Chorus Simulator


Chorus Motors Stator Harmonic Current Simulator


Watch the simulator in your web browser
( Requires Java )

Download the simulator as an executable
( 170Kb EXE file; Windows version only at this time.   )

This simulator provides a graphic representation of the currents flowing in the model motor stator slots.   On the left are graphs of the current versus time for both the main drive current and for two selected harmonic currents, in each of the independent stator slots.   In the upper right is an animated simulation of the stator currents, with the magnitude of the current flow represented by dot size, and the sign of the current flow represented by dot color.   Both the main drive current and a selected harmonic current are represented, allowing one to see the rotating fields produced by each.   In the lower right are the simulation parameters.

To simulate an ordinary three phase machine, set the number of phases to 3, select 'spanned windings', set the speed to 1 and the amplitude to 35.   Additionally set the harmonic values to 5 and 7, and select the radio button next to harmonic 5.   Then click the play arrow button.

You will see three graphs on the left hand side.   These represent the slot currents for the main drive current, as well as for the fifth and seventh harmonic.   In the upper right you will see two rings of dots.   The inner ring is the main drive current, and you will notice that it is rotating slowly in a counterclockwise direction.   The outer ring is the selected harmonic, in this case the fifth.   You will notice that it is rotating much more rapidly in a clockwise direction.   This demonstrates how the fifth harmonic will act in a conventional three phase machine.

After clicking the stop button, change the number of phases to 18.   Click the start button is clicked to see a simulation of the Chorus® motor.   You will note that on the left hand side there are many more lines in each window, showing the increased phase count.   In the animation window, you will again see two rings of dots.   The inner ring is the main drive current, again rotating slowly in the counterclockwise direction.   The outer ring animates the selected harmonic.   You will note that in the Chorus® case, the outer ring changes rapidly from red to blue, and if you count around the ring you will see 10 separate red or blue areas, in contrast to the 2 separate red or blue areas of the inner ring.   You will also note that the outer ring is rotating slowly in the counterclockwise direction, in lock-step with the main drive current.

The meaning of the 10 separate red or blue areas is that the fifth harmonic produces a rotating current structure with 10 poles, even as the main drive current is producing a rotating current structure with only 2 poles.   This fifth harmonic 'rotating field' is synchronized to the main drive field, and will produce useful torque in a Chorus® motor.   Similarly, the seventh harmonic will produce a rotating field with 14 poles, synchronized to the main drive field.   In fact, all harmonics up to the phase count will produce synchronized rotating fields.   (Please note, if you simulate a harmonic count greater than 1/2 of the phase count, then the alternation of the dot sizes representing current magnitude will lead to the illusion of non-synchronized rotation.   Just follow a single red or blue dot as it works its way around the circle, and you will see that these harmonics are still synchronized.)

With this very simple simulator, the basic effects of harmonics on both three phase machines and upon Chorus® may be examined.   This simulation does not deal with aspects of machine design such as winding distribution or chording, nor does it deal with the magnetic flux patterns produced by the current flows.   Saturation effects are not simulated, and the relative magnitude of the harmonics is greatly exaggerated in order to render them easier to see.   We hope that this simulation helps in developing an understanding of the operation of the Chorus® motor.


 
 
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