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…
White Papers
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Power Quality
Understanding Vector Diagrams
This whitepaper will discuss what vector diagrams are, what they display, and how PMI's power quality recorders and ProVision can provide the user with this information.
Techniques for Analyzing Motor Startups
This paper covers the setup fundamentals and techniques required to obtain the high-quality waveform capture needed to analyze a motor startup. It also reviews the basic electrical characteristics of a…
Understanding Telephone Interference Factor
Harmonic distortion that is produced from power conversion systems can cause interference on analog telephone lines. The degree of telephone interference can be expressed in terms of the Telephone Interference…
CBEMA and ITIC Curves
The CBEMA and ITIC curves are both used to visibly represent voltage events. The terms and associated curves are used somewhat interchangeably even though there are subtle differences between the…
Voltage and Current Out of Limits Reports
This white paper covers Out of Limits Reports, their main benefits, and how and when to use them. Out of Limits Reports offer a quick way to gauge power quality…
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…
Daily Profile Graphs in ProVision
Daily Profiles are used to spot daily trends in voltage, current, power factor, etc. An entire recording session is combined to form the "average" 24-hour day, which is then plotted…
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.…
