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Kawasaki, Japan

Ohsawa A.,Japanese National Institute for Occupational Safety and Health | Nomura N.,Kasuga Denki Inc.
Journal of Electrostatics

We present an experimental demonstration of a prospective idea obtained from 2-D electrohydrodynamic simulations in which continuously emitting balanced positive and negative ions from corona ionisers can yield zero offset voltage. © 2013 Elsevier B.V. Source

Ohsawa A.,Japanese National Institute for Occupational Safety and Health | Nomura N.,Kasuga Denki Inc.
Journal of Electrostatics

In our previous work, the AC type of ionisers was employed to demonstrate a prospective theory obtained by numerical simulations in which continuously emitting quasi-neutralised positive and negative ions from corona ionisers can transport ions effectively to a charged object and yield zero offset voltage. In this paper, we show that this can also be applied to pulse-DC ionisers, resulting in significant improvements in the offset voltage as well as charge-decay times. In addition, we present an implementation method with an electronic circuit design to create such an ion emission from a pulse-DC ioniser. © 2015 Elsevier B.V. Source

Choi K.,National Institute of Occupation Safety and Health | Mogami T.,Kasuga Denki Inc. | Suzuki T.,Kasuga Denki Inc.
Review of Scientific Instruments

To detect electrostatic discharges generated by polymer granules within a metal silo, we developed a novel and simple electrostatic discharge detector that utilizes a photosensor. The novel detector consists of a photosensor module in a metal cylinder, an optical band-pass filter, a quartz glass, a power supply, an amplifier for the photosensor module, and a digital oscilloscope. In this study, we conducted experiments at a real pneumatic powder transport facility that includes a metal silo to evaluate the novel detector using polypropylene granules. To determine the performance of the novel detector, we observed the electrostatic discharge within the metal silo using a conventional image intensifier system. The results obtained from the experiments show that the novel detector worked well in this study. The signals obtained with the novel detector were identical to the electrostatic discharges obtained with the conventional image intensifier system. The greatest advantage of this novel detector is that it is effective even when placed under external lights. In addition, the influence of various optical band-pass filters on the performance of the novel detector was discussed. Our study confirmed that an optical band-pass filter with a center wavelength of λ 330 nm (λ 1/2: 315-345 nm) was the best performer among the optical band-pass filters used in this study. © 2014 AIP Publishing LLC. Source

Mogami T.,Ibaraki University | Suzuki T.,Kasuga Denki Inc. | Choi K.S.,National Institute of Occupation Safety and Health | Ikehata T.,Ibaraki University
Journal of Loss Prevention in the Process Industries

As a method to prevent or mitigate cone discharges in a specific section such as a large silo, we have developed a new feedback control-type ionizer system. The feedback control-type system is composed mainly of an ionizer, an electrostatic field strength meter, and computer control equipment. In this study, we evaluated experimentally the practical version of the feedback control-type ionizer system through several tests in a pneumatic powder transport facility. The specific charges of the falling pellets in the silo were also measured for 10 s using a Faraday cage. Polypropylene (PP) pellets with a mean particle size of 3 mm were used in this experiment. The results of the experiment revealed that the feedback control-type ionizer system had the following characteristics: (1) it is possible to control the performance of the ionizer with a supply current; (2) the electrostatic field strength in the loading pipe from the charged powder is reduced and maintained at near zero by using the feedback control-type system; and (3) the performance of the feedback control-type system is superior to that of others, such as the conventional AC- or DC-type ionizers. © 2009 Elsevier Ltd. All rights reserved. Source

Sugimoto T.,Yamagata University | Yamaguchi K.,Yamagata University | Yamaguchi K.,Showa Denko K.K. | Higashiyama Y.,Yamagata University | Nomura N.,Kasuga Denki Inc.
IEEE Transactions on Industry Applications

Real-time monitoring of the cure state of sprayed paint is important for industrial painting processes to determine appropriate leveling and drying times. Paints contain pigment, resin, solvent, and other additives. The solvent is generally conductive and is finally evaporated during the paint-curing process, which results in a change in the electrical properties of the painted layer, from conductive to insulative. Therefore, we propose a technique to measure the cure state of a painted layer from the change in its surface resistance. The measurement apparatus includes a corona charger and surface potential probes. The surface resistance can be estimated from the increase in potential during corona charging. The degree of cure Dc is determined as a function of the surface potential. Pencil hardness, which is a general measure of the degree of cure, was also measured for comparison. A linear relationship between Dc and the pencil hardness was determined for various paints, which suggests that the degree of cure can be monitored according to Dc estimated from surface potential measurements. © 1972-2012 IEEE. Source

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