RaserTech, brushless power from induction...

[zeropointbug]

Is it? I suppose it does seem pretty damn flat with wheelies on demand. You wouldn't happen to have a graph of as many brushless motor torque curves?

Also, what is the maximum the 540C-7XL motor is capable of putting out?

thanks

[MetalMan]

Originally Posted by zeropointbug

Also, what is the maximum the 540C-7XL motor is capable of putting out?

thanks

I think in order to answer that, the question would be "how long?" Since torque is proportional to amps, the motor could put out as much torque as the input can supply. However, as the amp draw increases (after the peak efficiency), efficiency will drop. After an amount of time, the motor would become very hot due to the power converted to heat (from the low efficiency). And the longer the motor is putting out the high number of amps, the hotter it will get.

[zeropointbug]

yes I know, but there is a magical behavior called back EMF which is going to limit the torque at higher rpm's, fundamental to what a motor is. But i said max power output, not the max torque output which would be at 0 rpm (if no cogging).

[zeropointbug]

Just one other thought, LMT should start using Bifilar coils in their motors (or why doesn't any motor manufacturer use them.) They would drastically cut self-inductance of the winds would it not?! This would mean less loses in the motor, easier on the controller, and higher power densities i think. Any thoughts?

***A Bifilar, where two or more 'winds' are connected togethor via the end of one comes back and connects to the start of the other. Imagine a two planar spirals, the inner of one 'wind' will come back a loop into the second spiral 'wind'.

[Serum]

What about the EMF?

Controllers have a hard time sensing the possition of the rotor, with bifilar windings it would be even harder.

Costs; you are 'complaining' about the costs of a BL motor already, winding it bifilar wouldn't make it cheaper.

Did you ever observed a stator? it would be hard to nicely route the bifilar windings to start with.

[MetalMan]

Originally Posted by zeropointbug

yes I know, but there is a magical behavior called back EMF which is going to limit the torque at higher rpm's, fundamental to what a motor is. But i said max power output, not the max torque output which would be at 0 rpm (if no cogging).

Looking back at your post, I didn't see any mention of power, so I assumed you meant torque.

[Serum]

Zero; Reading you explanation on the bifilar windings; you mention a spiral. but bifilar has got nothing to do with a spiral; that's a Caduceus winding

[zeropointbug]

A bifilar can be either/Or, a caduceus coil is a bifilar coil. I wam talking about a parallel-wound, series connected wind.

1. parallel-wound, series connected ***
2. parallel-wound, parallel connected
3. counter-wound caduceus coil, series connected
4. counter-wound caduceus coil, parallel connected

How would it affect the controller sensing the rotor position? Wouldn't this just reduce the amount of energy the controller has to deal with during switching?

[Serum]

Caduceus is not good for a motor.. More air, less efficient.. anyway;

bifilar reduces EMF as well. this EMF is used to locate the rotors position by the speedcontroller.

[zeropointbug]

No no, what i mean is back-emf and self inductance are two diff things, right? The back-emf has to do with the stator spinning within the magnetic field of the rotor (visa versa) thats how the controller knows what position the rotor is in. self-inductance is the amount of energy stored in the winding, and because of the amount of inductance, that create a kick-back to the controller while trying to switch from one polarity to other to effectively make the rotor spin. Self-inductance does, as far as i know, increase the switching time of the controller.

[Serum]

Yeah, but like i said; EMF will be lower with bifilar, no way around it, the signals are working in opposite direction from the loose wires one winding is made of. so locating the rotor will be harder for the controller.

[zeropointbug]

I said series-wound bifilar, this is not working in opposite flux, otherwise the motor would not spin :024:

think of two coils wound in parallel, then the bottom of one connected to the top of the other... this would affectively cut the sefl-inductance in half.

[Serum]

where did you said serie wound?

[zeropointbug]

two posts up ^

[Serum]

I said series-wound bifilar, this is not working in opposite flux, otherwise the motor would not spin

This?