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Old 03-06-2012, 12:24 PM   #5 (permalink)
Ken Fry
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Quote:
Originally Posted by Ryland View Post
Anyone care to pick it apart or steel the idea and build it?
I stole the idea and built it! My POC prototype uses a couple of very similar PM motors.

The Perm motor has a speed constant of about 45 rpm/v, so at 96 volts goes about 4500 rpm. I doubt that they are able to stay together at 12,000 rpm. That would also equate to 266 volts -- far above the motor's maximum voltage rating, I'd think. I'd evaluated the Perm for my POC (and subsequent production) and it is a great motor, but brushed (a maintenance and RMI issue) and not quite the right voltage constant for my project. The Perm people (in Germany) are straight shooters and helpful, so if you want to pursue this, contact them.

My POC is 540 lb, and a motor of this size works fairly well -- albeit only with a multi-speed gearbox. (With a single reduction, getting a useful top speed means a reduction that does not yield enough wheel torque for good hill climbing.)

(Series motors and AC induction motors are a little better in this regard, but not perfect. Tesla's original idea of using a two speed box was appropriate, even with their AC induction motor. You cannot claim that 120 mph top speed is "supercar" performance: it's less than the top speed of my 2010 Honda Civic. So they went for acceleration alone, (at which it is excellent). The Tesla's peak HP would allow it to go faster than the Lotus equivalent, if it had a two-speed box. )

Quote:
but as I understand it, you can program how fast things like regen ramp up and how strong, if possible it seems like two regen settings would be ideal, one for when engine vacuum is high and another for when the brake lights come on,
Yes, this stuff is very easy to implement with a PM motor. You can have any amount of regen controlled by a pot, (or a digital pot controlled by a microprocessor). For an aware driver regen under direct control of the driver (press harder on the brake pedal, more regen) is simple and works better than automated "profile" systems (econ, power, etc.) none of which know what's ahead on the road... often the most energy efficient option is coasting, maintaining hard-earned kinetic energy. There is no current system implemented in EV's that can do as well as a good driver with full control over regen amount and timing. Especially annoying to me are the systems the apply regen on trailing throttle: with each undulation in the road, the system toggles between power and regen (which feels clutzy-jerky, but also wastes kinetic energy that an intelligent driver can put to good use.) If you really need to come to a stop, regen is the way to do it, and then you want the maximum amount you can get while still being safe (not locking wheels on slippery surfaces, for example).

The idea of a series hybrid is to keep the engine running at peak efficiency or not at all. Lean burn operates only under light load, so you really don't want to help the engine stay in a light load scenario. If it is trending into that area, it should be off entirely. Most Hondas are less efficient in lean burn mode than in normal mode... in other words the actual bsfc is worse at 10 hp in lean burn that at 50 hp in stoich mode. So you want the engine always running at 50 hp or not at all. This requires series hybrid architecture, so that when the engine is running at less than 50 hp (meaning the battery charging load has dropped off) you shut it off.

The beauty of a simple series hybrid (unlike the inefficient Volt multimode system) is that the engine runs at peak BSFC or not at all. Any system that drifts away from that concept can quickly become inefficient (thus the crummy Volt gasoline fuel efficiency numbers relative to the Prius). A series hybrid does energy conversions in which efficiency is lost, so getting high efficiency requires optimizing everything, to make up for the gasoline-to-electricity-to-chemical-to-electric-through-motor losses.

Just try to model everything as closely as you can before laying out money. It is hard to match a really thoroughly-engineered hybrid (like the original Insight or the Current Prius) in terms of carrying ability vs fuel usage.

Quote:
and because it's not powering the car all on it's own that seems like enough to give it an added boost to keep it in lean burn all the time
Sounds like you are thinking of a parallel hybrid. In a true series hybrid, only the electric motor powers the car. In a parallel hybird, the ICE and electric motr can work together, in parallel.

BTW, be aware that if you drive the motor at twice engine speed you will have halved its torque for propulsion purposes.
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