Work and Efficiency of P4 motors

[rpercifield]

As a person who works in electronics and BLDC motors 100% efficiency is not possible. Looking at the data it appears that you are looking at distance traveled per power delivered. This is not dimension less but like a mobile transportation miles per gallon, km per liter, etc.. For the efficiency to become a percentage both terms must be of the same units, such as watts in compared to watts out (i.e. power supply, motor shaft outputs.....). Thus, it as an exaple my power supply uses 75W to deliver 72W at the output giving you 96% efficiency. This data is useful to determine optimal flight characteristics and other parameters, and has now given me something else to play with. Thanks for the information to gain access to the data.

 

[sar104]

Let’s go easy on the spin here and not make this into a frat spat.
The only thing to be amazed here is the data stored from each, mind you each, flight on this machine.

No problem, although engaging in a discussion on technical points is perfectly legitimate and reasonable; no need to characterize it so negatively.

Having spent many hours analyzing DAT files, I completely agree that these represent quite impressive data sets. And, again, I was not criticizing the intent of your original post - just questioning some of the methodology.

 

[sar104]

As a person who works in electronics and BLDC motors 100% efficiency is not possible. Looking at the data it appears that you are looking at distance traveled per power delivered. This is not dimension less but like a mobile transportation miles per gallon, km per liter, etc.. For the efficiency to become a percentage both terms must be of the same units, such as watts in compared to watts out (i.e. power supply, motor shaft outputs.....). Thus, it as an exaple my power supply uses 75W to deliver 72W at the output giving you 96% efficiency. This data is useful to determine optimal flight characteristics and other parameters, and has now given me something else to play with. Thanks for the information to gain access to the data.

Right - that was the central point under debate here. I think that the term efficiency is being used a little more loosely in some areas, and leading to confusion and to the unphysical 100% quoted above. I guess it doesn't matter too much as long as it is clearly defined in the context in which it is being used.

 

[With The Birds]

There is temperature data on a per motor basis (Motor:EscTemp:<motor>). But, it can't be the temp of the motor because each motor only has three wires and those are used to power the motor. So the assumption is that it has to be a temp sensor in the ESC circuitry.

It would be interesting to learn what the motor temp actually represents. It is possible to determine motor winding tenp without an additional sensor in the motor, if ambient temperature and starting resistance are known you simply need the motor winding resistance at elevated temperature to calculate the value.

 

[amstar]

As a person who works in electronics and BLDC motors 100% efficiency is not possible. Looking at the data it appears that you are looking at distance traveled per power delivered. This is not dimension less but like a mobile transportation miles per gallon, km per liter, etc.. For the efficiency to become a percentage both terms must be of the same units, such as watts in compared to watts out (i.e. power supply, motor shaft outputs.....). Thus, it as an exaple my power supply uses 75W to deliver 72W at the output giving you 96% efficiency. This data is useful to determine optimal flight characteristics and other parameters, and has now given me something else to play with. Thanks for the information to gain access to the data.

Hence also the fact that efficiency cannot be 100%, we know that as I tediously explained in a previous post.

 

[With The Birds]

Hence also the fact that efficiency cannot be 100%, we know that as I tediously explained in a previous post.

And so we are back where we started- what does your 100% motor efficiency graph in the OP tell us?

 

[BudWalker]

It would be interesting to learn what the motor temp actually represents. It is possible to determine motor winding tenp without an additional sensor in the motor, if ambient temperature and starting resistance are known you simply need the motor winding resistance at elevated temperature to calculate the value.

I had thought about doing an experiment by wrapping a heating pad around one of the motors then looking at the temps in the .DAT. I didn't get around to it because it seemed to me that what you described may be possible but the engineering aspects would make it unlikely.

 

[With The Birds]

I had thought about doing an experiment by wrapping a heating pad around one of the motors then looking at the temps in the .DAT. I didn't get around to it because it seemed to me that what you described may be possible but the engineering aspects would make it unlikely.

Yes.... I had thought the VFD on my CNC router only had the supply wiring to the spindle motor, it displays temp and in effect is just a upscaled (6kw) version of the phantom propulsion. Curiosity got the better of me- I have since determined there is a temp sensor in the spindle.

 

[Erised]

This is how my P4 is efficient: At about 30 mph I can fly well over 40,000 feet total for about 20 minutes and land around 20%. When I got my craft the battery was $250 Canadian ($1.99 US) Got 4 batteries, but if I would have done this with one battery and flown my 7.5M feet so far, that's about 17 cents per mile. As far as efficiency go's I think the motors are way better than our batteries.(and cheaper too) The way I see efficiency anyways.

 

[P4PCommander]

If your intent is to ascertain optimum speed to achieve maximum flight distance from a given battery consumption the range threads demonstrate this, it is just slightly less than your speed for this flight.

Energy consumption would be watt sec * time. I don’t understand how 1/energy consumption gives you efficiency? Efficiency with respect to this exercise is seemingly how far you fly for a given mah consumed at one constant speed compared to another (comparative rather than absolute). You might do the same exercise for max flight time, in which case you will find the speed would be closer to hover (least efficient) but significantly less than that to arrive at maximum distance.

I wish Einstein had a Cell Phone, maybe we could clear this up, cause right now I'm Confused!!