adam_one

Yes, and according to my formula, the 3-phase's frequency should be 2333.33Hz provided there's no slip between the stator and the rotor.

Ron v. Sommeren

Adam, since these motors, in combination with the ESC of course, are self-commutating, they have zero slippage.

adam_one

Yes I agree Ron, the 3-phase ESC's actual output frequency depends on the motor's Kv and on actual load, since the ESC needs the back EMF signal before it sends the next pulse, while the pulse's duty cycle depends on the throttle position, right?

warren52nz

I think I'll jump in here. I've been trying to discover how a brushless motor can turn at any speed other than the speed that the ESC is "telling it" to. My helicopter can't keep up the same rpm when it's on full pitch than it does at 0 pitch. So it seemed to me that the rotor would be getting behind the rotating fields which would cause God knows what sort of problems.

But after reading this post, it sounds like the speed of the rotating fields reduces if the motor senses it is not keeping up. Is that right?

Kinda tricky.

Thanks
Warren

Neomike

It"s called slip. The difference between the speed of the rotating magnetic field and the rotor speed. More load more slip. The ability of the drive unit to keep up with the demand frequency, i.e. speed of the motor, is the torque avai;able or current response of the drive unit.
When the motor doesn"t keep up then CEMF starts to have an effect. You probably don"t want to go there, LOL.
The difference in speed between the rotating field and actual rotor speed ( slip) has an effect on CEMF and torque/curent in motor will increase bringing the rotor speed back to within the slip tolerence designed into the motor. Therefore, more load slower = more slip = more torque = back normal rotor frequency or speed.

Anyway I teach a motors and generators/drives class for the elevator industry and you would be surprised how simmilar the motor and drive unit concept is.
Hope this makes some sense it"s kinda late tonight.

mike

comptrguru

Hey, Gang...
If I took the time to really study this topic, my ??'s were prolly answered. I couldn't 'get it', though. Bear with me, please.

Can I simply hook up twin brushless motors to one ESC? Series hook up? If not, how can I run twin brushless? Thanks mucho....

Ron v. Sommeren

It's the motor that tells the controller when to commutate. These brushless motors are the same as brushed motors, only here the reversing of the voltage/current is done by the ESC, based rotor position and speed information from the motor.

Ron v. Sommeren

@Neomike
There is no slip in these motors.

Seed of Chucky

I am fairly new to brushless, converted from brushed, but these little motors are powerful! Because they make a lot less noise when spinning the props, I have almost accidentally bumped into the prop on my workbench while testing! Wouldn't have been pretty.

Because brushed motors are so much louder than the brushless, I just feel they are more dangerous.

But on the other hand, I love brushless! My motor has already lasted longer than any of my brushed ones and I'm sure there is a ton more life to it. Maybe you guys would know just how long a typical BL motor can last for without crashes??

A TRAIN

I have a posted thread somewhere on this site but.---would 2 outruners hooked up in parallel to a esc of sufficient size run EXACTLY at the same speed? I want to do this to a Vought V173 (flying flapjack) which has props on the extreme outboard position.

ron_van_sommeren

Two brushless motors, whether in- or out-runner, in parallel will always be in perfect sync, if they start.

A TRAIN

Many thanks Ron. Now comes the hard part ----building the "thing".

rodparsons

A question Ron. I'm using a brushless helicoptor motor for a cutting spindle on a milling machine.
So what you are saying is that if it is running at 30,000RPM and I start cutting through some material.
The speed will slow down but the ESC will automaticly adjust the timing output to the motor to get it back up to that speed. So in other words the ESC uses the back EMF from the motor as a feedback loop to keep the speed constant.

Is this right????

Thanks
Rod

MatC

To clarify a few points here:

Running two brushless motors from the same esc: you can't, it will not work. They might start and run together, but they won't work right for long. As soon as one slows down, the other may well get out of sync, lose power, run backwards, etc. Not good. If it worked for a short time, they would run at exactly the same speed though.

As regards the ESC and motor working together, it's something like this:
The ESC senses the motor position, and gives the output accordingly. There isn't any one set speed, the ESC just applies power using the motor's position to know which windings to activate. It's like an old clock with a pendulum: the clock senses the position, and adds a little power to make it go more in that direction. Starting is somewhat different, but that's another topic

So it's not that the esc "reduces speed if the motor falls behind", more like "the esc always knows where the motor is, and powers accordingly".

A TRAIN

I assume then that to use two brushless motors on my Vought V-173 (Flying Pancake), I will have to use two brushless esc's. Another great idea goes down in flames! ! mike[]

sky9flyer

Yes, you can run them in "series" for doubled voltage on the power source, but you will need a larger amperage of speed controller. if you want to run them in parallel sequence you need to use two seperate speed controllers with the receiver plugs spliced together.

bil2

My Feedback: (5)

Scott, these guys are ALL wrong. Actually there's a bunch of tiny midgets that run back and forth inside the motor when you flip the switch on/off. The confusion arises because they run in a RECTANGULAR square trapizoidal sinusoidal rectal shaped direction, thus leading to MAGIC! (The easiest explanation is always the correct explanation. Magic works.) No thanks are necessary. Bil2

sky9flyer

unfortunately only in fairytales my friend, only in fairytales. [8D]

credence

My Feedback: (2)

Finally, someone who speaks my language! That explains EVERYTHING!

SigMan

My Feedback: (21)

hi, i just got an e-flight park 450 brushlees motor, and i need to change the shaft direction, but there no instruction on how to do this, do i just remove the collar and tap the shaft thru the replace the collar. they dont give instuctions on how to do this, fraid of messing up my new motor....help! thanks

ron_van_sommeren

The bible for RC motor builders
www.powerditto.de -> English

karam

how are u for all
i am anew here
plz i hope any one here to help me
i am astudent in polytechnic and study mechatronica engineering i search about a small researh about any kind of motors the most important thing on it is how does it work
it will be very good if it include some figures to help in understanding
if anyone want to help me please send me in my email which is
[email protected]
and thanks for all

ron_van_sommeren

Welcome Karam

See
http://www.consult-g2.com/course.html
http://www.innovatia.com/Design_Cent...lectronics.htm
http://groups.yahoo.com/group/electricalmotordesigners/ -> 'Files' and/or 'link' section

stoney666

newbee here can any one tell me if i can put the life back in my lipo backs yes 2 in told dont think i had the brake set on my esc only got one flight of 5 mins of the 2 cell pack and never got to see the power of the 3 cell pack did not now i was went to charge them straight out of the bag just pluged it in and did not get of the ground went to charge it up and it wont charge been told iv stuffed it but bloke in shop is new to lipos 2 help please in info brought another pack to day and a cell balencer and will charge it first and turn on break i take it the break on my esc stops the DC/AC currants dropping to low in the lipo and im new to this foram stuff to so appologies for asking in wrong foram sorry can some one please point me in the right direction thanks and allways fly high the higher you are the further the ground is.: ]

bil2

My Feedback: (5)

Are you using a lipo specific charger? One cannot use just any charger for lipo batteries.