Matsushita Electric Industrial Co., Ltd.

Yasuo Iijima

Masahiro Tsubokawa

Tokihiko Shimizu

Masaru Odagiri

Koichi Shinohara

Toshiaki Kunieda

Takashi Fujita

Yoshihiro Matsuda

Makoto Kusano

A voltage value of an impulse voltage repetitively applied on a test-piece coil is increased in accordance with time elapse. A terminal voltage applied on both ends of the test-piece coil is monitored to detect an electric breakdown of the test-piece coil. Upon detecting such a breakdown, application of the impulse voltage is immediately stopped to prevent the test-piece coil from being unnecessarily damaged. Meanwhile, a voltage value of the impulse voltage is measured quantitatively at the time the electric breakdown is detected and the measured data is stored in a memory, so that the memorized data can be used later as a breakdown voltage value.

Insulation testing method and apparatus therefor

A method of nondestructive insulation testing is disclosed which comprises the steps of: (a) placing an electric device, having a core and at least one winding provided on the core, in a reduced atmospheric pressure; (b) insulating the laminated core from the ground; (c) supplying a voltage signal having a first surge waveform to the winding; and detecting a glow discharge which may result from step (c) to detect an insulation condition of the winding, wherein the reduced atmospheric pressure ranges from 65 to 75 Torr and the voltage signal is applied in the first direction of the winding and then, is applied in the second, opposite, direction of the winding. This method may further comprise steps of: (d) supplying a second voltage signal having a second predetermined surge waveform having a peak voltage lower than a peak voltage of the predetermined surge waveform; (e) outputting a second output signal between the winding indicative of a second insulation condition of the winding in response to step (d); (f) measuring intervals corresponding to the wavelengths of the output signal and the second output signal respectively; and (g) judging the insulation condition by comparing the measured intervals to each other. A nondestructive insulation testing apparatus is also disclosed.

Method of nondestructive insulation test and a nondestructive insulation

A high speed dynamic run-out testing apparatus includes a drive source rotatable at a high speed and having an output shaft, a main shaft coupled coaxially with the output shaft of the drive source, a non-contact bearing for rotatably supporting the main shaft in a non-contact fashion, a testpiece carrier shaft provided on one side of the main shaft remote from the drive source for supporting a cylindrical testpiece mounted on such testpiece carrier shaft, and a non-contact displacement detector for measuring a displacement of the cylindrical testpiece.

High speed dynamic run-out testing apparatus and method

To carry out a non-destructive test for testing insulation of a small-size electric machine having a coil, a surge voltage is applied to the coil of the electric machine mounted in a decompression tank whose inner pressure is kept from 15 to 25 [Torr] so as to generate glow discharge in case there exists a flaw in the coil.

Surge testing method in decompressed atmosphere for a small-size

A magnetic recording medium wherein a ferromagnetic substance consisting of Fe, Co, Ni or alloy thereof is vacuum evaporated and deposited on a substrate made of a plastic film or a sheet of non-magnetic metal. The thin ferromagnetic film has the columnar crystal structure, and the columnar crystals are coated with a layer of oxide of the ferromagnetic substance.

Magnetic recording medium

An oil-impregnated capacitor comprising a thin insulator sheet solely consisting of a plastic film and impregnated with an insulating oil, the aptitude of which is defined by both the oil absorption and the expansion coefficient of the film.

Oil-impregnated polypropylene capacitor

There is disclosed an oil impregnated electric device in which an element of the device is impregnated with a mixture of an arylalkane compound such as 1,1-phenylxylyl ethane and an organic phosphorus compound such as phosphate or phosphite. Such electric device has a high power density (i.e., capable of withstanding high electric field) and a high reliability.

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Takefu, Japan

Yasuo Iijima