10kW BLDC outrunner drive

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Jeremy
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Postby Jeremy » Tue May 26, 2009 2:02 pm

Hi Bob,

The sensors I used are the normal latching ones used in lots of electric bike motors, part number Honeywell SS411A.

They are readily available from RS Components, here: http://uk.rs-online.com/web/search/sear ... R=181-1463

They need a pull up resistor, as they have an open collector output, but, being a latching type, are relatively immune to noise. I've found that they almost fit in the motor stator slots, all that is needed is a bit of very careful machining to widen the slot slightly, taking great care not to touch the windings!

Out of interest, I've now stripped one of my motors and am in the process of rewinding it to get a lower kV. I'll post results once I get them.

Jeremy

bobc
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Postby bobc » Tue May 26, 2009 8:55 pm

Thanks Jeremy,
BTW, I suspect that switching from delta to star might slip a 30degree(electrical not mechanical) factor into the mmf which might make it difficult to get best performance with a fixed sensor position, any thoughts?
I guess 30degrees electrical doesn't amount to a great deal & will enable one to engineer a modicum of lead into the commutation for better high speed performance....??
cheers
Bob

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Jeremy
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Postby Jeremy » Wed May 27, 2009 6:18 am

The delta to star mod does introduce a 30 deg electrical shift, as you say, but in practice this doesn't seem to have a noticeable effect. You can clearly see it on the 'scope, but I've not spotted any obvious ill effects caused by it (yet). The controller I'm using auto-detects for 60 degree/120 degree sensor configurations in software, so whether or not it's capable of compensating for the small shift caused by the sub-optimal placement of the sensors I don't know. I guess I need to look and see if it has some form of back EMF sensing as well as Hall sensing, I suspect it doesn't, though.

This $22 e-bike controller it's pretty good, really. I've changed the output FETs to IRFB3077s, so it's good for up to around 65 volts or so, with phase currents of up to about 100A or so, plus it now has reduced losses from the low Rdson of these FETs. I've managed to acquire the programming software for this controller, which allows things like the current limit, phase current, cruise control settings, electric brake cut-off settings, regeneration control, throttle settings, maximum reverse speed and low voltage cut off to be set. All told, it's pretty good value. It uses the Infineon XC846 microcontroller, which is electrically similar to the XC864 (data on the latter is available on the Infineon web site).

Jeremy

bobc
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Location: Knutsford

Postby bobc » Thu May 28, 2009 7:46 pm

Just got my motor turning with the external optos - always a good moment! I was supplying it with 1amp, current controlled, & this is an 80A motor, plus I think I only had 2.5 phases working right... but it should all be downhill now.
My drive PCB is a single sided board made by a mate (in his kitchen), in retrospect this was a mistake as I've spent far too much time fixing board faults & the lack of solder resist makes using the small SMDs a bit of a lottery. Still a few hundred rpm of sustained rotation makes me feel a lot better - just need another factor of a hundred in current now....... ;^)
Bob

bobc
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Postby bobc » Fri May 29, 2009 9:24 pm

here's the motor going
Image
and the inverter topside (you can't see the SMD stuff)
Image

JimC
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Postby JimC » Sun May 31, 2009 1:57 pm

It's good to see your making progress. How much power do you need from your motor?

I am going to be testing the Scorpion HK-4025-630KV. 4 of them should give me about 10kW. These motors are rated as 2k7 W continuous power. They also have a 4035 model rated as 3k5 W cont.

http://www.micronradiocontrol.co.uk/scorpion_hk40.html

If you are intersted in checking them out.

JimC

bobc
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Location: Knutsford

Postby bobc » Sun May 31, 2009 10:54 pm

I'm aiming to make a set of 10kW drives for this project, that's 4 of the motors above on a single shaft. As Jeremy said in the other thread, the outrunners seem to have the best mix of cost and manageable rpm!
His comment about the bearings is interesting: if that's real then I should replace all the bearings as soon as I get the motors...!!
I have had no problems with these motors yet but I've not had high power through 'em yet....
There remains the question about their continuous rating: I'll be buildint the amps up over the next few weeks.... we'll see!

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Jeremy
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Postby Jeremy » Mon Jun 01, 2009 6:33 am

Bob,

The problems I had with the bearings were only noticed when I took a motor apart to fit the Hall sensors. On one of my TowerPro motors, the big bearing was locked solid, as was one of the two small bearings. Further investigation revealed that these bearings were filled with what seems to be epoxy resin, probably from overspill when the windings were coated. The motor shaft was actually spinning in the inner race of these bearings, which was a bit worrying.

I stripped my other TowerPro motor last week, to rewind it for a lower Kv, and similarly found one of the small bearings filled with resin. I've split one of the resin filled ball races apart and found that it didn't have any sign of lubricant in it, which explains why the resin stuck so well and may explain why so many of these cheaper outrunners seem to have a reputation for early bearing failure in the RC world.

I replaced the bearings in my motors with standard SKF ones, not too expensive and only a few minutes work. As a result, the one motor I have running at the moment is definitely much smoother.

BTW, I should have a one of these motors running with a Kv of 60 (in star configuration) soon. This one is destined for direct drive on a small electric boat propulsion system.



Jim.

As I mentioned on the other thread, you may want to re-think your motor choice. The high Kv is going to make a reduction drive challenging, as that motor will be spinning at more than 28,000 rpm at full power. The TowerPro 5330-10t motors that Bob and I are experimenting with have a much lower Kv of 215, or 124 if re-wired from delta to star.

Jeremy

bobc
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Postby bobc » Mon Jun 01, 2009 8:02 pm

I really appreciate your continued help Jeremy - that could have been an expensive thing to find out the hard way!
This is the solder side of the board; it's just a bit of logic, gate drives and a switchmode chip. I've steered clear of micros because those projects can acquire a life of their own.... this is a nice robust simple system that ought to do what I want. I'll be using a CT to get feedback for the current mode switcher. The tracks will all be beefed up when I start to put proper amps through 'em!
Image


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