Fuji Electric Co., Ltd.

Yukio Osawa

Toshio Kobayashi

Mamoru Yamada

Hisaji Shinohara

Tadao Kitamura

Masayuki Furusawa

Kazuro Shibata

Noboru Usui

Shoichi Ote

Katsuhiko Taguchi

Nobuyuki Odaka

Interrupting and chopping characteristics of a Cu--Cr contact alloy are improved by rounding Cr particles to be spherical in the alloy. The Cr particles are rounded in the alloy by sintering raw Cr powder particles having an average particle diameter of less than 100 .mu.m at a temperature of 1,100.degree. C. or higher with Cu powder, or by sintering raw Cr powder particles having an average particle diameter of 100 to 150 .mu.m at a temperature of 1,200.degree. C. or higher with Cu powder.

Contact material for a vacuum circuit breaker and a method for

An improved vacuum valve including an insulating container and an arc shield held in the insulating container, wherein a protrusion is formed on either the outer cylindrical surface of the arc shield or on the inner surface of the container. A detecting electrode is set confronted with the outer surface of the insulating container with an air gap therebetween, and is grounded through a current sensor. The current sensor detects a discharge current which is induced through the protrusion when the degree of vacuum of the vacuum valve is reduced, to output a detection signal. In response to the detection signal, a signal processing unit outputs an alarm signal indicating the reduction in the degree of vacuum of the vacuum valve. Thus, while the vacuum valve is in operation, its vacuum reduction can be positively detected with the vacuum valve maintained unchanged in reliability.

Method and apparatus for detecting a reduction in the degree of vacuum

Growing community of inventors

Kawasaki, Japan

Yukio Osawa