Static energy meters can be forced to give misreadings due to conducted electromagnetic interference (EMI). In previous research cases lower and higher readings of static energy meters were observed. In this paper an overview of previously reported lab experiments is given and further analyzed. The various situations are showing errors in the energy readings with respect to a reference meter. Based on these findings measurements are done using a dimmer in combination with a series of compact fluorescent lightning (CFL) and light emitting diode (LED) lamps. This setup was powered using a non-distorted mains power supply created by a four-quadrant amplifier combined with a line impedance stabilization network (LISN) to create a stable line impedance. The setup creates a pulsed current waveform with a short rise time. By using various line inductances the slope of the pulse is lowered and a correlation between the inclination of the slope and the deviations of the static meters is shown.
Measuring magnetic fields of equipment under test at low frequencies which is received by loop antennas using an EMI receiver with small bandwidths takes much time and can even reach a week for a standard measurement. This waste in time could be avoided by applying time domain measurements. Commercial time-domain EMI (TDEMI) measurement equipment are sampling at the intermediate frequency, and are still relatively expensive. Base-band sampling using low-cost digitizers, or an oscilloscope, is proposed in this paper. The measured data is converted to the typical results in frequency domain via fast Fourier transform, while the necessary large dynamic range is achieved via oversampling. This methodology decreases the cost of the test equipment, but most of all reduces the measurement time drastically compared to the classical frequency domain measurement approach. The setup is described. Measurements with a conventional receiver parallel to the digitizer using a signal generator powering a radiating loop have been performed. Also measurements on an actual interfering source with pulsed magnetic fields are performed. It is shown that the measurement results are the same, while the measurement time has been reduced drastically.
This article presents a time-domain waveform model developed to characterize pulsed, nonlinear, current waveforms resulting in electromagnetic interference on static energy meters. The waveform model is calculated by fitting the sampled waveform data into a linear piece-wise function through a process that involves applying algorithms of pulse extraction, change-point detection, and redundancy elimination. The model is applied to data from laboratory experiments that have indicated critical current waveforms resulting in electromagnetic interference problems with static meters. Afterwards, the parameters of the modeled waveforms are calculated in order to correlate them to metering errors. The most relevant parameters that are correlated to significant errors are the maximum slope, crest factor, pulse duration, and charge. The waveform model provides an accurate description of the complex nonlinear waveforms through simplified analytical expressions that reproduce the significant features of the interfering waveforms. This waveform modeling approach could be used to standardize the artificial test signals that are representative of realistic devices and scenarios.
Safely measuring high power conducted electromagnetic interference (EMI) is an issue to be addressed, where a possible measurement strategy is being discussed in this paper which uses the benefits of multi-channel synchronous timedomain electromagnetic interference (TDEMI) measurements. Only the differential mode (DM) voltage has been evaluated in this paper, however the setup is not limited in this respect. Common mode (CM) voltage can also be synchronously analyzed with this setup. Nevertheless, with respect to the to be measured amplitudes, DM voltages in this particular system offer a larger challenge and are addressed. The setup was developed with respect to Low-Frequency conducted EMI measurements in high power, fast switching systems using a low-cost solution.
Readings of static energy meters can be affected by conducted electromagnetic interference (EMI). Previous research reported many cases where lower and higher readings of static energy meters were observed. In this paper experiments with a water pump, controlled by speed regulators, resulted in huge errors in energy readings of static meters with respect to a reference meter. The speed regulators are intended to be used in conjunction with such water pumps. The tests were performed using a non-distorted mains power supply created by a fourquadrant amplifier with an internal impedance in accordance with the standards. The deviations observed are between-91% and +175% compared to the reference meter. The current waveforms attributed to these large deviations show large spikes with rise times of a few microseconds.
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