This thread is meant for discussions on simulations regarding the RomeroUK motor / generator.
Please use this thread to share your understanding and discuss disagreements with patience and politeness.
My purpose is to build up knowledge by sharing and converge insights.
As for myself I will share my 'virtual replication' using Ansys Maxwell.
My simulations are done in 3D.
An overview of my own model pictures are attached below.
I copied as much details as possible as shared by RomeroUK, so yes even the washers are in, as well as the ferrite cores.
I will do modelling request on rare occasions, since this will take a lot of time, Maxwell needs several hours to calculate a singe simulation of one complete rotation revolution.
Please, do not ask for the source files, as I will not make them available for open sourcing.
If this one appears to be successful and you need commercial design consultancy, drop me a PM or e-mail.
Next, I will start sharing simulation results of the basic generator principles that I simulated first to build up knowledge.
Enjoy this discussion thread!
Teslaalset.
Attached the outline of the model I used for building up basic understanding of the generator coil principle.
There's a fixed magnet positioned above a coil with a ferrite core and a moving magnet beneath it.
The movement is along and within the transparent square bar of the picture.
I generated a nice flux vector simulation represented in an animated GIF file, the file can be downloaded from here:
http://www.multiupload.com/9ZG6AGYPL1
The circuit that is connected to the coil is depicted below.
It's basically a diode bridge and a big capacitor with a parallel load resistor of 100 ohms
Next step, I will show some force graphs of three simulations I ran with different distances of the stationary bias magnet.
Some graphs on magnet forces in the direction of the movement of the single coil model.
I varied the distance of the bias magnet by 0.05 and 0.1 cm after starting at position 0.
Position zero is already a rough optimum.
The first three graphs below show the force as function of time.
The total run is 9 ms, where 4.5 ms is where the moving magnet is at TDC, so just centrered below the coil/core.
The graphs are somewhat noisy due to the mesh size of the model.
Mesh size determines the accuracy of the model.
Very fine mesh size will result in perfect graphs, but it will take endless amount of calculation time.
So, I took a mesh size that shows the trend but also gave me acceptable simulation times.
Target is to have the average force over time around zero Newton so effectively no nett negative force (drag) is generated by BEMF when a magnet passes by a coil/core.
You'll notice that two experiments show such results, the third result is mainly resulting into negative values, causing unwanted drag.
To give a more accurate determination, I have integrated those three graphs over time.
This is the fourth graph. You need to look at the end value of the integrated curves. If the end result is zero, the bias allignment is perfect (red line).
The green line clearly shows negative integral force, this will cause BEMF drag and slow down the rotor.
Last graph is the voltage over the load capacitor.
The simulation starts with a bias voltage of 20 volt on the capacitor as a starting point.
You will notice three time phases:
- the start period, where mainly discharge of the capacitor is happening due to the 100 ohms in series
- the load period, where inducted flux charges the capacitor, superseding the discharge by the 100 ohms.
- the last period, where discharge is happening again due to lack of induced flux.
The three graphs represent the various bias offset again of the stator magnets.
So, not only influences the bias distance of the stator magnet the BEMF forces, it also influences the charge capability of the setup.
In this example, you'll notice that the capacitor will discharge in all three occasions, so no power left to drive the motor coils.
By decreasing the distance between the moving magnet and the ferrite core, induced flux can be increased so the result will give a higher end voltage at the end of the total simulation period.
In this particular run, when the offset of the capacitor at the start of the run is chosen at a lower value, say 10 Volt, the same run will show surplus of the capacitor voltage at the end of the same simulation run.
Thanks for you help and explanation of this. Good to know BEMF is one of the key components in the OU generation.
Is the Ansys Maxwell program a standalone program or just a component of a larger package needed to do these sims?
Quote from: e2matrix on June 06, 2011, 03:36:07 PM
Thanks for you help and explanation of this. Good to know BEMF is one of the key components in the OU generation.
Is the Ansys Maxwell program a standalone program or just a component of a larger package needed to do these sims?
