sedanaddict

I ran a 6 turn in my xxx-s on a tight carpet track and after 2-3 minutes the speedo would shut down for a few seconds and come back on. i would run for 2 or 3 more laps and it would do it again. at first i thought i had a hung brush but they seemed ok. my gearing was ok, the motor wasn't abnormally hot but the speedo temp was 165. does the zero extreme have a thermal fail safe? the only thing that i did that might have contributed to the problem was i ran the factory preset for stock motors which gives the motor more punch which believe me, you don't need with a six turn! has anyone else had problems with low turn motors with this speedo?
mike lindsay

MattW

Not sure if it's got a thermal shut down, but it sure sounds like it. You are going to get it real hot with stock style settings. Suspect with some more "sympathetic" settings it might be ok. I have only been down as far as 8 turn and haven't had any problems with mine.

Rowdy

Running your Keyence at a low frequency (stock setting) should keep it cooler then a high frequency (mod setting). Did you have the heat sink installed on the esc?

Running a 6 turn motor on a tight carpet track will be brutal on any esc. All top of the line esc's seem to really struggle with the abuse they receive from low turn motors. This has been my experience anyway. I cooked my Keyence zero V extreme using an 8 turn an 12.5kHz frquency.

Herminator

Lower frequency will create more heat actually, like Matt says. With a 6turn on stock settings you're asking for trouble. You should have the frequency near the top of it's range.
It does sound like thermal cut off is kicking in.

sedanaddict

I do have the heat sink installed. I have been running stock all day, practicing for a big race tomorrow. I bought the 6 turn cheap and thought i would see what it would do. (i was in a rush to slap it in, run it once and go back to stock)
I normally run a 8 turn d5 or a 9 double kriptonite on the carpet track and i haven't had any problems. but I also took the time to change the setting to a "mod friendly" setting.
on a side note, the power difference between a 6 turn and an 8 turn is scary. I think i will stick to the 8+ motors and use the 6 as a conversation piece.
thanks for everyone's input.
Mike Lindsay

Rowdy

Lower frequency will create more heat.

This is the opposite to what the Keyence manual states. This is a quote from the manual "As you increase frequency, driving is smoother but the amount of heat generated in the electric circuitry increases. When using high-powered motor, we recommend that you limit the frequency of the drive, brake to 15kHz".

I am certainly no expert, so could somone please give a definitive answer and clear this up for me.

Herminator

Hmm, I'm not sure on this either, I'm going by the Mtroniks Cirrus manual, but 12kHz seems awfully high. The Cirrus has a range of 1.5-5kHz. I looked at the keyence manual online and it seems to reccomend 4.5kHz for a 9T on a fast circuit so I'd imagine 5 or 6kHz for a 6T motor.

Hopefully an electronics guru will clarify everything for us

Rowdy

The Keyence esc has a frequency range between 0.1kHz and 20.0kHz

STLNLST

iTrader: (32)

The stock drive freq setting is 1.5and I normally run a 8 or 9 turn mod with a 4.1 drive freq. A 6 turn will have a ton of power to begin with and running the drive freq that low with that motor may be placing too much of a load on the speedo. I'd also check to see if the gearing was correct on the motor along with the timing set on it. The two times that one of the driver's out here has had a 6 turn in their car we only had the timing set a 5 degrees. Hopefully you didn't damage your speedo and it works for your big race. Good luck!

Rory

i'm no electronics expert, far from it, but the way i see it there are two ways of thinking about it
1: the lower frequency will give more punch therefore somehow making the esc work harder (not heaps of logic there i know but oh well)
2: the higher frequency will mean the FETs are switching more (or something like that (again im no electronics expert and i'm not sure that FETs do switch but it rings a bell in my head) and would get hotter due to switching more often and of course working harder

dpaton

I'll toss a little knowledge on this one.

Background:
FETs have 3 operating states: on, off and in between. That in-between state is called the linear region, and is what is used when FETs are designed into audio amplifiers. Most fets are practically lossless when they are all the way on. They ahve a very very low voltage drop, and dissipate a very small amount of current compared to transistors (0.01V or less vs 0.7V respectively). When designing a PWM system, the goal is to maximize power denstiy. You want to move the most charge from one place to another in the smallest box with the least loss posssible. If you need to vary the amount of charge transferred, you pulse the charge from full o to full off to full on, etc. The amount of time each pulse is either on or off will determine the effective DC voltage at the other end. The raw PWM signal isn't very good for driving motors however. It's rapid pulses generate heat and soem ugly magnetic losses when run though a coil of wire spinning in a magnet. That's why we have those big caps on out speedos. They are a special variety of capacitor, designed to run at very high frequencies and smooth out the PWM waveform so it looks like the DC our motors know and love.
Everybody with me? Good. Now on to the frequency stuff:

Lower frequency gives more 'punch' because it's closer to real DC, and thus is filtered much much better. The doen side of that is that it makes acceleration and braking a lot more chunky'. Remember the old Novak T-4? Compare it side by side to a GT7 and you'll notice how much smoother the new ESC is. It's a trade off. Personally, I like about 1500Hz on the gas and 7500hz on the brake, but that's me.

To finally get around to the question...

The higher frequency means the FETs switch more often, yes. When FETs are swiched properly, they do it nearly instantaneously, and go from off to on and back so fast that the time they spend in their linear region is pretty much nil. That's whyv the new generations of speed controls don't need heatsinks fo rmost things, unlike their predecessors. There is basically no power dissipated by a good fet if it's either all the way on or all the way off. If Keyance says higher frequencies generate more heat, I'd suspect it's one of the following possibilities:
1. Someone mis-translated the manual.
2. The FETs aren't being switched on and off fast enough
3. The FETs are very lossy, and dislike being switched.

My gut says it's #1. All else being equal, higher frequency switching is better for getting more amps through a small box without much heat.

-dave

John Fontaine

iTrader: (2)

I just bought a Keyence zero v-extreme 2002 for my Yok SD. I feel it's going to be a good esc for this car. If anyone could give me any tips, I would appreaciate it. This is my first keyence, my other two escs are a Novak GT-7 and a GM V8.

Thanks,
John

snoboardin

does anyone have problems with the buttons on the side being too sensitive when programming?

DickemDown

iTrader: (3)

i run my driver freq. @ 7.8 for stock and 8.4 for 19t - i haven't run any motors lower than 19t.

MattW

Personally i only change 2 settings from standard. Frequency - usually about 5KHz and neutral width - down to either 0 or 1. I think it is 9 as std and this is too wide.