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Author Topic: Rating of components  (Read 1445 times)

tobyker

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Rating of components
« on: February 28, 2016, 09:47:51 AM »

I have a little brushless motor which apparently needs a 60A ESC. I hope to run it on a NIMH 6-cell pack or maybe a 2c Lipo. I want to use microwitches to reverse but all the ones I can find are only rated at 2 or 3A but for 250V. Does this mean they can take 750 Watts before they let all the smoke out, so they can take more amps at a lower voltage?
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petermun

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Re: Rating of components
« Reply #1 on: February 28, 2016, 02:12:09 PM »

Not an answer to your question, but 15 Amp microswitches are available.   Pete
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inertia

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Re: Rating of components
« Reply #2 on: February 28, 2016, 02:26:53 PM »

Toby
In a word, no. In fact switches are rated at less than their VAC value for DC, mainly due to the fact that DC inductive loads can and do create arcs across the contacts when opening and closing. These will pit and eventually destroy the contacts. You can obtain a 25A SPST microswitch from Farnell for around five pounds, but it may not last for long. http://uk.farnell.com/honeywell-s-c/v7-1z29e9/microswitch-pin-spst-no-250vac/dp/1796582
That said, I wonder if your motor will actually require anything like a 60A ESC. You could always measure the current and then consider the problem again. All in all, I'd recommend buying a speed controller that will do forward and reverse.
DM
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tobyker

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Re: Rating of components
« Reply #3 on: February 28, 2016, 06:16:44 PM »

Thank you very much. What would we do without such expert advice - I suspect there would be a lot more smoke about.
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essex2visuvesi

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Re: Rating of components
« Reply #4 on: February 28, 2016, 07:18:58 PM »

Just noticed this is a brushless motor
You will need a brushless ESC with reverse
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andrewh

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Re: Rating of components
« Reply #5 on: February 29, 2016, 02:16:54 AM »

Hi, Tobyker


You have  wise advice and true!


I have frequently reversed my small brushlesses with microswitches (since I had only aircraft ESCs)
A little thought sorts out what you are switching -
you will be changing over two of the three motor leads :-)
AND you will be doing this when the motor is stopped (closed throttle)
So the current  = nil
and the voltage = nil
at the time of switching
So the microswitches have to carry the full speed current - but should never have to break it


So go ahead if you have to, but even I, a scotsman, now consider reversing ESCs good value


Tell us what the motor is , and what it is driving, and we may be able to point you at a happy reversing brushless ESC


andrew

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