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TOPIC: Constraints for the EPPG Brushless Motor

Constraints for the EPPG Brushless Motor 3 weeks 3 days ago #610

  • Madars
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I have just found www.g-air.eu , www.e-ppg.com , alienpowersystem.com and I am very pleased that there are DIY side also for electric paragliding community out there!
I have the DIY electric PPG in mind for some time and have done deep online search in this field. I am well aware of latest tech in the field of electric propulsion systems for drones, UAVs, RC hobby in general.

What surprises me is that there are still a visible lack for direct drive pancake/ring type (large diameter vs axial length ratio) multi-pole, low speed (kv) and high torque permanent magnet brushless motors (PM BLDC) out there!
It is well known that drone industry pushed the development of various types of PM BLDCs and that high speed, low pole number motors are and will be mandatory in this field due to the drone flight characteristics and constraints.

Though, in the case of slow flying machines (where quick motor response as a result of small prop and high speed is not that necessary) like in motorized paragliding, where the nominal cruise speed is about 10 m/s (mainly defined by wing characteristics), to have low speed, high torque direct drive BLDC is crucial and so far it is almost impossible to buy such a motor for DIY EPPG purposes in reasonable price range.

I am aware of three very spectacular projects all of which are designed for the particular purpose: ELECTRIC POWERED PARAGLIDING!

Spanish company www.paracell-products.com
Czech company www.e-glider.com
Swiss company www.flymanilla.com producing motor models flytec HPD 10 and 13 (more about it here and price list of all components here ).

The point is that all of these motor manufacturers do offer an excellent solution for EPPG, though it is WAY overpriced and offered as a ready to fly solution for go-green’ers/ ‘’planet earth savers’’ and mainly rich people who can afford spending 8k to 10k (or more) just as those who spend 2 times as much for the electric vehicle nowadays. Those companies are going to offer by no means high quality, high-end product to make profit. This is not what DIY people are looking for.

As we know, there are plenty of DIY communities around in these days and forums are full of them willing to build things themselves, for instance www.rcgroups.com for all that is RC and endless-sphere.com all about e-bikes. Though, not all of things can be completely DIY and electric motors are one of them.
I am aware of complexity of CAD/FEM and CAM design and optimization processes and testing to prototype an electrical machine. To get it truly high performance, it is very time consuming and costly process while in prototype stage and therefore it purely belongs to science (R&D), heavy manufacturing and business world rather than DIY world (however, there are highly skilled and knowledgeable, experienced people who go DIY even in this field, see Iulian from Youtube ).
I came up so far that the most viable solution in hobby level electric motor industry is CHINA production. Unless Chinese companies are not mass producing machine models meeting previously mentioned constraints, the best way to go, in my opinion, is using indirect (belt) drive systems observed here in forum.
It is clearly noticeable that China produces all and it basically depends on mainstream demand (like there is a great demand for drone type BLDCs and therefore we can get them cheaply and all over the web online).

I would like to clearly state that every high performance electrical machine has its own very specific APPLICATION. There can be two visually similar machines that are technically very different and and have little to do with each other. Therefore it is crucial to clearly count all the main constraints for the electrical machine that is designed for the specific and particular application - electric powered paraglider propulsion system.

The motor for electric powered paraglider (EPPG) propulsion system has to meet the following constraints:

* Direct drive (no gearboxes, no belt drives or whatever mechanical power transmission parts);
* 3 phase AC supply (inverted DC battery power source);
* compatible with RC hobby stock speed controllers (ECS) or custom affordable ESC;
* Permanent magnet (PM) excitation (NdFeB, high temperature resistant grade);
* Low shaft speed n = 2300...2500 rpm;
* low speed (velocity) constant kv = 30...50 rpm/V;
* Large outer diameter vs. axial length (about 6:1);
* multipole configuration (more than 24 poles);
* Electrical power in range of 15 to 18 kW;
* High torque to spin large diameter (D110 to D130 cm) propeller used in PPG, producing 50 to 70 kg of thrust) in nominal working regime (not burst mode for up to some minutes like those high kv drone BLDCs);
* high specific power (at least 4 kW/kg) - get used, guys. The specific parameters are the most representing when comparing different kind of machines; Specific power is one of the main in aviation because the whole thing needs to stay airborne!
* Air or water cooling. Usually forced air cooling by centrifugal ventilator designed in the rotor; For enclosed system the water cooling is the way to go but due to its complexity, let’s focus on air cooling;
*Good price/performance ratio (20...30 Eur/kW). Yes! This is almost the main constraint after all. Unless the machine enters in this price tag, DIY’ers won’t be able to go electric and direct drive!

I would like to hear your thoughts and view about the present situation in the EPPG motor availability!
The following user(s) said Thank You: Wannabeaflyer

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Last Edit: by Madars.
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