Kelly Brushless Setup Problems

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Trogdor!
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Kelly Brushless Setup Problems

Post by Trogdor! »

I've been converting an old Afron cherrypicker to electric as documented over in the Technical and Conversion forum, and documented in my build blog here:
http://e-afron.blogspot.com/

I'm using a Mars 3001 brushless motor on each wheel in a skid-steer arrangement driven by Kelly 48v 300A controllers with joystick control, but my bench testing has shown that the motor randomly stalls, particularly when moving into reverse. I've got a video of my bench test here (the stalling is shown at 1:25):
http://www.youtube.com/watch?v=TAz1NX5dgF4

The one thing I'm going to try is using thicker wire between the controller and motor, but I'm now wondering if I chose the wrong power system? The machine will weigh close to a tonne and will need a lot of torque at low speed when manoeuvring. Is this brushless setup the best choice for this application?

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Kelly Brushless Setup Problems

Post by Electrocycle »

The brushless motors and controllers should handle the loads fine.
I've used a very similar setup in a motorcycle before.

There must be something wrong with the setup to cause that issue.
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Kelly Brushless Setup Problems

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Electrocycle wrote: The brushless motors and controllers should handle the loads fine.
I've used a very similar setup in a motorcycle before.

There must be something wrong with the setup to cause that issue.


The fact that sometimes can get the thing to unjam by winding up the throttle would not be a good attribute for a vehicle as it'd be lurching off at high speed. However, assuming more throttle = more volts, perhaps it is just a voltage-drop issue?
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Kelly Brushless Setup Problems

Post by Electrocycle »

if it's all working 100% it should be smooth and seamless in forward or reverse.
The brushless motors do sometimes get a bit "coggy" when starting from low speeds with high load and power, but I never found it to be a problem.

It should still be able to put out full torque on start up without locking up.
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Kelly Brushless Setup Problems

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Electrocycle wrote: if it's all working 100% it should be smooth and seamless in forward or reverse.


That's what I was expecting, but it's *much* noisier in reverse, and draws almost 3 times the current. If you get a moment I'd suggest watching the youtube video - you'll hear the difference when it's running backwards.

The first thing I'll try is thicker wires to the motor. I have some 4G cable at hand, but I'm thinking of getting some 2G just to make sure it isn't a voltage-drop issue.
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Post by Electrocycle »

with no load on it there shouldn't be a voltage drop issue.
It should also draw the same current in both directions.

In my old bike I was running the motor backwards the whole time :)
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Kelly Brushless Setup Problems

Post by Trogdor! »

Electrocycle wrote: with no load on it there shouldn't be a voltage drop issue.
It should also draw the same current in both directions.

In my old bike I was running the motor backwards the whole time :)


That was my thinking, which is why I thought I'd be fine using light gauge wire while doing bench tests, but when the motor stalls, the phase current climbs to 200A making me think there could be a problem with voltage drop.

I'll have to experiment with running it in reverse by swapping motor wires rather than using the joystick, in case it's the firmware that makes for the rough running in reverse. I assume if I swap 2 wires at the motor, I also need to swap 2 hall effect wires? I guess I'd know soon enough if I do Image
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Kelly Brushless Setup Problems

Post by Tritium_James »

The wire gauge shouldn't be a problem.

From the video, it sounds to me like the hall sensors aren't lined up with the phases properly - this is why it is different in forwards vs reverse. Is it possible to adjust the alignment of the hall sensors? eg are they on a slotted PCB that can be rotated radially on its mounting hardware by a degree or two?
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Post by Trogdor! »

Ahem.

Well, it turns out these aren't the Worst Motors in the World after all, and that despite me thinking that I'd traversed the set of permutations of phase and sensor connections, turns out I hadn't.

Surprisingly, with the motor and hall sensor connections correct, the motor runs smoothly and quietly in both directions, drawing nearly identical current and never stalls.

Thanks for the comments and suggestions - I probably would have been whinging to Kelly Controllers by now and have ended up looking like an even greater idiot :)
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Post by Electrocycle »

aha, good stuff :)

Won't be long till you have the thing driving around!
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Kelly Brushless Setup Problems

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Electrocycle wrote:Won't be long till you have the thing driving around!


I was in a bit of a panic as pruning has started, the netting needs to be tied up and this machine needs to get working. I thought for a while there that I'd made the wrong choice in drive setup and there'd be a long delay finding a working solution, but now it's sorted, it's just a matter of mounting the other motor and bolting the lot back onto the chassis Image
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Kelly Brushless Setup Problems

Post by Electrocycle »

good luck with it :)
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