Ansys Maxwell is a stand alone program that can be linked to other simulation software of Ansys (so, its compatible with those).
Keep in mind Maxwell is extremely expensive, around 50k$.
It's the best 3D software available for these kind of simulation in my view.
Most of the high tech mechatronics companies use it for professional modeling.
Quote from: teslaalset on June 06, 2011, 03:39:29 PM
Ansys Maxwell is a stand alone program that can be linked to other simulation software of Ansys (so, its compatible with those).
Keep in mind Maxwell is extremely expensive, around 50k$.
It's the best 3D software available for these kind of simulation in my view.
Most of the high tech mechatronics companies use it for professional modeling.
well done teslaalset
this is the kind of RND the OU motors need to establish operation parameters. thank you
I will be recording any data you present.
please keep us informed and break it down into Lay persons speak so we can all get our heads around this.
Quote from: toranarod on June 06, 2011, 05:10:28 PM
well done teslaalset
this is the kind of RND the OU motors need to establish operation parameters. thank you
I will be recording any data you present.
please keep us informed and break it down into Lay persons speak so we can all get our heads around this.
You're welcome.
As I am a rather distorted EE (;)), I may be going too fast with my explanations for some of the readers here.
If you need deeper explanations, let me know, I'll try to simplify my findings into the desired layman level.
Teslaalset,
I second toranarod. Many thanks for providing the "charts and graphs" of data. This is what I, and possibly many others, have been waiting for (second best to another self-runner). Maybe it is the engineer in me...
Replicators, don't get me wrong. I am also very appreciative of all your hard work. I have even tried to get something(s) together to do some testing. But my goal was not to replicate, but instead to investigate first. And then "design" something to harness the OU effect. So that would require testing and data collection while making measurable and tiny adjustments of parameters (dimensions, rpm, etc.). I thank you for providing your input, but they have been single data points (and more than I've accomplished). Teslaalset has shown how small the window is for finding this effect. No wonder no one had stumbled upon it with their replications yet! But now we have a finding that may allow you to design a device with the correct parameters.
Teslaalset, please continue. Any and all data that you can share is greatly appreciated.
M.
@teslaalset
great simulations !
Well, could you also show a real 3D view of the flux lines inside the whole
motor when the rotor turns or does this animation take too long to calculate ?
Maybe just do single frames and then do an AVI encoding
of all the frames by a BMP to AVI (XVID codec) encoding program or
just import the single frames into Microsoft Moviemaker
and encode them to WMV or something like this.
I would really love to see a spinning rotor and see all the flux fields in 3D view.
Can you also change the camera position over time, so you can make a roundview
trip around the motor ?
Or does Maxell only show the flux field with these vector arrows ?
This would be too bad, as it is not so good in my opinion and hard to see
then...
Also your GIF animation example was only a 2 D side view and not a real 3D view I guess ?
Would be interesting to see the real inner flux field of the ferrite core in 3D.
Many thanks again.
Regards, Stefan.
Quote from: hartiberlin on June 06, 2011, 08:28:05 PM
Well, could you also show a real 3D view of the flux lines inside the whole
motor when the rotor turns or does this animation take too long to calculate ?
I'll see what I can generate this week. I don't expect much of a difference to show the flux in the ferrite of the whole rig compared to the single module I showed in my first posting.
Quote
Maybe just do single frames and then do an AVI encoding
of all the frames by a BMP to AVI (XVID codec) encoding program or
just import the single frames into Microsoft Moviemaker
and encode them to WMV or something like this.
I can generate AVI files too, but they are much larger than the animated GIF.
I will post an AVI later this week.
Quote
I would really love to see a spinning rotor and see all the flux fields in 3D view.
Can you also change the camera position over time, so you can make a roundview
trip around the motor ?
Round trip is simple, this only requires 22.5 degrees of simulaton and then loop it.
I'll post it.
Quote
Or does Maxell only show the flux field with these vector arrows ?
This would be too bad, as it is not so good in my opinion and hard to see
then...
