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[split] EEG EM Basic Circuits
One Proceedure that may be used to Determine Some Initial Design Objectives

The following proceedure might be one method to use in determining a usable mixture of
design objectives between the pole material, pole windings, current and voltage. This is
static only, however a feel for a starting point may be gained. AEDT Student can be used. 


Attached Files
.pdf   TFG_Z01_TRa_Magnetostatic_Design.pdf (Size: 507.6 KB / Downloads: 18)
The following post attempts to answer some questions found in a few of
the Forum threads.

Windings - Inductance - Resistance

Precision Microdrives (Technical Resources) AB-022
[Reference Information - PWM Frequency For Linear Motion Control]

Keep in mind we are not concerned with motor control; however we just want to keep the
current in our coils "moving," therefore the goal is not maximum torque, etc.. Just keep the
current "moving" in the coils and only use as much current as we need to achieve ~ 1 Tesla
in the Pole structures. A non-linear current slope is perfectly acceptable.


- Input voltage is equal to the sum of the voltage drop across the inductor and the
voltage drop across the resistor [ VL(t) - Ve - tRLVR(t) = V(1-e-tRL) ]. VL moves toward 0 over
time and VR moves towards +V; until about 5 Tau. See the chart. Note that 1 Tau or 2 Tau
achieves the greatest slope of idt/t or vdt/t. This is good and wastes less.

See the charts for 50% at 2 Tau (4 tau) versus 50% at 1 Tau (2 Tau).

- Have a look at the Calculations paragraph, (in this case it's for a DC motor but still

- Note the Motor Current vs PWM duty curve for 31.5 kHz, 2kHz and 200Hz. But keep
in mind we are not that interested in linear behavour, plus we will likely use a 50% wave.

Motor inertia, etc. are not a part of our equation. Neither is the linear/non-linear
response, or vibration, and so forth. We just need the "Current to Slope."
  " di/dt "

Finding the Balance will be, in the end, part of the physical analysis and test.


Two Windings Versus A Single Winding for the Pole Structure

Several thoughts:

Performance Monitoring (BITE) and Operation

- First, consider the "Lamination Cut Pattern" lends itself to minimal waste. See the
previous diagram for details. The result was having "one leg" longer than "the other
leg." This also provides a degree of versatility, both functional and during design.

- It can also serve as a System "BITE" (Built In Test Equipment) scheme. Periodically
look at each Pole Coil as an insitu test {BITE} for nominal performance. This can
further test the System Performance.

- The "Loop Coil" will also pass information to the "BITE" Coil. Valuable during both
design development as well as operationally. The more status LEDs/Indicators, the
better. Might be very handy to internally monitor the system during the design phase.

- Redundancy, that is, if one Coil Leg should fail the second Coil Leg will still function,
all be it at a reduced performance, but your still not "dead in the water." Half power
is better than no power!

Design and Development

- During development one coil can serve as a "Test Port," that is, one coil Leg is driven
while the other Leg is monitored. This might provide insitu measurements without
requiring other additional modifications; simply a quick, wire re-arrangement.

- This scheme allows testing and measuring "series" and "parallel" coil configurations,
timing schemes, amongst other things that might be of interest, without modification.

- The design itself allows easily adding or removing Leg Coils as required - "slide on,
slide off!" Power both, power one, alternate, etc. Check the temperature rise, and so

Hope this answers your question, at least to some extent.


The Target Design is a "Stand Alone Device"

EE_TFG is meant to be an independant unit. The intent is to serve many applications
including a Battery Booster, enhance a Solar Panel output, and so forth.

Also, with the proper internal loop-back it may even provide a "stand alone" function.

This means it can be tied to an external AC supply feed to form an additional power
source but that's not a requirement. It would be one of the applications however.


The Resistor in Series with the Coils

The resistor is explained in some of the attached literature but it's primarily a design
function - a varialbe, so to speak, that sets the coil current for further analysis.
(02-07-2024, 04:56 PM)lfarrand Wrote: I believe you're referring to inductive reactance. It has to be considered when building such a machine.

If you are aiming for relatively high frequency then I think you need to try to minimise inductance, otherwise you will not be able to pass a large current through the coil.

