Sustained vs. Peak Power Measurements Explained

[Jason McNeil]

I'm going to try to be disciplined & create a couple blog entries a week about all thing related to Wheels. Here's today's entry attempting explaining the difference between the peak & sustained motor output.

"All Electric Unicycles operate in the same basic way: hundreds of times a second, the gyroscope sensor is monitored to detect the amount of lean (or inclination) & applies counter force with the motor. These 'power' pulses of the motor are very brief, typically lasting less than a hundredth of a second!

Because of this brevity, it is not unusual for the power profile to look completely chaotic, without any kind of underlying meaning or pattern. There are some manufacturers who quote the 'peak' power output of the Electric Unicycle as THE motor power rating, but as can be seen in this graph, this practice is highly misleading—supposing you're cruising along a wide open path,  you obviously want to know how hard you can push your Electric Unicycle/Wheel to prevent the power from cutting-out. Using the peak power measurement, it gives you no indication of this, since you can get a small gust of headwind & the power measurement goes through the roof. A much more useful guide/measurement is the sustained power (average) which is now gaining widespread acceptance. This better indicates how powerful the Wheel is over a sustained period of time, for situations like high-speed travel & hill-climbing.

Conclusion: when considering the purchase of your Electric Unicycle, make sure you verify whether the motor power measurement is the 'Peak' or the 'Sustained'."

https://www.ewheels.com/motor-power-really-mean/

[Gimlet]

As far as I can tell there is also a huge variation in how to define sustained power.

Some seem to think that if a motor can deliver a level of power for 5 minutes, sometimes even less, then that is sustained whereas others including me would like the sustained measurement to be of continuous power output for the total time the batteries can provide the required power.

[jbwheel]

9 hours ago, Jason McNeil said:

Conclusion: whmotornsidering the purchase of your E lectric Unicycle, make sure you verifymaybether the motor power measurement  is the 'Peak' or the 'Sustained'."

Maybe consider first if the wheel (not only motor) can provide the peak or sustained value with the included battery pack. 340Wh or 850Wh is not the same and 170Wh lipo is better than 340Wh or maybe even bigger liion pack. Especially when some nmotors display 3000W peak and  800W/1500W sustained.

[Jeffrey Scott Will]

18 hours ago, Gimlet said:

As far as I can tell there is also a huge variation in how to define sustained power.

Some seem to think that if a motor can deliver a level of power for 5 minutes, sometimes even less, then that is sustained whereas others including me would like the sustained measurement to be of continuous power output for the total time the batteries can provide the required power.

This is the kind of thing I'd like to see compared between ACM and KS16. There are a lot of people (probably wrongly) stating that the ACM is almost twice as powerful as KS16. It seems doubtful, but I'd like to see the comparison.

[Cloud]

There is a lot of confusion with these motor power terms. Rated power usually pertains to the power the motor puts out when working most efficiently under sustained operation. This doesnt mean that the motor cannot produce a higher torque continuously. I believe the motor can produce a continuous torque equivqlent to about 10-20% of the rated power.

The most confusion is with the maximum power. Maximum power cannot be twice the rated power. I believe that when euc manufacturers say "maximum" , the numbers they list really is the power that can provide the locked rotor torque or rather the rated voltage multiplied by the stall current ( the condition when the rotor is locked or when the load is such that the motor cannot turn). This torque can only be put out momentarily and cannot be sustained over time.

[OliverH]

I think that most manufacturer make an estimation. I only count on values measured with the same method, e.g. ISO 60034-1. It's more relevant at which rpm can a motor produce which power (red curve) or torque. I tried to show this in this drawing (power over rpm), based on fiction eWheel (in the MSuper class) and balancing power was estimated. All values are max values where the full possible load when lines are crossing. So a treshhold would be at least 3-5 km/h back.

 

The power curve would present the power curve on a fully charged battery and full power out of the main board. If a behaviour handling comes in and possible power is reduced (current limiting) or capacity is simply not available (low battery) the red curve would look different.

I think the advertised power values are just a number, a power rating and it's a marketing value.