A discharge current waveform for air discharge immunity testing is well-known to be significantly affected by many factors such as approach speeds, ambient temperature (T) and relative humidity (RH), as a matter of fact, it is not widely recognized that an essential affecting factor is the resultant spark length itself. For clarifying the effect of the approach speeds and climatic conditions on air discharge testing, we previously measured air discharge currents from an electrostatic discharge (ESD) generator with test voltages from 2 kV to 15 kV at two different approach speeds of 80 mm/s and 20 mm/s under 6 combinations of T and RH in the IEC specified range and non-specified climatic range. The result showed that at a test voltage of 15 kV under the IEC specified climatic conditions over RH 30%, the 20 mm/s approach speed yields the current waveforms entirely different from those at 80 mm/s despite the same absolute humidity (AH) conditions, and that the peaks are basically unaffected by the AH. Under the IEC non-specified climatic conditions with RH not greater than 20%, however, as in the case of 80 mm/s, the peaks decrease at higher test voltages when the AH increases. In this study, to investigate how the above findings can be derived, we estimate the spark lengths for air discharges of an ESD generator at test voltages from 2 kV to 15 kV from the measured discharge currents under the IEC specified and non-specified climate conditions with respect to two different approach speeds of 80 mm/s and 20 mm/s. As a result, on the same AH conditions, regardless of the approach speeds, the spark lengths under the IEC non-specified conditions (higher temperature or lower relative humidity) are shorter than those under the IEC specified conditions, which yields a higher current peak. A relationship between the spark lengths and the current peaks is deterministically given by a single curve according to the test voltage regardless of the approach speeds and climatic conditions, and the coordinates on the curve change depending on an approach speed, ambient temperature and absolute humidity.
When a magnetic levitation rail carrying a superconducting coil moves at high speed, an electromagnetic induction voltage is generated in the surrounding telecommunication line due to Faraday’s electromagnetic induction. This phenomenon is analyzed by AC / DC module of COMSOL Multiphysics. The telecommunication line is modeled for a common mode flowing in a loop between the telecommunication line and the ground. As a result of examining the structure dependency on the induced voltage of the telecommunication line loop, if there are two bogies, It was clarified that the induced voltage becomes a voltage close to zero if the length of the telecommunication line is equal to the bogie interval, and a voltage twice the normal induced voltage is generated when the length of the telecommunication line is slightly shorter or longer than the bogie interval.
In this paper, the influence to electromagnetic environment was evaluated on the outside of buildings where power line communication (PLC) systems were installed to a three-wire three-phase power distribution line. The electric field strength was measured at 140 points in five factories, in two office buildings, and in one stadium. Since many radio waves existed in the environment, the electric field strength when PLC system was operated and was not operated was measured. The influence was evaluated by the cumulated occurrence probability because the frequency characteristics of the electric filed strength changed by the measurement points. The results showed that the occurrence probability was not changed when the PLC system was operated and was not operated. The electric field strength was calculated by the common mode current obtained from the test result, and this indicated that the occurrence probability was lower than the measured occurrence probability of electric field strength.
Fast switching operation of Silicon carbide (SiC) and Gallium nitride (GaN) power semiconductor devices could be a severe electromagnetic interference (EMI) noise source of high-voltage power converter. This paper experimentally evaluates the dynamic characteristics of SiC and GaN power transistor in synchronous rectification DC-DC converter and characterized it as an EMI noise source. The results suggest that the characteristics of unipolar device of SiC MOSFET (metal-oxide-semiconductor field-effect transistor) and GaN HEMT (high-electron-mobility transistor) show large-amplitude and slow-damped ringing oscillation in the switching waveform. It will influence on the EMI level of power converter in several tens of megahertz range.