There are 3 types of vectors possible, but also just coloring grading the investigated element.
Quote
Also your GIF animation example was only a 2 D side view and not a real 3D view I guess ?
Would be interesting to see the real inner flux field of the ferrite core in 3D.
The simulation was done in 3D, but I showed 2D view because in my opinion this was the most clear view. I'll post one in 3D, so you can see the difference.
[quote author=teslaalset link=topic=10841.msg289888#msg289888 date=1307431511
I can generate AVI files too, but they are much larger than the animated GIF.
I will post an AVI later this week.
Round trip is simple, this only requires 22.5 degrees of simulaton and then loop it.
I'll post it.
[/quote]
22.5 = 360/8/2 larger than 20 = 360/9/2 , this mean that you find symmetric effect in the coil? there is no type of hysteresis
Quote from: wings on June 07, 2011, 04:55:38 AM
22.5 = 360/8/2 larger than 20 = 360/9/2 , this mean that you find symmetric effect in the coil? there is no type of hysteresis
You are partly right, Wings.
It depends on what coil you watch the details.
If I zoom into a coil where the rotor magnet position is started 11.25 degrees before the intended stator coil and then simulate a rotation stroke of 22.5 degrees, it will give sufficient info to represent reproducable fllux variations.
Quote from: teslaalset on June 07, 2011, 05:07:49 AM
You are partly right, Wings.
It depends on what coil you watch the details.
If I zoom into a coil where the rotor magnet position is started 11.25 degrees before the intended stator coil and then simulate a rotation stroke of 22.5 degrees, it will give sufficient info to represent reproducible flux variations.
I see ... the hysteresis of B-H curves
interesting;
the simulation can be useful to see the electromagnetic interaction, how you can see the electronic part like current, voltage with high capacitance?
@ teslaalset
I'm studying your model and the results, as we speak, and I'll comment more intelligently shortly, but thank you for doing these simulations and models, they look great!.
EM
PS. Ok, here's some questions teslaalset,
How do you derive the force that you plot? Do you first use the calculator inside Maxwell to sum up the surface forces vectoraly, and then take this resultant vector and do a dot product with a unit vector in the direction of the motion? this is how it should be done from what I remember.
also, it would be nice to produce a smoother force profile, and I would expect it from the software as this is a very simple model. So I'm wondering how you actualy modeled the coil? And I mean the coil not the ferrite core?
And most importantly, make sure you use the SAME mesh for all the 3 different scenarios, and use a highest fidelity mesh generated with the closest gap and the magnet at TDC, and make sure you tell the mesher to use symetry, as the mesh will not always be symetric just because your model is symetric. Symetry of the mesh, about the TDC line, is very important in this setup as we are trying to look for an inbalance in the forces.
Anyway, give those comments some thought. Good work!
Quote from: wings on June 07, 2011, 10:12:39 AM
I see ... the hysteresis of B-H curves
interesting;
the simulation can be useful to see the electromagnetic interaction, how you can see the electronic part like current, voltage with high capacitance?
@Wings,
I am not sure I understand your remark on B-H curves.
What I see is that in the example of a single coil / two magnets the magnet passes by, starting from left, to TDC, then to right, so currents in the coil will make a positive and negative swing.
Regarding the electrical part, Maxwell can inmport electrical circuits. In this case a simple one that romeroUK uses, kind of. Currents and voltages can be monitored by placing meters in the circuit, like I did in the above example.
Quote from: EMdevices on June 07, 2011, 07:17:22 PM
@ teslaalset
I'm studying your model and the results, as we speak, and I'll comment more intelligently shortly, but thank you for doing these simulations and models, they look great!.
EM
PS. Ok, here's some questions teslaalset,
How do you derive the force that you plot? Do you first use the calculator inside Maxwell to sum up the surface forces vectoraly, and then take this resultant vector and do a dot product with a unit vector in the direction of the motion? this is how it should be done from what I remember.
also, it would be nice to produce a smoother force profile, and I would expect it from the software as this is a very simple model. So I'm wondering how you actualy modeled the coil? And I mean the coil not the ferrite core?
