serious_sam
10 kW
What is the couple mode?PITMIX said:
Nucular electronics - complete kit for ev!
- Thread starter VasiliSk
- Start date
PITMIX said:
I know about that.
The reason why this happens is because if you exceed a given motor RPM, the BEMF (voltage on motor side) could reach a dangerous level and controller tries to avoid to get damaged from that and so it slows you down until the voltage is safe.
What happens if you release throttle very very slowly (or gas pedal in your case)? When doing so it did not brake anymore in my case.
It might also help to set a speed limit and turn it down until this doesn't happen anymore, but you will loose a bit of top speed when doing so.
serious_sam
10 kW
Of course, couple=torque. Sorry, I should have recognised that!PITMIX said:
serious_sam
10 kW
Very interesting. Did you get this info from Vasiliy or Nuc staff?madin88 said:
In my understanding, the Nuc limits top speed in FW mode to ensure the back EMF never reaches dangerous levels. I'll see if I can find the reference
serious_sam
10 kW
serious_sam
10 kW
In engineering, a couple is two equal forces which act in opposite directions on an object, but not through the same point, so they produce a torque. Couple=torque.PITMIX said:PS : couple in French is torque in English
serious_sam
10 kW
Sounds about right.Merlin said:
But FW is inefficient, so using it all the time just burns power and overheats the motor. It's like a turbo boost button. Only good in short bursts.
Trying to get more speed with a lower voltage pack and using FW is a false economy. You'll need a much bigger pack anyway (more Ah) to pay for the wasted amps used by FW.
If you want more speed, better off using maximum voltage pack, and a fast motor winding.
Just my opinion.
fw is used everywhere in evs world. its not that bad in effiency.
it suffers yes, but not that hard that you need different batterys.
boost is something short for me. field weakening starts smooth and you dont need to push the limits on every ride.
if your normal voltage reaches 50kph and you ride 60kph you will not notice any difference in Efficiency (except of the higher need in power for 10kph more aka windresistance)
in normal usage to gain 10-15kph more i think your Efficiency loss is below 5%
on a high speed run normally ppl dont care about efficieny
it suffers yes, but not that hard that you need different batterys.
boost is something short for me. field weakening starts smooth and you dont need to push the limits on every ride.
if your normal voltage reaches 50kph and you ride 60kph you will not notice any difference in Efficiency (except of the higher need in power for 10kph more aka windresistance)
in normal usage to gain 10-15kph more i think your Efficiency loss is below 5%
on a high speed run normally ppl dont care about efficieny
serious_sam
10 kW
You've got me wondering now. Tomorrow I might do some runs with/without FW, and takes notes of the power requirements and temperatures. I'll report back here what I get.Merlin said:
you can try, but "feelings" about how much it makes a different is not really measureable because of so many factors.
biggest problem is comparing "consumption/heat/efficiency" with different speeds.
a dyno would be needed to have usable data.
or 2 same bikes with same controllers but different batterys...like 16s vs 20s and both tested side by side with 2 ppl who have same weight doing 10x 10km runs at speeds above the 16s batterys stock speed w/o fw enabled.
and here we are allready with the problem. for example a surron with 16s runs easy 70kph.
at 70kph your windresistance is the biggest factor in efficiency.
i bet one of my nuc waiting queue places your wh/km make no difference if you do a 20miles run 16s(fw enabled to reach 80kph) vs a 20s battery w/o fw enabled....side by side no slipstream.
biggest problem is comparing "consumption/heat/efficiency" with different speeds.
a dyno would be needed to have usable data.
or 2 same bikes with same controllers but different batterys...like 16s vs 20s and both tested side by side with 2 ppl who have same weight doing 10x 10km runs at speeds above the 16s batterys stock speed w/o fw enabled.
and here we are allready with the problem. for example a surron with 16s runs easy 70kph.
at 70kph your windresistance is the biggest factor in efficiency.
i bet one of my nuc waiting queue places your wh/km make no difference if you do a 20miles run 16s(fw enabled to reach 80kph) vs a 20s battery w/o fw enabled....side by side no slipstream.
@madin88 do you think that using the Qs 138 on a vehicle over 400kg and with a gear ratio greater than 7 engine revolutions for 1 wheel revolution accentuates the problem ?
I think that the inertia created by the weight of the vehicle and the speed of rotation which is at the maximum of what accept the engine in FW, increases the phenomenon. The FW must be adjusted very weakly in this case, so as not to damage the motor.
I think that the inertia created by the weight of the vehicle and the speed of rotation which is at the maximum of what accept the engine in FW, increases the phenomenon. The FW must be adjusted very weakly in this case, so as not to damage the motor.
I am mainly trying to understand how it works. With my 56T pinion the ratio is 9.3.
In this case the FW is essential to exceed 45km / h but with my 44T pinion the speed is 56km / h without FW it is more than enough. Thank you for the information.
