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Old Jul 24, 2003, 02:08 AM
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Malaysia
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What happen when one motor failed in Parallel ESC?

Hi all

In parallel setting you will have both motor(twin) sucking the amp for the same volts. Ie with 2 sp400, I will probably see something like 20A for 8 cell pack on a gunther prop.

What happen when one motor jam/seized? Will your esc fried as it will continue to drive the other motor. Essentially with one motor seize it is almost like having the esc output shorted? Am I right or lost?

Thanks.
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Old Jul 24, 2003, 04:26 AM
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Arthur Knowles's Avatar
Fallbrook, CA
Joined Oct 1998
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That depends on the short. If ths motor shorts on an open ciruit (i.e., no current) there will be no amp increase. If it shorts on a closed circuit, it'll most likely short out and poof there goes the magic smoke. But a lot depends on where the short occurs.
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Old Jul 24, 2003, 05:14 AM
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gouch's Avatar
Lake Macquarie, Aust.
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Arthur:
I assume it would be the same with one motor too?
Would the best way to stop a short frying an esc to use a fuse?
And in a twin use two fuses, one for each branch?

Cheers
Paul Just checking to see how much i've learnt here!
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Old Jul 24, 2003, 11:11 AM
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Arthur Knowles's Avatar
Fallbrook, CA
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Yes, one motor that fries can go the same way. As for protection, I'd just recommend a single fuse in the wiring harness right after the battery. In most cases, it's best to deadstick a twin rather than try to fly on one engine (exceptions are those with the engine/motor close to the center line).
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Old Jul 24, 2003, 11:43 AM
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Paul Penney's Avatar
Ancaster, Ontario, Canada
Joined Nov 2000
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Arthur,

After the battery? I dont like the idea of some large twin foating out of control on a field or a public area. It would be best to put the fuse(s) on the motor side. Having two would even tell you what motor you blew, not less possibly save your airframe.
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Old Jul 24, 2003, 12:31 PM
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N. Staffs, UK
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A fuse between battery and ESC is a really bad idea if you are using BEC to drive your Rx and servos. Fuse goes, no power to receiver, no control. You're just a spectator waiting for the crash.

Of course you can only fuse between ESC and motor with brushed motors. It doesn't work with brushless, too many wires.

Personally I don't like fuses. Why put something in your plane who's only purpose in life is to break ? BTW fuses will very rarely blow quickly enough to save an ESC.

Steve
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Old Jul 24, 2003, 04:13 PM
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Fallbrook, CA
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RE: BEC and Battery.

Yep, absolutely correct! I kinda forgot that most of my twins always used a small 225 mah Rx battery.
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Old Jul 24, 2003, 08:28 PM
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So does this means, I have no good answer for it and it is an acceptable risk in twin?

For 2 sp400/480 twin, parallel, is 30A is a bit too risky?
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Old Jul 25, 2003, 02:59 AM
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East Anglia, UK
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IME the ESC will fry before the fuse goes...the fuse is proably a good idea to stop teh pack catching fire on a short - so....

- fuse the battery way above the expected max current, but below the point at which teh pack catches fire - say 50A.

- I would fuse teh motors as one - before the Y split - so that if one motortt ges, they both go.

I'd say the danger of a dead stick is less than one motor flat out and teh other stopped

Conversely, all those fuses will soak up power. I'd say **** it and run unfused. If the ESC fries and you end up with no control so be it. At least the ESC will (normally) cut power to the motors once it goes up in smoke.
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