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Author Topic: Motor surges - Gain, timing and Pwh settings  (Read 6000 times)

Online Dennis Toth

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Motor surges - Gain, timing and Pwh settings
« on: November 06, 2013, 06:10:53 AM »
Guys,
Now that I have my firmware and Castle Link problems solved I started to do some run tests on my Turnegy 3542 -1000 motor with an APCE-P 9x6 prop. I started with a no load test the ESC is a Phoenix 35, set for control line, fixed rpm. I have the Gain set at 42, timing is 6, Pwh is 12. Upon startup with no load I noticed a little surging, not bad but a little. I have not had time to do the tests with the prop on.

Question - assuming it does surge with the prop load what is the order of adjustment to the settings? Do you lower gain or timing first? Could increasing Pwh to 16 reduce the surging?

Best,       DennisT

Offline Tim Wescott

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Re: Motor surges - Gain, timing and Pwh settings
« Reply #1 on: November 06, 2013, 09:58:40 AM »
I don't know what Pwh is, or just how Castle arranges their control loop.  But the behavior of the motor is going to change markedly when you put a prop on, so I wouldn't put too much energy into trying to tune it up without a prop.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Dennis Toth

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Re: Motor surges - Gain, timing and Pwh settings
« Reply #2 on: November 06, 2013, 12:03:13 PM »
Tim,
My bad, I meant PWM switching rate is set to 12 KHz. Was wondering which adjustment (gain, timing or PWM rate) has the most impact on the surging?

I agree once the prop load is on it will be different than no-load but just in case would be good information to understand.

Best,     DennisT

Offline Tim Wescott

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Re: Motor surges - Gain, timing and Pwh settings
« Reply #3 on: November 06, 2013, 02:26:51 PM »
OK -- I design stuff like this but I don't work for Castle.  So I've seen just about everything that can possibly go wrong and I'm deeply suspicious of any pie that I don't have a finger in, too boot.

And I don't even diddle with electric control line planes, so I have no direct experience.  But if Castle isn't completely mistaken or lying about what those names mean then there's only so much that the behavior can deviate from normal industrial motor drive practice.

Now that you have my disclaimer, here's what I know:

Timing and PWM frequency should mostly have an effect on the overall system efficiency and shouldn't make a bit of difference to surging.  However, if they're way wrong then they could have an effect.  Normally I would expect that setting the timing or the PWM frequency wrong would make the motor run hot, and that heat would just be Joules that went to heating up the air instead of turning a prop.  But I wouldn't expect that it'd significantly change the regulation of the speed loop, which is what the gain setting should do.  If the timing was so bad that you were actually making the motor wimpy then it could affect surging -- but it's unlikely.  Ditto PWM frequency.

Gain should have the most impact on the surging, if the gain setting and the surging are both what I think they are.  In an ideal world (i.e., one in which timing and PWM frequency never made weird things happen) then gain would be the only thing you'd have to worry about.

Stick a prop on the thing.  Increase the gain until you notice definite signs of surging, then back the gain off by a factor of two.  If their software is written the way I think it is, you should be fine.

I would look for signs of surging by grabbing the spinner of a running motor briefly with my gloved hand to slow the motor down, then letting it go as crisply as I could while listening to the sound it made as it recovered speed.  Exactly one "waa" out of it as it speeds up, or as it overspeeds and recovers, is what I would expect.  If it goes "waa waa waa", repeatedly speeding up and slowing down, then I would reduce the gain.

Needless to say, in order for that test to work you need to have the motor firmly mounted to a plane or a test stand, you need a prop and spinner on it, and if you're picky you need to use a spinner you don't care much about (if you're a lawyer you can put polishing compound on your glove, and say you meant to do that).
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Dennis Toth

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Re: Motor surges - Gain, timing and Pwh settings
« Reply #4 on: November 07, 2013, 08:11:51 AM »
Tim,
I got a chance to run the prop on test last night and with the gain set at 42, all was good, no signs of surging. I did find that the K rating on the Turnigy 3542-1000 is not exactly 1000. I was aiming for a fixed rpm of 9500 with an amp draw around 16 ish. It was necessary to lower the rpm several steps to 9300 to get the actual 9500. But once set it also had the 16.1 amp draw I was hoping for with the 9x6 APCE-P prop. Next step is to go fly and smoke test in the air.

Best,        Dennist 

Online Dennis Toth

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Re: Motor surges - Gain, timing and Pwh settings
« Reply #5 on: June 12, 2015, 11:36:55 AM »
I've been flying the old Stuka a few times this season and it was close on lap time but just a little slow (5.1 I like 4.95 for 60'C to C). I set mine up ESC for "fixed rpm" in control line mode. I use a Zetron timer set for 100% start and end with a 20 delay at power on and let the ESC control the rpm. Simple, well seems there is a way to screw this up. For the Stuka I have the timer in a recess in the bottom cowl and the "on/off" power switch tucked in the bonnet part of the cowl. Nice clean installation. I appears that there is a way to unintentionally reprogram the Zetron if one happens to push in the "push button" on the unit while picking up the ship then turning off the power.

As I said I like around 4.95 sec lap time for 60' C to C line length, since mine was a little slow I decide to bump the ESC rpm from 9500 to 9700. I did this last weekend and flew the ship. Same 5.1 lap time. I took two flights this way and it was solid at 5.1 from beginning to end. I checked the ESC setting and then tried bumping to 9900 rpm, flew the ship, same 5.1 lap time. At this point I figured either the timer was bad or the ESC was having a problem. I decided to look over the instructions for the Zetron and began to think that maybe it was somehow not set for full 100% power output. I went through the program for motor start (this is the first half of the run not "startup" power) and set it for 100% and did the same for motor end. I then checked the rpm and found that did it! It was now turning 9900 rpm as programed into the ESC. Either it wasn't set right at the very beginning or somehow got reprogram unintentionally while picking up the ship but its now fixed.

Best,         DennisT

Offline Motorman

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Re: Motor surges - Gain, timing and Pwh settings
« Reply #6 on: June 23, 2015, 11:04:14 AM »
http://stunthanger.com/smf/index.php/topic,39304.0.html If it's the edge lite you probably fixed it by going back through the settings.

MM

Online Dennis Toth

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Re: Motor surges - Gain, timing and Pwh settings
« Reply #7 on: June 23, 2015, 04:15:14 PM »
Actually, I did some additional testing and it appears the Zetron timer was set at a reduced throttle setting which started to fight the ESC "fixed rpm" set-up. I did two things to clear the problem. First I reset the ESC to default setting then went through the full set-up to the fixed rpm setting I figured I need. Then reset the Zetron to default and went through the full set-up for 20 sec delay start, full start power, full end power. I flew it and got close to the lap time I wanted (went from 5.1 to 5.0). I will make another tweak to the rpm and should be at the 4.95 lap time I like for this ship.

As a bonus, by eliminating the miss match between the Zetron and ESC the current draw dropped 1.5 amps.

Best,          DennisT


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