Hummina Shadeeba
10 MW
With wind resistance and other resistances adding to the load on the motor what percentage of the motor’s no-load speed is achievable?
What speed in relation to the no-load will you go
- Thread starter Hummina Shadeeba
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speedmd
10 MW
Hummina Shadeeba said:
What is the resistance level of your rig (aero and mechanical) and what is the available power? Impossible to figure without some estimates. From what I understand, somewhere around 80% of no load RPM is where most of the e-bike type motors will run near max power when loaded and still run relatively efficient.
ZeroEm
1 MW
80% in Texas.
Chalo
100 TW
As speedmd alludes to, how fast you go is a function of how much power you have available. If you have an abundance of power relative to your wheel speed, you'll generally get into the range of 80% of the no-load speed, because that's the speed range where power output tends to drop off sharply. So if you have enough power to get up to that speed, you'll reach equilibrium there because power output will fall to meet power demand.
If don't have enough power to get near your no-load speed, then equilibrium will happen at a lower speed (and possibly a much lower efficiency).
If don't have enough power to get near your no-load speed, then equilibrium will happen at a lower speed (and possibly a much lower efficiency).
spinningmagnets
100 TW
A low-amp system will bog down at modest levels of wind resistance. The more amps you have from the battery and controller, the closer you can get to your no-load RPM.
Hummina Shadeeba
10 MW
What if I’m overpowered! Not that such a thing exists but how about 180 amps and a max no-load speed of 43mph? Can I expect to get up to 43mph with a strong drive/motor?
Is it worth adding voltage to increase torque despite doing so would make the no-load speed even further away?
Maybe I can figure just looking at the grin simulator.
Is it worth adding voltage to increase torque despite doing so would make the no-load speed even further away?
Maybe I can figure just looking at the grin simulator.
Chalo
100 TW
Hummina Shadeeba said:
No. You can only reach no-load speed with no load. The more power you have, the closer you can approach it.
By escalating the whole RPM range, it will make power available at higher road speed (even if maximum torque is limited by the controller's maximum current).
Do that. Pay attention to what the red line is doing in the speed range of interest.
speedmd
10 MW
Field weakening would also raise the no load motor RPM.ferret said:
Hummina Shadeeba said:
speedmd said:
How is field weakening different to the voltage increase suggested? Both raise the no load motor RPM, except with field weakening it is adjustable not fixed.
If your setup, for example, gets 43 MPH wheel speed under load, then once you remove the load, wheel speed will raise above 43MPH.
Unless you are changing voltage, amperage and/or timing advance in real time to compensate, the speed with resistance can't reach or exceed the no-load speed.
Avner.
speedmd
10 MW
Good point on the adjustability of field weakening. Playing with the simulator I noticed some significant broadening of the power, rpm-efficiency band plot width using a BBSHD - Phase Runner vs the standard controller pulldown options. That and field weakening would greatly improve the drivability of a single speed setup.
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