RickAvery

Given the same battery & prop, is the amount of amps that a brushless motor draws at max throttle different with 6 turn or 8 turn motors?
Rick

Matt Kirsch

My Feedback: (21)

Yes. The number of turns indicates the number of turns of wire that are wrapped around each electromagnetic pole in the motor. More turns means longer wire, and longer wire has more resistance. The higher resistance means less current will flow, given otherwise identical conditions.

You can only compare turns on otherwise identical motors. A Hacker B50 with X turns can only be compared to another B50 with Y turns; it can't be compared with an AXi, for example.

RickAvery

Thanks again Matt! I often wonder where you find enough time in a day to respond to all of the questions you do.
Rick

Redback

A bit more info for the curious!

Another factor in the turns equation is the fact that more turns gives more magnetising force for a given current, and potentially more power.

Magnetising Force = Amperes X Turns

You therefore have a trade off when designing a motor, more turns = more magnetising force per amp, BUT, more turns = more resistance and hence less amps.

Terry

RickAvery

Redback / Matt,
So the way I understand it is that motors with fewer turns, say, 2 to 5, are best suited for high RPM applications i.e. wing pushers where a small prop is used and high speeds are desireable, and higher turn motors, say 8 and up, would best be suited for a gear box and a large prop to provide quick acceleration and climbing power? And, that the motor with fewer turns will draw higher amperage at WOT.
Rick

Redback

Rick,

I'm going to pass on your last question as I don't have enough knowledge of motor design principles.

BTW, what's WOT, couldn't find it explained with a search?


Terry

Matt Kirsch

My Feedback: (21)

You're starting to get it, but you're not quite there...

First, you can't put a specific number on the "cutoff point" between hot and cold motors. One manufacturer's "3-turn" motor can be just as hot as another manufacturer's "27-turn" motor. As I believe I mentioned, turns can only be compared when you're talking about a single motor design from a single manufacturer. The general idea is, the fewer the turns, the hotter the motor, though.

Hot, low-turn motors are best geared in most situations. Mild, high-turn motors are more suited to direct drive, turning larger props without the need for a gearbox. That's only a sweeping generalization, though. Some motor designs' "mildest" wind is too hot to turn a useful prop direct drive. Some motors designs' "hottest" wind is too mild to run in a gearbox. To further complicate the situation, many of the "hot" motors can be used in direct drive high-speed applications as you guessed. Motors are very flexible.

Motors with fewer turns will draw more Amps at WOT, IF EVERYTHING ELSE IS KEPT THE SAME (very important, hence the shouting ). That is, same prop, same gearbox, same battery... Change the battery/gearbox/prop in addition to the motor, and the statement becomes untrue.

RickAvery

Thanks again guys for the insight. Trying to get a grasp on e-flight is quite a challenge, but also part of the fun. Your comments have opened up yet another small portion of the big window.
Terry, WOT = Wide Open Throttle.
Rick