Quote:
Originally Posted by Bob Novak
lutach and all,
The part number that we are using in our top of the line ESC is the Vishay SiE802DF which has a Ta=42.7amps and a maximum power dissipation of 125W @25C and 80W @70C. Now the On Semiconductor NTMFS4933N Equivalent spec is Ta=52amps but its maximum power dissipation is only 104W @ 25C and no spec given for 70 C. Power dissipation is very important as this determines how fast the heat gets out of the package. A couple of days ago I ran tests on five ESC's. The GTB, Kinetic, Tekin RS pro, LRP SPX and the Mamba Max Pro. The set up was as follows. Novak 8.5 turn motor driving a 6X5 propeler with all wires on each ESC the same length and size being powered by a 0-8Volt 0-350 amp power supply with no ESC electronic timing advance. The only variable were the ESC's. Here are the results at 7.5 Volt input.
Mamba Max Pro 50amps @ 11800 rpm 236 rpm/amp 31.47 rpm/watt
Novak GTB 49amps @ 11800 rpm 241 rpm/amp 32.11 rpm/watt
Novak Kinetic 48amps @ 11700 rpm 244 rpm/amp 32.50 rpm/watt
Tekin RS pro 51amps @ 11900 rpm 233 rpm/amp 31.11 rpm/watt
LRP SPX 51amps @ 12000 rpm 235 rpm/amp 31.37rpm/watt.
Now as you can see everything is about as equal as can be. This tells me that all the ESC's also have the same internal impedance regardless of how many mosfets are used. I did not have time to do a longer time at a constant load for temp rises but I suspect that this will come down to how well ALL of the mosfets are heat sinked to the outside world.
We have been discussing this max current Spec for quite some time now. We were forced into these years ago by the ridiculous claims that some ESC manufacturers were using for their max current. At that time we decided to use the Mosfet Manufacturers published max current speck at 25C as our published spec. I agree that this still is not the real world Spec but you would be surprised how many people out there still believe that if one ESC will handle 150 amps and another handles 1500 amps they will buy the later. Getting all the manufacturers to agree on one type of test for this spec would be quite the challenge and with all the overseas manufacturers getting involved it would probably be impossible to enforce.
All you tech fans out there have a great Thanksgiving.
Bob Novak
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Bob,
Nice information. So the kinetic can have let say a max continuous current of 128A or round it out to 130A. Now, since the Kinetic is not rated for higher then 2S lipos, why not use the SIE874DF which has a Ta of 52A? As for getting manufacturers to agree with a standard rating system, why not start with Novak, Castle and Tekin? If others want to get the respect afterwards, they can follow suit, but the only ones who needs to have a better rating would be the following: Futaba, Ko Propo and LRP. Thank you for coming in and posting this info by the way and my daughter and I would like to wish you, your family and the Novak crew a Happy Thanksgiving.
Regards,
Luciano.
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