Looking at a recent Automobile magazine article about electric cars from the automobilemag site (PM for details)
and the beginning comments "As it stands today, battery electric vehicles (BEVs) are little more than loss-making goodwill devices" and at the end "Research tells us that in 15 years time, 65% of the car-buying population will consider a BEV. Today that number is below 5 percent."
Given growth like that, it seems logical that alternatives to the current electric motors will receive strong consideration because, as that article states near the end, "EVA2 models will be no more expensive than comparable gas or diesel models."
Considering that Switched Reluctance Motor/Generator (SRMG) are powered by DC, generate DC and that batteries can only be charged with DC, the incentives for using SRMGs seem to be enough to invest in the development of SRMG based automotive drive-trains, especially as a means of reducing both weight and cost.
The design of the Switched Reluctance based drive-train depicted in the attached illustrations are available for use by anyone to use (PM for details) Very much like Open Source in software. My expectation is for others to build on this design and share their additions, including a suitable circuit design, with others, as I am willing to elaborate to the best of my ability on the design details. Tesla, Toyota and others have already made their patent portfolios available to others and this design is offered in a similar vein.
Electric Vehicles (EVs) have gained their popularity mostly because of their positive environmental impact. However, in a 90 million unit vehicle annual world market, the environment can be helped only when EVs gain a substantial percentage of that market. If that is to happen, they need to be more in the price range of the Chevy Spark and similar vehicles that can be bought for under $15,000 (in Mansfield Ohio for under $11k) or the Ford Ka, my original target for this design.
This Creative Commons submission is a way of helping anyone, wanting to help that environmental goal, build on this submission.
Pictured in the attached illustration #1 is the Switched Reluctance Motor/Generator (SRMG) in RED on top of the differential, just for mentally illustrating, the rear of a Ford Escape Four-Wheel Drive or similar, turned vertical, rather than horizontal, as they are normally deployed, and without the viscous clutch.
1. An SRMG is powered by DC, generates DC in its regenerative charging mode and, of course, batteries can only be charged with DC.
2. A SRMG does not require an inverter and, because of 48 Volt automotive technology being heavily pursued, DC to DC and intelligent charging could reduce the cost of the overall BEV drive-train. Intelligent charging in this case means that electricity "drips" from the generator to an electronic accumulator of sorts, perhaps a capacitor, that "flips" a "unit" of the accumulated power into the battery at whatever "flip" it is set for.
3. A pancake configuration is more torqy
4. You can see in illustration #2 the rotor and stator are modular, typically magnetic steel based, components that are captured in aluminium castings.
5. This design allows both the motor and the generator to be engaged in phases so that employing one of the, for example, four phases produces minimal torque or braking while deploying all, for example, four phases produces maximums. Those phases need to be balanced, of course.
6. SRMG's do not use environmentally problematic rare earth materials.
7. Using aluminium to "stretch" the poles reduces the overall weight.
8. The aluminium reduces the undesirable reluctance interference to the adjoining poles.
9. The aluminium castings allow more effective cooling channels than totally steel would, and those channels will become part of the climate control system.
10. The pancake configuration sits directly on top of the pinion shaft to the ring-gear eliminating the typical EV 90 degree gearing from the motor to the differential. Gearing could be inserted there, if desirable.
11. Torque vectoring clutches, preferably based on intermittent electro-magnetic slipping, rather than constant electromagnetic activation that takes more current, could be used instead of a differential.
12. The pancake configuration on top of the differential allows the SRMG to be bolted to the differential through the bottom of the enclosed compartment that holds the SRMG and controller thus physically separated from the rest of the drive-train.
13. That compartment will be clean and out of the mud capturing additional heat for climate control purposes, rather than wasting that energy to the atmosphere. Cooling can, of course, be done with a, preferably scroll compressor based, heat-pump like made by Copeland Division of Emerson in Sydney Ohio.
16. Image #3 attached is an illustration of a standard Switched reluctance device where the poles face each other, rather than where the rotor poles run through u-shaped stator poles that have the coils inside the bottom of the U as shown in RED in the animation, image #4 - in email #2
15. The Regenerative Braking
function of an SRMG driven electric vehicle is, of course, identical to the generator function of the witched Reluctance Generator (SRG) in a wind-turbine.
Therein lies the rest of the story. How Henry Keultjes pursuing development of a wind-turbine came upon this EV drive-train.
A write-up about rationale of the EVs and the ability of car companies to exploit the very same manufacturing technologies like stamping, die casting and even electronics can be readied in a day or two.
Henry Keultjes will be glad to share further details under the same Creative Commons license through DIYElectric Car or <firstname.lastname@example.org>
Mansfield Ohio USA