The Revolution PQ recorder can compute interharmonics in real-time, and also record each one individually as a stripchart. Each harmonic and interharmonic group and subgroup, as defined by IEC 61000-4-7,…
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Monitoring Variable Frequency Drives
Variable Frequency Drives (VFDs) are increasingly common, especially with the push for energy efficiency (in residential applications) and better motor control (in industrial applications). Unfortunately, the gains made with VFDs…
Measuring PLC AMR Signals with the Revolution
Many AMR (automatic meter reading) systems rely on PLC (power line communication) signals for data transfer. These signals travel on the 60Hz distribution network and can be affected by power…
Interpreting Total Harmonic Distortion
Total Harmonic Distortion (THD) is a way of quantifying the amount of harmonic content in a voltage or current waveform. In addition to measuring the amount of distortion, THD can…
Measuring Frequency with PMI Recorders
Line frequency is the most tightly controlled parameter in the electrical distribution system. Since almost all generation in a region is connected essentially in parallel, the frequency is inherently synchronized…
Arithmetic vs. Vector Power
The basic formulas for RMS voltage, current, power, etc. in a simple single-phase circuit are well-defined and universal. For polyphase systems, the situation is more complex: in the 3-phase delta…
Measuring Voltage Unbalance
Voltage unbalance can cause severe heating in motors and large DC power converters and an increase in harmonic currents. Fortunately unbalance is easy to measure with PMI recorders and ProVision…
Computing Event Duration with Histogram Data
The cycle histogram is an important, but underused record type available with all PMI recorders. The histogram doesn't require any configuration, spans the entire recording session (no possibility of memory…
Optimizing Waveform Capture Triggering
Waveform capture is the highest resolution data available for PQ analysis and is often crucial in solving tricky issues. Successfully triggering on the waveform doesn't have to be tricky, though.…
RMS Capture Graph in ProVision
A little-known graph in ProVision, the RMS Waveform Capture graph, can actually be one of the most illuminating. In cases where interval graphs don't have enough detail, and raw waveform…
Computing Event Duration With Interval Data
Although interval (stripchart) data can show cycle max and min readings, it's not normally used to get the duration of an event like a sag – waveform capture, event capture,…
Harmonics from Periodic Waveform Capture
Harmonics are usually recorded as interval (stripchart) data in PMI recorders. Each desired harmonic is recorded as a min/ave/max stripchart trace, for each desired voltage and current channel. Although this…