And most importantly, make sure you use the SAME mesh for all the 3 different scenarios, and use a highest fidelity mesh generated with the closest gap and the magnet at TDC, and make sure you tell the mesher to use symetry, as the mesh will not always be symetric just because your model is symetric. Symetry of the mesh, about the TDC line, is very important in this setup as we are trying to look for an inbalance in the forces.
Anyway, give those comments some thought. Good work!
@EMdevices,
Good to see some OU veterans having a look at my attempts here.
Forces: I can set up a torque or force measurement while selecting one or more component in the model. In this case I selected the moving magnet for calculating the force on it.
I am not sure how Maxwell processes its internal data for it. It's made available via the GUI of the program as an output parameter (I use Maxwell V14, the latest version of Ansys).
As for defining the coil, this is done via defining the physical area and define a winding + terminal, while also defining single or multi strand. So, even RomeroUKs 7 strand Litze can be used.
I agree that the force output is quite noisy, but like I mentioned, I chose a rather rough mesh to have an acceptable calculation throughput time.
Finer mesh is ending up in a 'night batch', since it will take several hours ;).
It's not my PC's capabilities, I just assembled a number crusher out of an I7 Intel processor, 16GB of RAM and a SATA 600 SSD.
I used identical meshes for all three force runs.
To allow for fine local meshing I put 'airboxes' around the magnets so the mesh around the magnets have more details locally.
I have to look into symmetrical mesh, that is a good tip and makes sense.
Thanks for helping out here, there are not many FEM specialists around at OU.
What FEM software do you normally use?
Some of the things I have on the agenda for simulation is the determination of the delayed BEMF forces.
To explain a bit more, look at the attached graph (just a drawing, no simulation).
Negative vertical axis represent counter force towards the rotational direction, positive vertical values represent pushing (driving) forces in the direction of the movement.
- the blue line represents the force on the magnet without any electrical load to the stator coil while that magnet is passing by a stator coil/core combination. Zero on the timescale is TDC (top dead centre). First the rotor magnet will be attracted to the ferrite core, once it passes the core, it will be attracted in the counter wise direction.
So, attraction in the direction of the motion is has a positive force value, attraction in opposite the direction of motion is negative. Without taking losses into account, the sum (integral) of the forces will be zero in such situation
- The red line represents force caused by non delayed BEMF when a load is connected to the coil. All the time the forces caused by BEMF work as negative force against the direction of motion.
- The grant total of a loaded coil setup is represented by the green line. The integral of this grant total is negative.
So, what I am planning to do is finding out what the delayed BEMF force curve looks like when the bias magnets are in optimum position (sum of all forces are zero over the complete stroke), so we know how the delayed BEMF force curve really looks like.
That will help in understanding the BEMF current in the generator coils, and also the flux behaviour in the core.
This is done via indirect simulation. First I plan to determine the 'blue curve' , so no load.
Then I do the loaded coil simulation again, like the second force graph in my posting #2 of this thread (stator bias magnet position at 0.05). That will give me the sum force graph like the green one in below graph.
Then subtract those two results and the delayed BEMF force curve will be the result (the red graph in below picture).
My expected result will be quite different from the red curve as shown below.
Maybe this is more complicated than that, since the core will also change it's mechanical attraction due to (time and location dependant) saturation. We'll see.....
For the guys in the experimenters thread some graphs of the generator coil signals.
First graph indicates the currents induced in all 9 coils time wise
Second graph indicates the flux induced in all 9 coils time wise
Third graph indicates the induced voltages in all 9 coils time wise
Fourth graph has all 3 signal for only coil nr 1 represented
Some flux animations within two opposite cores in the complete model.
The AVI videos can be downloaded here:
Vectored version:
http://www.multiupload.com/WEQJNJ7XYM
Cloud version:
http://www.multiupload.com/O72CBIMJN2
The videos are probably best to be viewed in looped mode.
Below a snapshot from vector version video: