Bjorntsc said:
How did you get the CA120-70 down to 5A.
I heard they were about 20A no-load at 48V.
Also what controller could you use to find its potential?
150kv with 28 magnetic poles at 48V got me to 100800 electrical rpm. To get the potential out of the motor (puts out its power/weight equivalent of a C80100) you need to run it at a higher voltage right?
its a bit deceptive using amps not watts, but we regularly hear of 20-28a no load current at 48v with this motor and for some reason an initial judgement has been passed down by the ES crew a couple of years ago and has remained permanent. -i think someone popular here called it a pig or a dog and that was that..
the ca120 is no different to any of our decent 85-90% permanent magnet iron statored motors, hubs, rc, brushed or not. -if you take the no load consumption and times it by about 15, you arrive (roughly) at peak efficiency and therefore a good place to aim for at full power, it took me days to boil it down to this, oversimplified, but there you go.
basically, lurking behind the fairly large no load loss is a correspondingly large ability for making power via its super low resistance, this made everyone scared cos back then cheap controllers were not up to the job, now it seems they are.
so, if you rev this motor to the point where you are using 28a no load, you must be aiming for about 420a full load current and thats now about 20kw max input and not far off peak efficiency (about 87% in this case) for that battery voltage, so its very keen for a motor the size of about 45 cd's in a stack, but ok for burst use at 20kw (25% duty actually) with fan cooling.
so any normal electric motor that is set up for 20kw running sweet as at peak efficiency of 87% would have around 2600w of losses, half winding losses, half no load losses, thats not far of this motor at 28a*48v= 1344w no load loss, at this voltage.
its optional if you want to push it that hard, the ca120 will cope with this 20kw load with 87% eff, just like say a $1000, 8", 11kg perm 132 does, but im currently tuned for 5kw, so my no load losses are about 350w
in the end i think people do get this, when you say it has too much power for a 40kg bike, and it only weighs 2.2kg..
-and what to do with the spare space and 5 to 10kg that im not carrying? :wink:
so heres how:
grind BETWEEN stator teeth to glue 3 hall sensors in, ill have to put up a pic for thier positions etc, in the middle of a tooth or external halls both gave misses at high phase amps.
shield the hall wires, add extra 2.2k pullup resistors, and .1uf caps and then to burties timing module, get it to learn the hall sequence, then disable learning and try 15deg of advance static and 5 deg per 1000 rpm, will need fine tuning.
change the motor windings to wye, can be done without too much grief, just at the wires external to the motor, should now be 84kv, so 60v and 100a battery current gives you 5000rpm and good for about 6kw.
im using a $489 10kw kelly keb: http://kellycontroller.com/keb7210024v-72v450a10kw-bike-brushless-controller-p-1182.html
it has extra low esr caps at the bus bars, and it will need the latest firmware and a different user interface thingy with an extra screen of adjustments.
contrary to what i and others would expect this controller has been completely reliable, they happened to be doing new firmware when i got to dynoing the motor so i just kept hassling them for changes till it worked good and with heaps faster responce.
there is also a funny little regen thing that kellys do even without being a regen model :? (3kw+ skidding the rear tyre on liftoff), can be fixed by hassling burtie for a timing chip with high speed map changeover switch inputs etc.
that should give about 6a no load, at 48v, 4000 rpm, now suited for 4.3kw, set the kelly for torque throttle, and if you gear lower than 9:1 your off the back.
its quite easy, no really, now that it works it's not that hard or expensive, and ill help folks who want to make it happen.
Bjorntsc said:
No, but do you have a link?
yes: http://www.hobbyking.com/hobbyking/store/__19964__Turnigy_RotoMax_100cc_Size_Brushless_Outrunner_Motor.html
now it get's interesting, theres also another that looks optimized for more rpm less torque, lower no load losses, and i reckon may be a hacker a200.
i had $1300 down on the very same a200 for this project 2 years ago, it never arrived i got a refund and went all hobby city and now they sell them in black at a third the price: http://www.hobbyking.com/hobbyking/store/__19964__Turnigy_RotoMax_100cc_Size_Brushless_Outrunner_Motor.html
notice the shorter stator teeth, and .2mm laminations miles
big cooling holes in the above motor, ill bet its a few % more efficient at light loads and good for way more revs vs the waay longer iron teeth and nearly double the copper in the ca120 that is made for torque: http://www.hobbyking.com/hobbyking/store/__14427__Turnigy_CA120_70_Brushless_Outrunner_100cc_eq_.html
