Validation Of Naval Platform Electromagnetic Tools Via Model And Full-Scale Measurements

Reliable EMC predictions are very important in the design of a naval platform's topside. Currently, EMC predictions of a Navy ship are verified by scale model and full-scale measurements. In the near future, the validation of software tools leads to an increased confidence in EMC predictions and (hopefully) removes the need for scale model measurements. In general, full-scale verification measurements will remain necessary, although perhaps fewer measurements will be required. The paper presents our topside design experience, from rough estimations 40 years ago, to analytical calculations and model measurements 20 years ago, to the numerically supported process as it is now. It shows the process of validating simulation tools with model and full-scale measurements. It also describes the challenges encountered and the deficiencies of commercial tools used now and the roadmap for Thales Naval Netherlands towards the integrated tools of the future

Lightning current tests on radars and similar structures

A lightning stroke presents a real challenge due to its potential to cause irreversible damage on electronics. Future systems are packaged in composite shielding materials, which give little or no protection with respect to the electromagnetic fields caused by a nearby strike. A direct lightning stroke is even a higher threat for densely packed electronics in composite housings. Our objective is to determine an appropriate level of protection for a direct stroke. From the military standard MIL-STD-464A - Severe Strike, peak currents of the discharge between 50 and 200 kA, for the A pulse, 2 kA for the B pulse and 200 to 800 Amps for the C pulse are re-created in a closed environment. Experiments have been carried out using a test setup that could duplicate these three discharge components on structures representative for radar housing

"Good-but-Imperfect" electromagnetic reverberation in a VIRC

Novel theoretical probability density functions (PDF) of electromagnetic fields inside reverberation chambers operating in a “good-but-imperfect‿ regime have been recently reported. The present work reports on the application and assessment of these PDFs using a non-conventional type of reverberation chamber, namely the Vibrating Intrinsic Reverberation Chamber (VIRC). A vector network analyzer was used in order to measure the complex field components. An electrically short dipole antenna was used as a receiving antenna. Five thousand frequency points were taken ranging from 200MHz (undermoded regime) to 4 GHz (overmoded regime), so one measurement every 760 kHz was performed. For each frequency, 200 samples of the real and imaginary part of the field were measured. Measurements confirm the fact that the novel PDFs are able to describe the occurrence of anomalous statistics in the VIRC

Using transfer ratio to evaluate EMC design of adjustable speed drive systems

This paper proposes a way to evaluate the conducted electromagnetic compatibility performance of variable speed drive systems. It is considered that the measured noise level is determined by two factors, the level of the noise source and the conversion efficiency of the propagation path from the source to the measurement equipments. They are corresponding to the two roles played by the converter. On the one hand, a converter provides the noise source and generates the noise current and voltage on the motor side with the cable and the motor. On the other hand, it acts as the propagation path with the DC bus and the rectifier to spread the noise generated on the motor side to the line side. The transfer ratio is defined as the ratio between the CM current on the motor side and the CM current on the line side. It can be used to evaluate the EMC design of a converter because it is independent of the cable and the motor. A simplified model is used to explain this characteristic. It can be measured when the converter is powered off. Verification is carried out by experimental results obtained from a 12-kVA laboratory system.\u

A remote sensor for electromagnetic personal safety monitoring

Abstract: Citizens are often afraid of electromagnetic fields. This creates a need for logging and quantifying the exposure to fields in the civil environment. An electromagnetic field strength sensor (from 1MHz to 1GHz) has been developed which is connected to a logging system and a modem. The systems output level is independent of frequencies i.e. follows the standards limit curve. It can be powered by solar cells. So it can operate without human interaction anywhere. The system can emit a warning when the exposure level is exceeded. In normal mode, it transmits the logged levels once per week to a central data collection system. This paper describes the design and operation of the system