On this brief tutorial, we’ll clarify the right way to rewind brushless motor broken by windings burnout because of the overload, brief circuit, or sudden motor blocking at full velocity. It’s not difficult once you get the complete concept, and it may prevent loads of time (no ready for brand spanking new motors to be delivered) and cash (sure, you are able to do it by yourself).
Commonest motor failure
There are a number of methods to wreck brushless motor windings:
- & Overload
- Overheating because of inadequate cooling
- Vibration and mechanical injury of inner winding juction and energy provide wires
Motor overload is the most typical reason for stator core burnout. For those who load your craft greater than the mass propellers can raise, the motor will warmth up in a short time which can trigger inner isolation (polish, enamel) melting.
As quickly because the enamel is melted, there’s a brief circuit contained in the winding and that causes wire melting and motor destruction. Motor overheating can occur quite a bit if the rotor is poorly designed and the airflow which cools windings is inadequate for correct stator inner core cooling.
Mechanical injury and powerful vibrations can result in a break within the connection of a wire which powers the motor and stator inner core wires.
elements of a brushless motors
When the motor is armed, the rotor is locked to the stator with a C-clip key which secures the shaft - it stops the rotor from the flying out of the motor bearing, together with the propeller and the whole lot related to the shaft.
The stator is product of tiny metallic sheets and it’s protected by industrial varnish which is immune to excessive temperatures, and often olive-green. It’s product of sheets moderately than one strong piece of metallic as a result of it creates a extra environment friendly magnetic area. Just some windings round each stator tooth creates a magnetic area managed by ESC.
In three-phase motors, the variety of stator poles have to be divisible by three.
For instance, we’ll take BARD Lil' Floaters with 9 motor tooth. Nevertheless, the variety of magnets on the motor can differ. 11xxx, 12xxx, and so on motor sizes sometimes have 12 magnets and 9 stator poles. The marking we use (for this instance) is 9N12P.
Three-phase motors have three motor phases they usually’re being related to hurry controller (ESC) with three wires. The coils are manufactured from three lengthy wires, winded round stator tooth in a particular approach. There are two methods to try this:
Wye (Star) termination: three beginning factors of wires make a impartial spot of every of three coils. In motors we use in RC world, this level is protected by heat-shrinking tube and it’s contained in the motor, often underneath stator tooth. In Delta termination, there’s no bodily impartial spot.
Delta terminated motor is rotated roughly 1.eight occasions quicker than Wye terminated motor, whereas the Delta terminated motor has 1.eight occasions greater torque. It’s potential to transform Wye into Delta and vice versa, if wanted (velocity or energy).
Brushless Motor Disassembly
For a begin, that you must take away the C-clip key which holds the rotor shaft contained in the stator bearing and isn't permitting it to develop into separated whereas the motor is armed.&
Some declare that retaining the rotor outdoors the stator for an extended time interval is damaging for magnets as a result of they begin to lose their magnetization. Nevertheless, no scientific concept proves or disproves this.
Subsequent, you take away the rotor from the stator. It’s advisable to retailer the C-clip someplace safe- it’s fairly straightforward to lose it.
After that, you take away the winding half which represents the impartial spot and untangle it.
On this instance (and each different motor of this sort), it’s greatest to start out unwinding from that time as a result of it’s the simplest to rely the windings.
It’s necessary to rely them, if potential, as a result of we’ll want that info for winding again. If not potential (burnt wires break simply and also you’ll have a tough time separating and counting them), we will all the time e mail the producer’s buyer care and ask for the right details about the wire thickness and variety of windings.
The wire must be extracted very rigorously; you should keep away from damaging industrial varnish on the stator tooth - it protects core wires from the brief circuit. It’s advisable to make use of plastic instruments for this. Varnish residue must be cleaned correctly, together with the filth and soot staining. If the economic varnish is broken, you must use acrylic varnish or one other temperature-resistant coating on the broken space.
After the cleansing, you can begin with first windings.
Brushless Motor Winding
When repairing the motor, it’s necessary to decide on the right sort of wire. For motors, we use polished enamel wire with larger temperature isolation melting coefficient - enamel has been confirmed to be optimum for this.
On wires.co.uk & you'll find principally all industrial wires wanted for this job. Costs are low, supply quick, wire is high-quality and might be ordered in multiple color. 50g wire (and sure, they're metric, even in UK ) spool is sufficient for dozens of motors so it’s greatest to order that one.
The worth vary is £2-£three, relying on the wire thickness. For this tutorial, we’ll use zero.18mm wire. It’s value mentioning the wire thickness consists of the coating thickness as well- meaning the efficient thickness of a wire is a bit decrease. Thickness marking signifies isolation thickness as properly (for talked about web site solely). In any case, it’s all the time a good suggestion to take a look at the catalog offered by the web site.
This motor has the most typical winding scheme- ABCABCABC. You might want to wind the windings very rigorously, with first winding on the underside shifting upwards to the highest of the stator tooth.
Once you rely the windings (the reference must be the unique motor), you skip two tooth and wind the subsequent one. When that one is completed, skip two tooth and wind the subsequent one, and once more, skip two and wind the subsequent one as final of the A part is completed. Do the identical for the part B and C.
