Norimitsu Ichikawa

Electrostatically induced voltage generated in "metal boxes with different volume" measured by spark gap and electromagnetic wave sensor

The movement of a charged body, such as a charged human body or a charged device, often causes a malfunction or failure in an electronic apparatus because an induced voltage is generated in a partially opened metal box of the apparatus. We cannot ignore this type of electronic apparatus malfunction when the relative humidity in a room decreases because of the use of an air conditioner. We need to design the electronic apparatus to safely prevent such malfunctions. The induced voltage generated in the metal box must be measured for the safe design of an electronic apparatus. We measure the induced voltage generated in the metal box without electrical connections using a spark gap and an electromagnetic wave sensor. In this paper, we study the relationship between the induced voltages and the volume of the metal boxes. Five metal boxes with different depths are used to vary the volume of the boxes in the experiment. The measured result shows that the induced voltage generated in the metal box is independent of the volume of the metal boxes (the depth of the boxes). Thus, the value of the induced voltage generated in a small metal box is almost the same as that in a big metal box. Therefore, an induced voltage can be generated in a small metal box, such as a tablet device. The result of this study is useful for the safe design of an electronic apparatus to prevent malfunctions and failure of the apparatus.

Electrostatically induced voltage on conductive objects contained in metal box when charged body moves away from the box

Electrostatically induced voltage generated on printed circuit boards in a grounded metal box occasionally causes a malfunction and failure of the electronic equipment. A person who walks into a room that has an air conditioner can be electrified up to -10 kV or more. However, a microelectronics device malfunctions by an occurrence of induced voltage of less than 10 V. In the present paper, the induced voltages on an ungrounded one of two conductors that are contained in the metal box are measured and calculated when a charged body moves away from a partially opened metal box. The induced voltages are measured by the use of a spark gap and an electromagnetic wave sensor and are compared with the results from an electrostatic voltmeter. The induced voltages are calculated, moreover, by the use of q=cv, with the capacitances and charges. The results show that the induced voltages of -42% of the voltages of the charged body are generated in the metal box when a charged body moves away from the metal box. The results will be helpful in considering preventive measures of the malfunction and failure of electronic equipment.

Electrical Fatality Rate by Industry in Japan, 1974–2003

Fatal accidents caused by electric shock have been occurring since electricity was first introduced. Overall, the number of fatal accidents is decreasing. However, the decrease in the number of fatalities has slowed in recent years. A statistical study is needed to reconsider the preventive measures against these accidents. In this paper, the trend of fatalities by accident type and industry in Japan is studied statistically. These results show that the electric fatality rates differ by industry. The fatalities in the construction and the electrical-construction industries make up approximately 60% of the total fatalities. In addition, the accident type is most frequently contact with electrical lines by either the human body or a tool. In these industries, the elimination of fatal accidents from shocks is an important subject. These results will be helpful in preventing fatal accidents by electric shock.

Japanese trends in fatal accidents caused by electric shocks and the prevention of the accidents

Fatal accidents in Japan caused by electric shocks have been occurring since electricity was first introduced. Overall, the number of fatal accidents is decreasing. However, the decrease in the number of fatalities has slowed in recent years. A statistical study is needed to eliminate the accidents. In this paper, the trend of fatalities as a function of the accident type is studied statistically for Japan. The results show that the number of fatalities from high-voltage exposure become smaller than those from low-voltage exposure during the 30 years studied. The fatalities in the construction industry (electrical construction industry and construction industry) make up approximately 80% of the total fatalities. For the construction industry, the elimination of fatal accidents from shocks is an important subject. The results will be helpful in preventing fatal accidents from electric shocks not only in Japan, but also all over the world.

Experimental consideration of the electrostatically induced voltage generated when a charged body approaches a metal box and moves away from the box

Electrical equipment within a metal box may malfunction due to an electrostatically induced voltage. The voltage of the metal box is induced by the movement of a charged body, such as a charged human body. When the charged body approaches the metal box and moves away from the box, the induced voltage of the metal box generated by the movement of the charged body is experimentally studied in this work. In the experiments, the depth of a metal box is changed, and the result shows that the induced voltage of the metal box when the charged body moves away from the box is approximately −4 times the value of the induced voltage when the body approaches the box in this experimental condition. These results will be useful in designing electrical equipment capable of preventing equipment malfunction and failure.

