field, In the development of superconducting turbi ne generator it is essential to get the knowledge of electrical insula tion characteristics of liquid helium under high speed rotating field. When the current of the field magnet of a superconducting generator i s changed, changing magnetic field generates heat in the conductor and it causes bubbles in the liquid helium around the conductor The behav ior of the bubbles is affected largely by the buoyancy which is genera ted by the centrifugal force. Electrical breakdown behavior of the liq uid helium is strongly dependent on the gas bubbles in the liquid, Ele ctrical breakdown voltage between electrodes mas measured in a rotatin g cryostat with and without heater input for bubble formation. Decreas e of the breakdown voltage by the heater power was smaller in the rota ting field than that in the non rotating field.