Risk of blowing Crystalyte 20 amp

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magudaman
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Joined: Wednesday, March 14, 2007 - 10:00
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Risk of blowing Crystalyte 20 amp

I am currently running a crystalyte motor controller on 66v and have noticed on my drain brain its hitting 25 amps max and is rated for 20.I'm guessing that its not current limiting and want to know is there a big risk of blowing fets? Have people blowin these pretty easy before? The heat sink doesn't really get that hot.

abcd
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Joined: Tuesday, June 19, 2007 - 19:15
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Re: Risk of blowing Crystalyte 20 amp

Interesting, are you using a brushless or brushed controler.

Many controlers seam to use several fets to carry the 20 amps per phase.

So exactly how your using these, if its a brushless 3 phase , lets say its 20 amps, but divided by 3 , in terms of actual on time for each phase.

So the fets are only on for , 1/3 of the time, so this impacts ratings of power handeling for electical devices some what.

Then there is air temperature, the device is designed for, and overload or max starting current.

The pwm devices I believe limit current, by sensing it and then shuting it down if its over some limit, since this takes time, once 20 is reached you could be at 25 amps before it shuts down.

I thought the brain drain device could limit current by shuting down the hall effect throttle input signal.

The 25 amps before shutdown, could be part of using the 66 volts that the current rises very fast, before the device can shutdown the current is at 25 amps.

Also the tolerance of the resistance used to sense the, 20 amp limit and the other components that make up the sensing curcuit could be out of tolerance.

Anyway you might as well keep using it, since it works, for now.

You could modify the current sensing curcuit to reduce the current to lower values.

Probably not worth while since it works as is.

magudaman
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Last seen: 15 years 6 months ago
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Re: Risk of blowing Crystalyte 20 amp

Sorry I didn't say but it is the brushless controller. As I mentioned it doesn't really get hot but just warm. Only the new Drain brains do the current limiting, I have an old one. I have also heard that when using brushless controllers the phase side of the controller can be putting out a lot more amps than what is being drawn at the batteries how is this so or is it? Thanks for the information!

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