ACWF.js is an analysis library for alternating current waveforms.
Alternating current (AC) waveforms (WF) carry three-phase electrical power to commercial and industrial customers. The library was written with the intent of providing visualizations of waveforms and analysis results using charts and plots. There are a number of standard JavaScript charting libraries available that can handle displaying waveforms and harmonics; jqPlot and jqChart are typical examples. There did not seem to be any that included a chart type suitable for a phasor diagram. ACWF.js includes a simple HTML5 canvas phasor diagram plotting component.
<html>
<head>
<script type="text/javascript" src="dsp.js"></script>
<script type="text/javascript" src="acwf-core.js"></script>
<script type="text/javascript" src="acwf-canvas.js"></script>
<script type="text/javascript" src="sample-data.js"></script>
</head>
<body>
<div id="phasor" style="width:400px;height:400px" />
<script>
// generate a waveform set from the source data; this can contain multiple
// series of waveform data that contain multiple cycles of wavefom samples.
var wfSet = ACWF.WaveformSet.create(sampleData);
// analyze a cycle of data starting at the specified sample
wfSet.analyze(0);
// initialize the phasor plot to display itself inside the element
// with id="phasor"
var phasor = new ACWF.PhasorDiagram("phasor");
// plot the waveform data
phasor.plotWaveformSet(wfSet, 0);
</script>
</body>
</html>
var dataFormat = {
title: "My Waveform",
samplesPerCycle: 32,
lineFrequency: 60,
// data is an array of waveform data objects
data: [
{
// Samples for one or more complete cycles.
samples: [0, 58.52, 114.80, 166.67, 212.13, 249.44, 277.16, ...],
label: "V1", // Label used to identify channel.
unit: "Voltage", // Unit is used to scale groups of similar waveforms.
phase: "1" // Phase is used to color waveforms.
},
{
samples: [300.00, 294.23, 277.16, 249.44, 212.13, 166.67, 114.80, ...],
label: "I1",
unit: "Current",
phase: "1"
}
]
};
Some of the plotting functions take an options argument. If no argument is provided these default values are used.
var acwfOptions = {
// Defines unit styles. These options are used to set line
// styles for units shown on the plots.
unitStyles: [
{ name: "Voltage", style: { width: 1, isDashed: false } },
{ name: "Current", style: { width: 1, isDashed: true } }
],
// Defines style variations for phases. Each phase is shown
// in a different color. These colors are "added" to the
// unit styles.
phaseStyles: [
{ name: "1", style: { color: "red" } },
{ name: "2", style: { color: "blue" } },
{ name: "3", style: { color: "green" } }
]
};
Phasors are represented by the ACWF.Phasor class. It has three properties:
- magnitude
- angle
- label
Note that the angle property is in radians.
Harmonics are represented by an array of two-dimensional arrays. The inner array contains the harmonic number as the first value and the harmonic RMS magnitude as the second value.
var harmonicData = [
[0, 0], // 0th harmonic = DC offset if any
[1, 26], // 1st harmonic = fundamental
[2, 0],
[3, 4]
];
Core classes for waveform representation and analysis.
-
ACWF.Waveform
Represents a waveform, exposing an array of samples and a label. Performs RMS and peak analysis on the waveform.
-
ACWF.WaveformAnalyzer
Performs a spectral analysis on a set of samples. Provides RMS, frequency spectrum, phasor, harmonics and THD.
-
ACWF.Phasor
As described above, represents a phasor for an AC waveform. Provides magnitude, phase angle in radians, and a label.
-
ACWF.WaveformSet
Contains one or more ACWF.Waveform objects. Manages scales for the various waveform units (i.e. voltage, current). Provides iterator methods for ease of access to waveform analysis results.
-
ACWF.PlotStyle
Waveforms in a set are often related, and when plotting waveform data it is helpful to use a consistent set of colors and line styles. The PlotStyle class represents the settings used to plot a specific waveform, but also allows altering the plot style to represent different but related waveforms. For example perhaps voltage waveforms are solid with a different color for each phase. The base line style can be defined and then a new plot style created that differs only by color.
Renders phasor plots using HTML5 canvas.
-
ACWF.PhasorCanvas
Draws a phasor diagram onto a canvas element. The constructor takes an id for a div that will be used to contain the canvas. This class only performs the drawing steps based on a data structure containing descriptions of the drawing elements that make up a phasor diagram. The data structure is generated by the ACWF.PhasorEngine class; both these classes must be used to produce a phasor diagram.
-
ACWF.PhasorEngine
Given a set of ACWF.Phasor objects, generates drawing instructions for use by ACWF.PhasorCanvas. This approach allows the phasor engine to be unit tested.
-
ACWF.PhasorDiagram
A facade class that provides a single class to generate a phasor diagram. Makes use of the ACWF.PhasorEngine and ACWF.PhasorCanvas classes to produce a phasor diagram. Most applications should simply use this class.
-
ACWF.WaveformCanvas
A rudimentary multi-channel waveform plotter. Used to visualize waveforms when a full-featured plotting library is not needed.
For those not familiar with AC systems the next couple of paragraphs attempt to provide a basic explanation for the layperson.
Ideally the AC signals are perfectly sinusoidal at the power system frequency; in reality this is often not the case. Nonlinear loads such as switch-mode power supplies and variable frequency drives draw distorted current waveforms. AC power sytems are designed and sized to operate at the power system frequency (also called the fundamental frequency). Different waveshapes can cause equipment overheating and misoperation. Harmonic analysis is used to measure the amount of "extra" signal present and how it might affect the power system.
A three-phase AC power system uses three sets of sinusoidal power waveforms separated 120 degrees from one another. The current and voltage wavefors generally differ by a small amount. Inspecting variations from this normal arrangement can tell you if the system is correctly wired or is in some other unusual state. This information is often represented by a phasor diagram in which the waveforms are represented by vectors or arrows. The length of the arrow shows the magnitude of the waveform and the angle between the arrows represents the phase shift between the waveforms.
Copyright (c) 2014 Jeffrey Yeo, released under the MIT license.