In recent years, measurement methods for large-scale systems composed of multiple devices have been discussed mainly by the CISPR (Comité International Spécial des Perturbations Radioélectriques) subcommittee B. For example, DC/DC converters, which are component of photovoltaic system, are usually composed of a large number of units, and an AC/DC converter is required for connection to AC power grids. The limits and measurement methods for electromagnetic noise of a DC/DC converter and AC/DC converter are specified in the international standard CISPR 11. Since it is difficult to measure the conducted disturbance of an individual devices in a system composed of multiple devices, another method by measuring the radiated magnetic field should be examined. However, radiation measurement using a turntable in a test site is difficult in a case of large-scaled system. In such cases, an alternative method for radiated emission measurements is required. In this paper, the common-mode current, magnetic field, and electric fields radiated from an equipment under test that assumed a large-scale system consisting of many DC/DC converters and an AC/DC converter are measured and the electromagnetic characteristics are analyzed. By comparing the results of the conventional measurement method and of the proposed alternative method, it was confirmed that the peak frequencies of the spectrum coincided with each other, although the level of the electromagnetic noise was different. As a result, if the relationship between the measurement distance and the emission level was clarified at an appropriate measurement point, it was found that the proposed method was applicable for an alternative measurement method.
In this study, the internal (in situ) electric field induced in human tissues by ELF and intermediate frequency uniform magnetic fields has been determined using the scalar potential finite difference (SPFD) method. These calculations were conducted on adult Japanese numerical models and the calculation results were compared with the DRL (dosimetric reference limits) provided in the IEEE safety standard. Under the ERL (exposure reference levels) condition defined in the IEEE C95.1TM-2019 standard, the calculated internal electric fields exceeded the DRL in the cases for certain body parts and conditions.
When a shielded-twisted-pair (STP) cable is connected with a printed circuit board (PCB) via an Ethernet (RJ45) connector, mode conversion between primary- and secondary-common modes occurs at the connector section due to their structural difference that causes the difference in the imbalance factor of the transmission line. In this paper, we investigate the suppression of the mode conversion at the connector section by using a modal-equivalent circuit model based on imbalance matching. We focus on improving the PCB pattern below the shielded Ethernet connector by placing a copper layer on the PCB surface, and the inadequate shielding at the connector section by soldering and wrapping with copper tape. The application of this improvement based on imbalance matching at the connector section makes the imbalance factor of the connector section closer to that of the cable section and results in the suppression of the mode conversion. Based on the concept of imbalance matching, we confirmed the effect of the shield-improved connector with an improved PCB pattern on the suppression of the mode conversion at the connector section through circuit simulation and measurement, and it was validated that the circuit simulation results obtained from the modal-equivalent circuit model agree well with the measurement results.
Measurements of discharge current waveforms are conducted for the air discharges from a charged human with voltages of ± 4 kV and ± 8 kV to estimate the spark lengths. The result shows that a specific relationship holds between breakdown potential gradients and discharge current peaks regardless of charging voltages, their polarities, approach speeds and climatic conditions.
Circuit parameters of microstrip lines (MSLs) covered by noise suppression sheets (NSSs) with different geometries were estimated by magnetic circuit analysis and electromagnetic field simulation. The estimated circuit parameters, resistance and inductance, were almost the same with measured values below the wavelength resonance frequency, respectively. This result indicates the feasibility to design the MSL with the NSS using those geometries.
An ESD (electrostatic discharge) event generates impulsive electromagnetic fields and causes a source of wide-band electromagnetic noise. To discuss the EM radiation mechanism due to ESD, transient magnetic fields were measured to consider the distance characteristics of peak value of the fields. It was confirmed that the transient magnetic field attenuated by the inverse square of distance in a nearby spark gap, while in inverse proportion to the distance in the far distance. This result is considered to suggest that the EM radiation model due to ESD is explained by the dipole antenna model which has a metallic radiating structure of the spherical electrodes.
Transient electric fields due to collision electrostatic discharges (ESDs) between charged spherical electrodes with a diameter of 30 mm at a charging voltage from 600 V are measured in the close proximity to the spark point by using a bare-chip optical electric field sensor. The transient responses of the electrostatic fields at distances of over 6 mm away from the spark point are also shown.
Assuming the close proximity radio frequency immunity test using impulsive electromagnetic waves, the validity of an exponentially-tapered TEM horn antenna as a radiator was examined. In this paper, the transient magnetic field distribution at the aperture of the antenna due to impulse wave excitation was measured in time domain. As a result, the uniformity of the transient magnetic-field distribution almost agreed with the measured result in frequency domain.