Brushless MOTOR!!

[Junwei]

hey guys.. i wanna ask..
how does a brushless motor work..
and how to choose esc for it and all..
simply say how to do a brushless set up..

[johndyl]

nah........... brushless motor

http://en.wikipedia.org/wiki/Brushless_motor

u need to get some specs on the motor which is usually supplied by the manufacturer on the max amp draw.., if not u can also run it with a high specs esc(electronic speed controller) and measure the amps with a ampmeter.

then u need to get a brushless esc with a amp rating higher than the max the motor will draw to be on the safe side of things.

eg, if the max amp draw is 25A, u should get at least 25A brushless ESC

[Hengheng88]

this pic will help

[Hengheng88]

this pic will help

pic size too big

[edmond22]

An article I have written a long long time ago, hope it helps.


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Making a sense of electric flight,
what to consider when buying components?

To many of us who have been flying electric for a while, we can all remember the learning curve we go through in getting it right. Inevitably, some of us may have also incurred additional parts like batteries, propellers or motors that will have been sitting around unused deemed as unsuitable for our main fleet of planes etc. I am one of these such people and I am still figuring out if I can ever get these additional parts to complete a plane and the usual trouble is that they are just plain wrong in the first place to start with. This simple guide is written for those who would like to get a better understanding of what is involved and get started with electric flight in the most efficient way while keeping unnecessary cost to a minimal.

Start with a new approach and mentality

When you are buying, there are a few things to consider. It is always good to ask questions but trouble is, it is hard to tell between sales pitch and actual useful information. I bought a glider once, a Wattage Mini Thermalaire kit that requires my own electronics, propellers and motor. Being a gullible first time buyer of electric stuff, I asked the shop to complete the items I need, they proceeded to throw in a 6 by 5 propellor, 2 mini servos and a mini receiver. After paying for the items, the lady kindly informed me to buy an ESC controller, motor and battery elsewhere as they do not have it! The lady even volunteered to say that it is quite easy, I just need any spd 400, 10 amp esc and 8 cell battery to get it to work nicely. So off I went to the next shop in the same building to complete the kit, I was then offered a 2 in 1 can speed 400 motor with a 10 amp rondo esc stuck behind it and a Nimh 8 cell battery. Needless to say, I never got the kit to fly. 6 by 5 prop on the motor draws too much amp and the battery is not quite the right candidate for the job. This resulted in constant ESC low voltage cutoff. Assuming that if I buy the right battery that gives out better discharge would solve the problem, I bought myself another battery that is Nicad instead. On second attempt to mate the items together, the ESC burned out on me because the current draw is 15amp on full throttle with the new battery. I ended up buying a new ESC and motor separate again just to get the kit to fly. I realised I have to do my own research and seek out just exactly what I have in mind. Buy smartly, not blindly and if need to be, buy it online! Don't just buy what is available locally and find out only later that it is not compatible.

Tools for estimating your needs

ESC, motor and battery needs to be compatible. You need to know what kind of power is needed to fly your kit and then configure a appropriate propellor, motor, ESC and battery combination to give you that power. For that, I find the software Motocalc extremely useful in estimating the thrust, current draw and flying time etc. It has a comprehensive database specifications of the different brands of motor, esc, batteries etc.It even gives you an opinion to predicting what your kit will fly like. This should give you a good picture of what to go for. That is however, just the predicted calculations, you will still need actual tools to measure the real readings from your power setup. Over time, I found the following tools quite indispensable. It would be good to invest in them, it sheds a lot of light to what kind of a power you are putting through your plane in terms of voltage, current etc and save you from storing up burned components.

Very useful tools to have:
-- Multimeter: measure voltage, current. Good to check your battery state etc
-- Clamp Meter: Works like multimeter but not as intrusive.
-- Tachometer: measure RPM, good to compare with simulated predictions.

Armed with both simulated predictions and actual measuring tools, you will be saving yourself a lot of guessings and keep wrong buys to a minimal.

Power Setup

Understand your requirements, with the simulated predictions, you should be able to single out very closely what components you would need. Say you decided that a GWS EM350 motor on a 4/2 propeller would best power your flying wing on a 2 cell lithium polymer configuration and Motocalc predicted a current draw reading of about 9.6 amp. You would need to mate this setup to a ESC rated for that draw, 15 amp for example to be safe and also a lipo 2 cell that is able to be discharged continuously at 10 amp. Experienced flyers would normally settle for slightly higher spec to give themselves some margin of safety. You may also want to consider the weight of the battery, going light is good but not to the point of needing to put weights to balance your plane to get the right CG balance.

Other considerations

There are brushless and brushed motor type to use and will need brushless and brushed ESC to work with respectively. Brushless uses stronger magnets and will typically give you more power and better efficiency for a given input and will not wear out like brushed motors do. Beginners would normally start with brushed setups to make the best out of its low cost nature and upgrade later to brushless when they are more experienced and comfortable with more powerful setups. While Brushless will cost more, you get more than just power and efficiency upgrades. There is less fuss to change the motor rotating direction with a simple switch of 2 cables (Brushed 2 cables and Brushless 3 cables). You won't need to retime a brushless for the direction it is spinning and it is somewhat cleaner without the inherent spark making nature of brushed motors. Timing is all handled by the ESC and a brushless ESC will usually give your more options to set like voltage cut off point, timing, brake action etc. Brushless will give you longer lifespan of usage to brushed setups.


Conclusion

Electric flight isn't new, and a simple google find will turn up many guides on it but it is still not uncommon to find somebody trying furiously to launch their plane in the air and asked why it wouldn't fly or why their motor keeps cutting off 5 seconds into flight. Avoid components with unknown specifications where you find yourself guessing and worrying if it will fry your esc or ruin your batteries. The key to enjoying electric flight is to understand your power requirements and acquired the right stuff to do the job. Have fun configuring!