A three speed motor

Bonjour tout le monde!

some news: the final simulations with FEMM are almost completed. I now have a pretty good idea on how the motor will perform and will very soon be able to order my laminated steel ... 

How time passes and thanks

It has been over two years since I started working on the Quadrupole electric motor. I had a few people exchanging knowledge with me and also, giving me good advice. So, I would like to take this opportunity to thank each of them.

The non-obvious behaviour

During my first simulations way back then, I noticed that BackEMF in the inner and outer coils of the stators were not equal. This meant that the airgaps of the two stator were also "unballance". So I tried to eliminate it and led me nowhere. I abandoned that path because it was time consuming.

So my adventure continued without paying attention do this behaviour of the Quadrupole. In this situation, I was more interested to have the Back-EMF waveform to mimic the voltage sinusoidal wave source.

To recall; the main objective with the Quadrupole motor is to achieve high torque, high speed, and not use as much as possible torque weakening technique to achieve speed.

I discovered that by disconnecting for instant the outer coils from the simulation it gave more speed but lower torque, so a pseudo-field weakening technique without the controller/inverter being involve, simple logic. I have never pay any attention in my early simulations since I did not quiet understood the torque and counter electromotive force constants. It is not obvious for non-practitioners in this field of research, but the Quadrupole motor can act as a three speed electric transmission!

How is this possible? Just because the Quadrupole motor is radially design! The radius and the circumference length of each airgap are always unequal. The magnetic flux densities of the air gaps will therefore uneven. Comparing this to an axial flux motor having two stators, the axial flux in the airgaps of both stator are always equal. So, what was not obvious became clear and hit me!

Three values for the torque and back-EMF motor constants in one motor

Another interesting thing about the Quadrupole motor is that its torque and BEMF constant will vary according to wire phase configurations.

If the outer and the inner stator coils are configured to be connected in series, the torque constant of the latest design, is 0.375 Nm/A and its BEMF constant is 0.375 V/rad∙s^-1.

If only the outer stator coils are used, the torque constant will now be 0.205 Nm/A and its BEMF constant is 0.205 V/rad∙s^-1.

If only the inner stator coils are in use, the torque constant will now be 0.145 Nm/A and its BEMF constant is 0.145 V/rad∙s^-1.

So the higher value of the torque constant, the higher will the torque be. On the other hand, the lower the BEMF values will be, faster the rotating speed be.

Configuring the new winding schemes

By modifying and reconfiguring the wire connections of the inner and outer winding, it is possible to have a three speed electric transmission-motor that could give a sporty-like drive as if the vehicle was equip with manual 3 speed mechanical transmission.

At the date of the publication of this post, the results of the latest Quadrupole motor are described below.

1) At first speed for high torque at 37.5 Nm and low speed of 3700rpm: the coils of the inner and outer coils are connected in series. This means that the windings of phases 1, 2 and 3 with respect to coils A, B and C of the outer stator are connected to their sister the windings of phases U, V, and W of the inner stator respectively.

2) At second speed for medium toque of 20.5 Nm and speed of 6700rpm, only outer stators windings A, B and C are active.

3) At third speed for low torque of 14.5 Nm and high speed of 9500 rpm, only inner stator windings U, V and W are active.

The above figures are achieve with a 144 Vdc and 100A peak (71 Arms).

Now, how will all this be controlled?

Probably, the easiest way to control the speed and torque by is be re-configuring on the fly the wiring connections by using a motor contactor. High power SSR could be use but a minimum of three will be required for each phase. Motor contactor is probably the best way to go for testing. However, how the inverter/controller will react to a fast change is unpredicted and will certainly be a nice challenge,

Or again, two controllers might also be a good option. One controller per stator and each controller will see a single motor. Having them connected in parallel, it will raise the efficiency of the whole scheme at the expense of raising the current, since they will be connected in parallel from the point of view of the battery pack. The controller / inverter will have to be "disconnected" by changing the value of the analog input of the speed demand. For example, we have the controller / inverter A connected to the phases of the outer stator and controller / inverter B connected to the inner stator phases and a button or handle could be used for electrical shift applications. First, the two inverters are used for the first mechanical/electrical speed and the throttle is use to sens the analogue signal to both of the inverters. By manipulating the button or handle, we move to the second speed by sending an analog 0 volt signal to the inverter B at and inverter A will continue to receive its signal from the throttle. For the third speed analog entered the inverter A will subsequently be set to 0 volts and the inverter B now receives its analogue signal from the throttle.

Advantages

The biggest advantage is that directly coupling the motor to the transaxle drive system of the vehicle will ease the coupling to an electric motor. Also avoiding to the manual transmission will also reduce mechanical losses and reduce weight.

Is this great or what?

Why concentrated magnetic field?

Concentrated the magnetic field is not a new idea.In fact, Dr. T.A. Lipo has worked extensively with this principle by developing reluctance motors.The magnetic field was concentrated by installing the stator permanent magnets whose dipoles were repulsing. Mr. Flynn also use this principle to patent the technology of the magnetic path. Moreover, Mr. Flynn explained very well in one his papers the how and why (unfortunately, it has seem to have been removed from flynnresearch.net website).


In the Quadrupole motor/generator (and also other project like the LRK project on the openvolta website), I have been using the PMs (permanent magnets) in the same fashion as M. Flynn and Dr. Lipo however, in the rotor, not into the stator.

