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Old 08-21-2005, 08:40 PM   #1
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Default ESC FET question.

Hi, I have just been recently surfing the web, looking at ESCs, and I just stubbled upon the Atsushi Hara Twister 2.1. Is that ESC any good? (hehe want to get one. it looks so tricked. Is $160USD a good price for it?)

So anyways, I continued to read, and it said: (under its specifications)
Maximum electric current: 3120A (FET Spec)
Continuing electric current: 780A (FET Spec)

I am wondering, what does this "780A" mean? 780 amps? I heard Mod motors draw 40Amps, and that's about its maximum? So why do we need 780 amps?

Why is the amp rating on the FET Spec so high? And the Max current is even more crazy? 3120A?
How does anything that weighs 18.8g withstand 3120A of current?? I realize the voltage is low, but that's still a pretty big number!

If anyone can dumb it down and explain it to newbies like myself, that would be awesome! Thanks in advance!
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Old 08-22-2005, 04:27 AM   #2
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1. If you gear to dump 3800 mAh cells in 5 minutes the average current is 45 amps. (I'm all for 10 minute mains, and 15 minutes in 19 turn. More fun, longer lasting and cheaper equipment). Half the time (don't argue) is spent braking so when you're accelerating the car is using 90 Amps average, stalled motor and accelerating from dead stop draws lot more.
2. Having more capacity for current than you're actually using keeps the FETs cooler. Cooler FETs reduce the need for heat sinks so you get smaller and lighter ESC.
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Old 08-22-2005, 04:31 AM   #3
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IMHO Fet specs aren't interesting for the performance of an ESC. There's more to it than just the Fet's. There are more components in there that make a difference.
In this case, it's a good thing to be a follower. Just run what the fast guys run.
The Ko VFS is a very good ESC, that has won a lot of big races.
Also have a look at the top end ESC's of among others LRP, Novak, Robitronic and Nosram.
Choose the one you like most, and is best supported in your area.
If you're a beginner, ask around on the track if anyone has a good used ESC that they're willing to part from. You don't need the latest equipment to win.
I personally still use my trusty old Novak Cyclone. Its performance is still up there with all newer ESC's, and I bought it used two years ago.
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Old 08-22-2005, 04:33 AM   #4
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The quoted figures are often just the specs of the actual FETs themselves - not the amp rating of the whole esc, as obviously other current passing components would burn up well before the max FET rating was achieved.
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Old 08-22-2005, 11:51 AM   #5
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hmm... so can I interpret this as... the FET specs are used to basically indicate the relative quality of the FETs being used? Its a show off number which does not provide much physical meaning but allows one ESC's FETs to be compared with another?
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