evdragra...@email.com wrote:
A sepex motor can do great regen.
I agree! I used a sepex motor (Aircraft starter-generator) in my first EV, with a home-made contactor controller. Awesome 500 amp regen, even from this "tiny" 70 lbs generator! It was enough to skid the back tires on dry pavement.
Steve: What is the goal?
I think that's an important consideration. If this is a "backyard" budget project, with an old truck and a surplus motor they found somewhere, then playing around with this sepex motor and your own controller could work.
But if this is a serious project, with serious money, and intended to make something commercially viable, then I think it makes more sense to buy a new or used integrated motor and controller package from someone who has been building them for electric city buses etc.
Some folks suggested voltage switching and field control. I imagine a 2600 lb motor has a monstrous amount of inductance, you'd have to plan for that. You might need to do a bunch of contactors in parallel and series to handle breaking current on something with so much inductance.
This is exactly the sort of controller I had. It had contactors to switch the battery pack to two different voltage (half, and full), and contactors to connect the armature to the pack, either directly or with a "starting" resistor in series. The accelerator pedal moved a big rheostat, which controlled the motor field current.
This was in a Datsun pickup truck, with the stock transmission and clutch. To drive it, you started the motor with half voltage, starting resistor, and full field current. It would idle at about 1000 rpm. You started moving with the clutch and transmission normally.
Once the clutch was fully released, the starting resistor was bypassed. The accelerator pedal now controlled the field current, and thus motor speed. The accelerator doesn't act like a normal ICE; it acts like it's the 'set speed' for a cruise control. That is, for a given position of the accelerator, the vehicle wants to run at a constant speed, whether flat, uphill or downhill. It will automatically do regen downhill (trying to hold the motor speed constant), or if you let up the pedal.
At about half position of the accelerator, it switched from half to full pack voltage. This doubled the voltage to both the armature and field, so there wasn't any big change in speed. But it allowed you to go a lot faster as field current was further reduced.
It was a crude system, but quite driveable. You'd also put teeth marks in the steering wheel if you dared to suddenly let up the accelerator pedal in a low gear due to the large amount of regen!
A car controller might not be able to handle so much inductance unless you ramped the current very slowly.
Inductance is the *friend* of motor controllers! They *like* high inductance; in fact, they have trouble when there isn't *enough* inductance.
I'd humbly suggest putting a reed switch on the field that disables the armature contactors unless there is sufficient field current.
Yes; it is vital to have fail-safes so it is impossible to power the armature without field current. The armature looks like a DEAD SHORT with no field current! Things will go BANG!
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