In this case the FW is essential to exceed 45km / h but with my 44T pinion the speed is 56km / h without FW it is more than enough. Thank you for the information.
serious_sam said:
FW is only inefficient if you use it on motor with surface mounted magnets.
On IPM motors it usually is a good thing since on most of them you can gain RPM and torque so you would even see higher ETA and less heat when using it (over the entire RPM range then)
The problem i think is the controller has 100V components limit and if you have 20s battery or more, then there is not much room for a gain.
In my case it was about 30-40% gain in speed with 20s (bike went from 50kmh to around 70kmh on the flat), but then it did the regen thing at throttle off.
If you have only 13s 48V battery you certainly can get 100% or more speed gain.
serious_sam
10 kW
Or I can just ride on the same path over and over and look at the screen to see power/speed/temperature. Sure there is more measurement error, but I'm not looking for exact perfect data, but if there is significant difference, it should be obvious.Merlin said:
serious_sam
10 kW
I guess the majority of us are using surface mounted magnets, so it didn't cross my mind to consider different effects on different motor types.madin88 said:
But I do think that it's interesting, now you bring it up. Thanks for raising that. Do you know of any references or further reading for more detail on specifically why FW is more efficient on IPM motors?
serious_sam
10 kW
Back from the ride. I found a section of flat road, and rode back and forth, over and over. Accelerated smoothly to minimise motor heating during the take off part of each lap. Used no regen. These power figures are based on the peak number that I saw on the first lap of each test, then I continued doing laps to get steady state motor temperature.
No FW:
Max speed = 75km/h
Power in = 3100W
Theoretical Power = 3100W (CdA adjusted to match power in)
Max motor temp = 90degC, reached steady state during second lap.
With FW:
Max speed = 91km/h
Power in = 5900W
Theoretical Power = 5540W (based on above CdA)
Pdifference = 360W
Max motor temp = 130degC, power cut at lap #2.5 (this is where I have the temp limit set atm for the MXUS3k)
Comments:
1) Based on these numbers, I change my opinion. I stand corrected. The 360W difference between measured and calculated is small, probably less than the measurement error (due to variation in conditions, etc). I was expecting much bigger numbers. Seems like FW efficiency isn't anywhere near as bad as I originally thought.
2) Seems like ferrofluid (genuine Statorade) doesn't work above a certain speed ? I noticed that after I did the FW runs, the motor would overheat again much more easily than normal, even at lower speeds and after it had cooled somewhat. Possibly the FF creeps away from the air gap due to the centrifugal force, and doesn't immediately return. Not sure. Anyone else had similar experience ?
No FW:
Max speed = 75km/h
Power in = 3100W
Theoretical Power = 3100W (CdA adjusted to match power in)
Max motor temp = 90degC, reached steady state during second lap.
With FW:
Max speed = 91km/h
Power in = 5900W
Theoretical Power = 5540W (based on above CdA)
Pdifference = 360W
Max motor temp = 130degC, power cut at lap #2.5 (this is where I have the temp limit set atm for the MXUS3k)
Comments:
1) Based on these numbers, I change my opinion. I stand corrected. The 360W difference between measured and calculated is small, probably less than the measurement error (due to variation in conditions, etc). I was expecting much bigger numbers. Seems like FW efficiency isn't anywhere near as bad as I originally thought.
2) Seems like ferrofluid (genuine Statorade) doesn't work above a certain speed ? I noticed that after I did the FW runs, the motor would overheat again much more easily than normal, even at lower speeds and after it had cooled somewhat. Possibly the FF creeps away from the air gap due to the centrifugal force, and doesn't immediately return. Not sure. Anyone else had similar experience ?
j bjork
100 kW
serious_sam said:
As I remember from Justins tread it was concluded that more was needed at higher rpm. A few ml was enough on low rpm, but on higher rpm at least 10ml I think.
Merlin said:But how did adaptto and asi sort those things out?
With these controllers you gain massive more speed.
Asi btw is limited to 90v only VS 92v nuc.
There must be something "different" how fw is used
That only know the devolopers.
One assumption is that Nuc want's to protect the Controller in case of fault with voltage supply.
I guess that bad things would happen if a fuse is blowing or if BMS cuts out at the moment when someone is pushing max power with FW, and BEMF being higher than max rating of controller parts (100V).
This is of course only an assumption..
How is phase current of Nuc definded, is it peak or RMS?
If it's rated for 500A RMS it would be 700A peak
while a 500A peak rating would be around 350A RMS
serious_sam said:
Open your motor and take a look. I am sure that one part did evaportate and another part got soaked up by the stator (between lams), windings etc..
I did put 10ml into same motor and after 2 years and 3000-4000km it was gone, and furthermore all the magnets were loose because the FF did react with the glue and dissolved it.
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