Electric Motor Secret Sauce Happening


BRD is now Alta, and announced their bikes in Florida this week.  Their motor is roughly 30kw, and is only 11lbs.  The Emrax 228 is something like 100kw and 27lbs.  There’s some magic afoot.  Everybody’s always talking about the latest greatest battery breakthrough that’s vapor at best, but somehow nobody’s really talking about these motors.  Oh, yeah.  That Alta motor?  RPM max is 13,000 or something.  Insert “scaring the shit outta me” emoticon here.

You’ve got to understand, RPM in electric motors trumps just about all.  Volts = RPM, and you have an RPM/volt rating for a motor – how many RPM do you get for a given volt input.  Also, RPM + torque = power, right?  So even with a low torque motor, if you spin it high enough and gear it to what you want, you’re going to get huge power output. If you’re interested in electric motor power ratings, especially compared to gas motor horsepower, see my post here: Electric Motor HP Ratings (and Other Secrets of the Universe) vs Gas Also, don’t miss my “Motor Specs: The Elusive 100kw” post to compare a bunch of common motors.

So let’s just look at power-to-weight, because that’s one of the primary concerns with a motorcycle motor.  We’re going to pull from the Wikipedia Power/Weight post.  Keep in mind, we’re assuming the power rating is peak, or, what the motor can do for a few seconds.  Continuous rating is typical of an electric motor for industrial applications, and is significantly lower, based on the idea that an industrial motor has to run all day, every day at a given load.

motor power weight power/weight typical use
Panasonic MSMA202S1G AC servo motor[17] 2 kW 6.5 kg 0.31 kW/kg Conveyor belts, Robotics
Toshiba 660 MVA water cooled 23kV AC turbo generator 660 MW 1,342 t 0.49 kW/kg Bayswater, Eraring Coal Power stations
Canopy Tech. Cypress 32 MW 15 kV AC PM generator[18] 32 MW 33,557 kg 0.95 kW/kg Electric Power stations
Toyota Brushless AC Nd Fe B PM motor[19] 50 kW 36.3 kg 1.37 kW/kg Toyota Prius[•] 2004
Himax HC6332-250 Brushless DC motor[20] 1.7 kW 0.45 kg 3.78 kW/kg Radio controlled cars
Hi-Pa Drive HPD40 Brushless DC wheel hub motor[21] 120 kW 25 kg 4.8 kW/kg Mini QED HEV, Ford F150 HEV
ElectriFly GPMG4805 Brushless DC[22] 8.4 kW 1.48 kg 5.68 kW/kg Radio-controlled aircraft
EMRAX228 Brushless AC electric Motor[23] 100 kW 11.9 kg 8.4 kW/kg Battery Electric Air Plane

Right? See the EMRAX down there at the bottom?  8.4 kw/kg.  Keep that number in mind.  Now let’s look at the Alta motor, at 40hp and 11lbs.  40hp = 30kw, 11lbs = 5kg.  30kw/5kg = 6 kw/kg.  How about the Zero 75-7 motor?  That’s rated at 40kw, and is weighing in at 35lbs, or 15.8kg.  2.53 kw/kg.  Not so impressive when stacked up against the “secret sauce” motors, but still in the “RC toy motor” range of awesome.

Do I know what’s going on here?  Not a clue.  First, let’s guess they’re cooling the shit out of the motor.  Most of the motors that have been used to date have been retrofitted with cooling, but let’s presume these new motors have been built with all the cooling going to the hot bits, so they can run it harder without them getting everything else hotter.  Second, let’s guess they’re doing some Magics in the controller programming and designing the motor specifically so such Magics is possible.  Finally, I’m going to guess they’re designing these motors to be light – never a priority before, until electric motors were starting to be utilized for aircraft application. Come to think of it, this would all be stuff that, for the last few years, we’ve all found frustrating about motor design – no good cooling, heavy construction, like that.

But, let’s go back to the 100kw motor specs spreadsheet and update it with the power-to-weight numbers. Here you go:

Motor Specs AC35 Dual EMS PMAC (x2) EMRAX 228 YASA 400
Peak kW 96kw 76kw 100kw 90 (@350V)
Peak HP 126hp 101.9hp 134hp 120hp
Peak torque 348nm 200nm 240Nm 360Nm
Peak RPM 5000 6500 4000-6000rpm 7500rpm
Peak current 1400A 480A 320A 420A
Weight 150lbs 70lbs 27.1lbs 52.9lbs
Weight (kg) 68kg 31.75kg 12.25kg 24kg
Power/weight 1.41 kw/kg 2.39 kw/kg 8.16 kw/kg 3.75 kw/kg
Cooling air liquid liquid/air liquid
Price $7000? $3700 (kit) $3,500 ~$5000?




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