Sometimes, stator producers mark some tooth with dots. You should use them as a place to begin. First, you discover a place to begin and wind the right variety of windings.
For instance, we’ll use 11 windings. It's worthwhile to distinguish the beginning and the top of the wire so we don’t get misplaced in them. In my case, the beginning of the wire is all the time longer than the top - it’s a good way to know which wires to hitch right into a impartial level.
When the primary three tooth on part A are sorted, you progress on to the subsequent part from the subsequent first tooth clock-wise course. It’s additionally essential the place do wires finish as a result of the interior wire have to be related to the exterior wire.&
It's essential watch out - because the mount sample of the motor is already outlined, when you miss the spot, the wire exit level gained’t match the carbon body arm and also you’ll have to redo the entire motor.
After you end part two (B), you progress on to part three (C) the identical means you probably did earlier than with part A and B.
Subsequent, you join the impartial spot (termination level) and separate wires with all three phases and transfer the wires away.
For those who obtained so far, congrats, the important a part of the method is completed. You want to take a look at each tooth, examine if any wire is crossing the tooth line (if it does, transfer it barely to the centre).
This hyperlink: http://www.bavaria-direct.co.za/scheme/widespread/#prettyPhotois an excellent supply of details about different patterns. The scheme for this instance, 11xxx, 12xxx, and others is identical because the CD-ROM sample within the hyperlink above.
Testing Brushless Motor
Whenever you’re completed with winding the wire, it’s time for testing. First, that you must solder the termination level wires and ensure all three wire ends are efficiently related. To try this, it's worthwhile to drench the tip of the soldering iron with the solder till you get a soldering blob. You pull the wires via the blob till the enamel has melted and wires are soldered collectively.
Subsequent, you join three ends to ESC (or, on a flight controller, AIO, as proven on this instance). Wires are, at that time, not shielded from the vibration and different mechanical injury so you must be very cautious when dealing with them. You might want to examine if there’s a brief circuit and punctiliously put within the rotor. Termination level could be shortened moreover if wanted.
In your favorite flight controller configuration software program (Betafllight and so forth.), you possibly can activate the motor to see if it really works. If, when the battery is related, you hear ESC’s initialization “melody”, you’re heading in the right direction. You activate the motor and pay attention for any odd sounds, vibrations and so on. On this photograph the whole lot’s alright. It's also possible to attempt to check the motor with full energy to see if there’s overheating.
After you made positive every thing is okay with the motor, you cowl the windings with a really skinny layer of clear nail polish to guard them from vibration and motion. Then, you shorten the wires and put together them for connecting with the primary wires. Watch out when slicing the wires- in case you reduce them too brief, you’ll need to undergo the entire course of again- which incorporates eradicating recent nail polish you simply utilized.
You solder all wires collectively so the smaller ones don’t stick out; solder joint have to be parallel and roughly 2mm size. This manner of soldering prevents vibrations from breaking the wire connection.
The impartial termination level ought to be shortened as a lot as potential (that you must watch out to not unwind it within the course of). Warmth-shrinking tube will shield the termination level and three major wires. The diameter must be the smallest as possible- too extensive one can get caught within the rotor and that definitely must be prevented.
After warming up the heat-shrinking tube with a hot-air gun, when the tube is the tightest round wires, bend the termination level and tuck it between the stator and motor base so it doesn’t hit the rotor magnets.
Additionally, that you must examine if unprotected wires are touching the stator tooth and modify the wire pressure if that’s the case. When the fixation is completed, cowl them with a skinny layer of nail polish and let dry.
When the nail polish is lastly dry, and the wires are fixated on the underside of the stator and motor base, you’ll shield them with a heat-shrinking tube. Watch out to not decide too large tube- when shrunk, it shouldn’t contact the rotor. After you ensure all wires are so as, you possibly can assemble the motor.
Don’t overlook to place the C-clip to the underside of the shaft earlier than you check the motor.
When the motor is assembled, together with C-clip on the underside of the shaft, you'll be able to solder the wires to the FC and attempt to activate the motor. You additionally have to verify the sounds the motor makes- be certain that to offer a number of speeds a attempt to wires isolation isn't touching the rotor.&
In essence, motor winding isn’t as difficult because it appears. Till the winding method is perfected, you’ll spend a whole lot of meters of wire however, when you get it, it can go seamlessly. Follow makes good. When you’re having points with separating the stator from the motor (that may typically be problematic), you’ll even have hassle with winding tooth the closest to the underside of the bottom. The probabilities of aesthetically pleasing windings are fairly low.
An important parameters talked about are: the variety of windings (you don’t need to have a special variety of windings on tooth and you should be sure that they’re all the identical) and the thickness of the wire (too skinny means faster overheating and too thick one means not sufficient area for desired quantity od windings- it is advisable to stability the 2).
When your motor burns out and bearings and the rotor appear wonderful, grasp on to it and repair it. You may fail the primary time, you may rely it fallacious, however whenever you wind your first motor and your craft efficiently flies, you’ll by no means throw away burnt-out motor ever once more.
& Writer: Davor Kustec