Statistical accident analysis and electrical fatality rate in Japan, 2002–2011 - Causes and preventive measures of fatal electrical accidents

Among the occupational accidents, over 7,400 electrical fatalities occurred between 1958 and 2003 in Japan. Approximately 60% of all electrical fatalities occur at work in the construction industry, which includes the electrical construction industry. If the number of electrical fatalities in the construction industry is reduced, almost all fatalities are eliminated. The number of annual fatalities has never been zero, but it has slowly decreased. We cannot reduce it further if the technology of insulating safeguards and safety training is not improved. In previous studies, we reported the electrical fatality rate by industry and the type of fatal accidents in Japan from 1974-2003. This analyses were performed using of data from the Ministry of Health, Labor and Welfare (MHLW) and the Japan Industrial Safety and Health Association (JISHA). In addition, some preventive measures and the number of monthly fatalities were reported. These results are useful for us to prevent the fatal accidents caused by the occurrence of electric shock. In the present paper, we report the statistical results of the details of causes, contacted part of the human body, company size, and so on for fatal electrical accidents during 2002-2011 in Japan. The results show that almost all fatal accidents by electric shock occur when the company size is fewer than 50 workers. The use of metal necklaces and other metal accessories increases the number of possible accidents. Thus, a detailed analysis is performed to prevent such accidents. The results of the present study will be helpful to consider new preventive measures of electric shock.

Experimental consideration of electrostatically induced voltage generated by approach and isolation of charged body

Electrical equipment within a metal box may malfunction by an electrostatically induced voltage. The induced voltage of the metal box is changed by the movement of a charged body, such as a charged human body. The induced voltage of the metal box generated by the approach and isolation of the charged body is experimentally studied in this work. In the experiments, the depth of a metal box is changed, and the result shows that the induced voltage of the metal box generated by the isolation of the charged body is higher than that generated by the approach of the body. The former induced voltage of the metal box becomes the voltage of approximately -400% of a latter induced voltage in this experimental condition. Electric charges of metal boxes are somewhat dependent of the depth of the boxes. These results will be useful to design electrical equipment capable of preventing equipment malfunction and failure.

Three hundred forty-nine case studies and their consideration of electrical accidents in Japan

The continuation and improvement of preventive measures and safety training following electrical accidents are important in reducing the number of accidents in the workplace. A consideration of these preventive measures based on case studies of electrical accidents is required. Consideration may not be sufficient in Japan and other countries, because many electrical accidents involve electric shocks. Thus, continuation and improvement of electrical safety measures are needed. Several research papers on electrical accidents in the workplace have been published; however, a detailed consideration and analysis of case studies are also important, because safety culture and electrical installation differ by country. The use of less than 35-V products and equipment may be needed for thorough prevention of fatal electrical accidents. There are some differences in voltage level by country, which may cause a problem in ultimately reducing the number of accidents. In this study, 349 cases were considered. An assessment of electrocutions has never been performed in Japan; therefore, this paper will summarize the circumstances of electrocutions in Japan based on industry statics. It is the authors expectation that the results will assist in developing possible engineering solutions to reduce electrical accidents.

Investigation of human body potential measured by a non-contact measuring system

A human body is occasionally electrified in a room. This charged object will be a source of electrostatic accidents, including the malfunction of electronic equipment. Hence, prevention of these accidents is required. Accidents occasionally occur, even though antistatic clothes and shoes are used. One of the causes for these accidents is that there is a lack of the preventive measures. This situation occurs when using, for example, unconductive wax. In this study, human body potential (voltage) is measured using a non-contact measuring system. An investigation of the human body’s voltage when using this system is conducted. The result demonstrates that the voltage of a human body wearing antistatic clothes and shoes or light clothes and slippers exceeds a malfunctioning voltage of a microelectronics device when the body walks on floors. Thus, accidents may occur even if a human body wearing the antistatic clothes walks on flooring. These results will be useful in estimating determination whether electrostatic accidents occur or not.

Electrical Fatality Rates in Japan, 2002-2011: New Preventive Measures for Fatal Electrical Accidents

The statistical results of the causes, body contact points, and company sizes for the workplace are reported for fatal electrical accidents from 2002 to 2011 in Japan in this article. The results show that 81% of all fatal accidents by electric shock occur when the company size is fewer than 50 workers. The assignment of a safety supervisor is not obligatory for a company of this size. Contact between a hand or tool and a charged object accounts for 58% of all fatal accidents. Most fatal accidents are caused when a hand contacts the low- or high-voltage segment of a live wire. A total of 7,569 workers died from electric shock accidents between 1959 and 2011 in Japan. The data show that wearing metal necklaces and other metal accessories increases the potential for accidents. Thus, a detailed analysis was performed to prevent such accidents. Knowledge about these fatal accidents is required to develop various protective devices and safety regulations and acts. The results of this study will be helpful in considering new preventive measures for electric shock.