burnineyes

iTrader: (17)

I took that from a post by Joe Ford of Castle Creations, speaking of the original Mamba Max on another forum. I am far from an expert or an EE, so my understanding is very incomplete.
I did not think the MOSFETs switched between the phases of the brushless motor, but only controlled the PWM to each phase. I could be way off, so if you know better please inform me.

kufman

iTrader: (6)

The FETs are divided up into groups of 6 to form a 3 phase bridge. They do PWM and switch between the phases in some sense. Even when you are at full throttle, they are still switching. They never go to 100% on like the old brushed controllers did. At the very least, they still have to turn on and off a few times per rotation. This switching would be slower than the PWM frequency, but still represents switching.

I don't personally use EPA to soften up a setup, but I know many people who do and it seems to work ok.

R40Victim

iTrader: (1)

If reducing the EPA hurts an ESC then why do we have throttle at all? That would mean every time you didn't use full throttle, you are hurting your equipment. So those of us on smaller tracks are damaging our equipment? That's BOGUS, a MYTH and anyone with half a brain knows it.

nashvillecactus

iTrader: (3)

Just to set up a hypothetical, but realistic situation, let's say my b4.1 with a 10.5 turn motor is good for 25mph with a 7.8 final drive ratio (27 tooth pinion, 81 tooth spur). Let's say that the rear tires have a diameter of 3.25", which would give them a circumference of about 10.2". So in order for the car to be doing 25 miles per hour, if you convert miles per hour to inches per minute, that would be about 26400 inches per minute, which would mean the tires were spinning about 2587 rpm. So the motor would be spinning just over 20K rpm at top speed, which certainly seems plausible. So that would mean that the phase would be switching 3 times each rotation, so 60K times per minute, which would be about 1Khz. (correct my math if I missed something)

So what is the PWM frequency?

burnineyes

iTrader: (17)

I dont think anyone has said it is hurting your equipment, except maybe a few manufacturers who wanted you to buy another motor after blowing your first paycheck on a 9000kv for your Slash. (not you in particular) The idea is that everything is at it's most efficient when at full throttle and it can, in some cases, cause more heat.

R40Victim

iTrader: (1)

My goal isn't to single anyone out, but to shoot down the argument that having throttle control is "bad" for an ESC. I think you are right though, the manufacturers would love nothing more than to blame a part failure on you, so you have to buy another, rather than having it replaced under warranty. This reminds me of the "Ripple Current" excuse.

Jstall7543

iTrader: (2)

Ya, I know he was talking about EPA, I even mention EPA in my reply but then I let him in on a racing speed secret that's so much better. I'd rather limit the current thru my finger so it's there when I need it. Expo allows me to do this.

xxfile

My finger seems to be either in full throttle or at neutral...LOL rarely ever on the brakes...
Thats why i limit performance with throttle %age. having that full throttle there when i need it is beyond my trigger fingers ability and just gets me in trouble.
this is only necessary, of course ,when you have something that is grossly overpowered or the track conditions are especially slippery