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?