If you are aiming for a low to modest frequency then you can of course aim to maximise inductance.

The above applies if you are aiming to pass a large current through a coil, however if you are trying to minimise the current from the source then I think it's best to aim for as high an inductance as possible.

Isn't it possible to use a series capacitor to "correct" the inductance? As explained in this article. It works best at the resonant frequency though.

It may be impractical for development as if we want to do a frequency sweep and find the best frequency for the given configuration, we would have to change the capacitance too. But that is probably better simulated first anyway.

I made the exact copy of the experiment I would like to try using the CAE (     ) and I am trying to figure out the best parameters, coil turns, frequency, what impedance will the coils have at which frequency and what resistance they will have at how many turns of wire. And the impedance really is quite limiting.
Just thought it might be instructive to further clarify a DC Pulse versus AC

RL Circuits - DC Pulse versus AC Source 

NOTE - The Differences Between DC and AC

WTCC ELC 131 All Videos (Video pages link)

ELC131 Inductors with DC and Pulse Sources

As opposed to AC

ELC131 Series RL Circuits [Impedance is the OPPOSITION to ALTERNATING CURRENT (AC)]

ELC131 Parallel RL Circuits [Impedance is the OPPOSITION to ALTERNATING CURRENT (AC)]


ELC131 Magnetic Materials

ELC131 Losses in Electromagnetic Systems
[Again - Note: The differences between DC and AC]

Also, consider "Retentivity" - when a "Pulse" reverses it's polarity!

ELC131 Electromagnetism

Hope the above brings-to-light the differences between DC (Pulses) and AC.

There are a number of other easy to follow, interesting, videos as well. 

Hi solarlab,

what signal do you use to excite the coils of the TF_EEG? Most often I use a 1kHz square wave that is alternating between 1 and -1 multiplied by some coefficient (like 12 if I am using it as 12V voltage source, or 0.1, if I am using is as current source of 0.1 mA). Actually I moved to an equation like this: 12*(sgn(sin(2*pi*time*_freq))), which produces a 12 V square wave and I can change the _freq to change frequency and I can also set the analysis parameters according to that (to show 2 periods with 10 sample points per period).

When trying to use this excitation signal for excite the coils, it will surely behave differently to powering a DC motor.

But maybe I misunderstood and it should have been a different kind of excitation signal.

Attached Files Thumbnail(s)
Hi Kloakez,

A "Dataset" is entered into the 'Excitations -> Add Winding' in either "Voltage or Current"
data area. Enter the "Name of the Dataset" you created in the "Edit Dataset."

A minimum entry would be, for example, "pwl_periodic(yournameddataset, time)".

You can add any variety of mathematical expressions if want an exotic waveform but the
minimum entry will do just fine. I think the dataset csv's are stored in a seperate folder,
they are just text files of the X-Y cordinates you entered.

This Dataset is defined in the Maxwell 3D -> Design Datasets dialog window. As you
enter the X - Y coordinates, a graphical display is shown for the entered data.

During the course of development I've probably created and tried a few hundred
datasets. Not that convienient to switch between them in the "Windings" dialog
but if you name them with some readable scheme (e.g. 5ms_SQW; 10ms_SQW)
you can just change the 5 to 10, and so forth.

Not sure where your Voltage equation came from but something as simple as
[12*pwl_periodic(nameofyourdataset, Time] should work for an input signal.
The 'pwl_periodic' will repeat your 'nameofyourdetaset' with an amplitude
of 12Volts [12*].

Cycles (# of Periods) and number of sample points are function of the "Setup."

Try a few things to get the feel for AEDT and how it works with excitations.

Sorry if I can't provide more specific help - but ADET is far to complex to go
through function by function in detail - the beginner course runs 6 to 12+ weeks
minimum just to learn the basics and that's not our goal here. However, there are a 
few good videos available.

Anyway, don't get too "wrapped-around-the-axel" with detailed timing at this
point since there are no "good scenarios" identified yet - still a work-in-progress!

Just calculate your "WAG" as best you can and go with it initially; then tweek it
in AEDT as required.


BTW -- "pwl' I think, stands for "piece-wise linear"

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