If we have 2 PMs having the same dipole facing each other, a repelling force is produce. However, if you put a block between each, it will concentrate the magnetic flux within this block and if the block in not saturated of magnetic flux, then the PMs will stick to the block. If close the loop, each blocks will have a single pole, they will emulate a homo-polare magnet.

The advantage of doing this is adding force. So if you have both magnet with a unit 1 force, adding them face to face with dipole alike, you'll get 2 forces of unit! Right?.. No! you will get 4 forces of units!

A bit of math!  

No, we are not going back to school but if we need to understand how we get 4 times more force, we have to know about one basic equation.

Note that the equation is valid only for cases in which the effect of fringing is negligible and the volume of the air gap is much smaller than that of the magnetized material (less then 5mm).

The mechanical force between two nearby magnetized surfaces can be calculated with the following equation.

F = μ₀ H² A / 2

where:
 F is the force, N (Newton),
A is the area of each surface, in m²,
H is their magnetizing field, in A/m,
μ₀ is the permeability of space, which equals 4π×10⁻⁷ T·m/A

Since we are dealing with magnets, it is easier to use the following equation:  

F = B² A / 2μ₀
where:
B the flux density, in T (Tesla).

An easier way to express this is: F = 400 000 B² A.

Proof of concept:

As show here, the magnet is on the left side inserted in the 2 parts to create the core and the attracted armature on the right side. The airgap is 1 mm.

One part core is 40 mm x 100m x 20mm depth. The total area A = 40mm x 20mm x 2 poles= 1 600 mm². The area has a flux density of approximately 0.4 T.

F = 4 000 000 ­x 0.4²x 0.001 6 = 102.4 N
If we verify with FEMM (finite element method software), the computed value is 108.1 N, which it is normal since the exact flux density is 0.411856 T.

If 2 PMs are put in parallel has shown here, we can see that the field density in the core and the armature has increased. If we use the same equation, one would think that since we have 2 PMs, we just have to multiply by 2 the force where 2 x 115 N = 203N. This not correct.

Since we have 2 PMs which faces the same dipole, the equation should therefore be restated to reflect this physical aspect. Therefore,  F = 400 000 x (2B)² x A. So the true value of this attracting force will now be F =  400 000 x (2 x  0.4)² x 0.001 6 = 409.6 N. So, 409.6 N / 102.4 N gives up to 4 time the initial force!

The magic is here, since we do have 2 PMs, we have two times the flux density (T);  2 x 0.4 = 0.8 T. Then the square root of 0.8 is 0.64 T. So basically what we are doing here if we assume that on magnet as 1 unit of force (1force x 2) x (1force x 2), we can now see that we quadrupled the force if we look only the components "2".

The results with FEMM yields to 431.6 N. Again 431.6 N / 108.1 N = 3.992 N, rounds up to 4 time more force.

The Quadrature

The quadrature is basically an arrangement of magnet that focuses the magnetic field in the centre of the quadrature. This is also know as a quadrupole magnet. This basic idea is use from which it inspired to design the rotor

 

The rotor

The Quadrupole motor / generator utilizes the PMs in parallel the quadrature, like the quadrature magnet technique to concentrate the magnetic flux within segment. When looping the segments with a PMs, the active production of torque is 4 time higher than using magnet only.

Also, putting 2 stators, in inside, the outer, outside, we will radially that full advantage of the rotor, not just in or out of the rotor. This is like having 2 motors / generators in one machine.

The yoke of the rotor and a simulation with FEMM

Here's an other model of the Quadrupole motor.

In this picture, I have design the yoke to attach to the rotor assembly. Just need to add the coils and hardware to finish the job.

Below, here is movie of the FEMM simulation that was perform last October.

The simulation shows the flux orientation of the segmented rotor going in and outward to the stators.

Modeling the 3D motor.

Finally, here's a start of a 3D model of the Quadrupole motor project.

 

http://openvolta.org/files/Quadripole/quadrupole1.pdf

Welcome the OpenVolta Blog - my first post!

On this blog, I will publish my own designs of electric motors and generators as part of the OpenVolta project. The results will be published as well as CAD drawings. 

So everything you see here is open source, open motor, open generator... An open technological blog. My way to share to you might work that will hopefully be helpfull to anyone that would like to built their open electric motor or generator.

Why not patent my work? I could and I might... One day I supposed. The real reason is that I don't have time to go through the hassle of patenting a project and spending hundreds or even thousands of dollars, in patent and then to protect it. So why not share. I'm no genius and just hope that what I propose will serve someone purposes. If I achieve this, then thank you to myself.

Time is running out. We need to unite our forces together and start cooperating, globally, to make this world better. Nice cliche will you say! Yes but again, it's true.

If you would like to have a bit more information about the work that I have done, I invite you to visit the openvolta website for the time being until more information about my developments are published.

What I can tell you is that I'm focusing much of my efforts on the Quadrupole motor/generator. This a new motor design. As you can see below, the structure of the Quadrupole motor/generator is a single rotor having a quadrature magnetic field, sixteen in total and a dual stator (inner and outer). This type of rotating machine as the rotor set between two stators and the flux is radially distributed inward and outward of the segments of the rotor. The rotor’s topology has an arrangement of permanent magnets (PM) installed circumstantially and tangentially to the segments so that the PMs are such that the adjacent pole have the same identical polarity to concentrated the flux within the segments. The segment retains most of the flux.

 

 

This rotating machine is 280mm diameter and only 38mm depth and at 100 amps, it will output up to 35 Nm and 18kW at 144Vdc.

I have also publish a paper. It is available at the openvolta website.