Gossip has been bouncing around for a while about the motors that are in the Zero 2012 lineup. I think it’s pretty well confirmed now, they’re using a modified version of the Motoenergy ME0913. This is huge.
The start of this little journey was here:
…from the Zero spec page.
Now, if you’ve been paying attention, you know a double-stator axial flux permanent magnet, brushless motor is pretty exciting. First, the axial motors are the motors that give you great efficiency, like the Agni, Perm and ETEK designs, and they usually have that fairly remarkable laminated iron core with the copper windings that run in an armature between two magnets, that Cedric Lynch first cut out of tin cans for his very first motor. This design was the center of a huge patent and licensing mess, and resulted in the Agni motors, still produced by Cedric in India, LEMCO making an almost identical design in the UK, and Perm still cranking out their axial designs. It also left us with a legacy of Briggs and Stratton ETEKs floating around with very interesting provenances.
Now. The guy who took the original Lynch design license and made the production version Briggs and Stratton ETEK is our good friend John Fiorenza. Yes. The guy who is Motoenergy. John designed and produced the (radial flux) ME0709, and several retailers branded it as the ETEK RT (much against John’s wishes and intentions). It always bothered me, though. He had a great design, why didn’t he produce a motor like the ETEK or Lynch? I think it pretty obviously was a licensing issue, and knowing John the bit that I do, I doubt he was willing to stomp all over Lynch’s design rights as Perm did.
That’s why the ME0913 is so exciting. It’s a design that’s similar to the ETEK, but better. Simply by putting the coils on the outside and the magnets on the rotating shaft, you’ve allowed yourself to cool the coils better. You can even pump liquid around them. And you can easily set it up as a brushless motor… no, you really have to, since there’s no great way to run brushes on a configuration like that.
If you want to see the motor dissected, check out the Ripperton Electric Track Bike thread on DIY Electric Cars. Great stuff. Complete madman, that Ripperton guy.
Here are the specs of the motor, by the way:
The new Dual-stator motor from Motenergy, Inc (formerly Mars Electric) has an output power of 10.5 KW Continuous (at 48 volts), and 30 KW Peak (at 96 volts).
Designed for long life. No brush maintenance. The motor is 92% efficient at voltages between 24 to 96 VDC. Continuous current of 125 amps AC (180 Amps DC into the motor control). This is a 3-phase, Y-connected Permanent Magnet Synchronous Motor with an axial air gap and 3 Hall sensors at 120 degrees electrical timing. It has two stators with a rotor in the center.
- This is a 4 pole motor (8 magnets).
- The Phase to Phase winding resistance is 0.013 Ohms.
- The maximum recommended rotor speed is 5000 RPM.
- Voltages from 0 to 96 VDC input to the control.
- Torque constant of 0.15 Nm per Amp
- The Inductance Phase to Phase is 0.20 Milli-Henry.
- Armature Inertia is 45 Kg Cm Squared. Continuous current of 125 Amps AC (180 Amps DC into the motor control).
- Peak current of 420 Amps AC for 1 minute (600 Amps DC into the motor control).
- Weight of 35 pounds. 11) Peak Stall Torque if 90 Nm.
- This is an Open Frame, Fan Cooled motor.
So, after reading that thread you almost get the feeling that John floated the motor out there to get a feel for the response, maybe even as a core design open for some modifications for his OEM clients, who are his main bread-and-butter. That’s what’s so cool about the Zero motor.
From what I’ve been able to find out, (and it ain’t easy, what with Non-Disclosure and all), the Zero version is built by Motoenergy to Zero’s specs. They’ve enhanced the air-cooling by improving the fan and air flow. They’ve increased the amount of copper, improved the magnets, and are using a sine/cosign encoders and controller- the Sevcon Gen3 controller (with, reportedly, over $100K in programming development.
Presumably the controller work was to give you better control over the throttle response and the regen capabilities. Reportedly the throttle curve is smooth as silk – something Zero has struggled with, from a consumer product and liability standpoint, what with some early experiments with de-tuning low-throttle torque, that were, in my not-so-humble opinion, a really bad idea. The motor had to have sine-cosign encoders for that to happen, so while they’re building a custom design, why not make some basic improvements? I can’t help but believe a huge chunk of Zero’s direction came from Ripperton’s work with this motor.
Everything else aside, it’s very exciting to think about what the next generation of this motor design will be. And no, John’s not talking. It’s also great to see such a high-visibility and performance oriented contract going to such a great company, and a great guy.
Congrats, all around! John, Zero, the whole lot o’ ya. It’s an inspiring way to start 2012!
(and a tip o’ the hat to liveforphysics for letting the cat out of the bag…)