Topic: Odlican tekst koji objasnjava zasto se ESC vise grije na pola gasa ( ponekad ) (Read 2648 times) previous topic - next topic

Ja nisam vjerovao dok to nisam dozivio da je ESC vrel od lagane voznje a na kucnom testiranju pod punim opterecenjem hladan.

http://www.rcgroups.com/forums/showpost.php?p=23079870&postcount=5

At full throttle, some of the better ESC's are as much as 98 to 99% efficient. At lower throttle settings this can drop to 95% or so. This may sound like extreme efficiencies, but whe you look at how much power is actually going through the ESC, that 1 to 2% of inefficiency adds up!

For example, if you have a 6-cell ESC that is running at 100 amps at full throttle, you have 22.2 volts x 100 amps of 2220 watts of power going through the ESC. At 98% efficiency, you have 2% of energy lost to heat. 2% of 2220 watts is 44.4 watts of heat energy, which is significant. If you figure that the average soldering iron puts out 40 watts of heat, you get teh picture on how much heat that actually is!

FET transistors are marvelous little devices that essentially act like a switch. When they are turned off, the resistance is virtually infinate, when turned on, the resistance is extremely low, often just a few thousandths of an Ohm. So when the FET is completely on or completely off, there is very little power dissipated in the FET's. The only thime they really generate significant heat is in the process of turning on and turning off. During this transition, the FET's are operating in the linear range of operation, and it takes a small but finite amount of time to turn on or off. During this brief time period, the transistors generate most of their heat.

When a Speed Controller is running at 100% throttle, each set of FET's only turns on and off once per phase cycle. You can see this in the photo below that shows the voltage output of one phase of a brushless ESC with the throtle at 100%.





Whenever you run at less than 100% throttle, the PWM effecet of the ESC kicks in, and the FET transistors start to switch on and off multiple times during each phase cycle of the ESC. This usually takes place at 8000 times per second, or 8KHz, which is the PWM switching frequency of most ESC's. The photo below shows a speed controller running at 60% throttle, in this example, you can see how the FET's are turning on and off 4-5 times per phase cycle.





This extra switching places the FET's in the linear region for a longer period of time, which causes more heat energy to be generated. If you have 5 switching cycles per phase pulse, as seen above, you have 5 times as much time that the FET's are in the linear mode. If you are running at 60% power, then your average current would drop from 100 amps to 60 amps, so most people would think tha the ESC would run cooler. Unfortunately, this is not the case! Even though you are only pulling 60% of the original current, the FET's are subjected to the current 5 times more often, so in the end, the ESC has to dissipate almost 3 times as much heat energy running at the lower throttle setting than it did at full throtle. This is why it is foolish to think that it is OK to run an ESC at lower throttle settings to account for an ESC that is actually too small for the job.

The best thing you can do is ALWAYS, ALWAYS, ALWAYS use the 80% rule when sizing components. Never use an ESC, Motor or Battery at more than 80% of it's rated value. If you need to pull 80 amps, use a 100 amp ESC, if your motor is capable of handling 50 amps of current, never pull more than 40 through it and so on. If you abide by these simple rules, you will virtually never have problems with your electrical components.

Lucien

stvarno zanimljivo i opisuje siutaciju koju sam imao na easy staru II

znači stock prop 7x6 i spinner

esc, je ljubičasti HK 40A

od mpx-a predviđeni motor za taj prop i spiner je 1100 kv

prvi motor je bio rc timer 2200kv

iako taj motor uredno radi sa 7x6 elisom kod plavog na zagiju, a on ga baš ne štedi kad sam ga ja montirao i vozio sam ga na 1/2-3/4 gasa, iz opreza da se krakovi ne "razdvoje previše" regler se grijao do točke da se nije mogao držati prst na njemu

kad sam stavio kda 1200 kv motor, ni  nakon par minuta na full gasu, regler je mlak, a struja je otprilike jednaka na njegovom full-gasu koliko je bila na pola kod ovog...

ili je jednostavno ovaj regelr bio djubre...

Da, zato se na helijima mijenjaju pinioni, uvijek je bolje "više gasa".
Neki ESCi mogu žvakat manje postotke gasa (posebno Kontronik recimo). YGE dobro radi do 50%, ispod toga ne baš. Ne znam kak se Castle s tim nosi, ali budući da oni vole gorit kak god ih voziš, nisam isprobavao (niti neću )

pisao sam o tome pred godinu i pol skoro, popraćeno grafikonom da ne bude samo rekla-kazala
a i poslije po multirotor sekciji,
http://www.flyfreak.net/elektro-modeli/het-me-163-komet-prop-jet/msg43989/#msg43989

kada leti kombinirano, nekad i s pola gasa, temp je 59°C u peaku,
a u letu di je samo full gas ili ništa je 48°C najveća vrijednost. 


osobno provjereno na više modela,
regler je hladan ako radi na 100% a sve je dobro instalirano
(da regler ima više A nego što motor cucla, i da batka to može sve nahraniti)
a ako isti taj model leti na pola gasa, i troši puno manje A iz istog tog reglera, može se i pregrijati do cut-off limita.

isto tako bi bilo dobro spomenuti i da preduge žice do reglera dokazano ubijaju isti,
ja sam to prvo primjetio kada me opekao ESC dok sam mjerio potrošnju wattmetrom,
wattmetar mi doda nekih 40cm žice u sustav, jer ima konektore i ubaci se u seriju između batke i reglera,
nema pada napona, debela je žica i za 200A, ali induktivitet čini svoje na regleru,
tko ima doma može probati, najbolje na pola gasa, opisano gore zašto,
pa nek drži prst na regleru 2 min bez dodavanja i onda s dodanom žicom.

(poznato već dulje kod EDF modela, di su batke zbog CG-a sprijeda, a impeler u repu, pa di staviti regler)
http://www.rcgroups.com/forums/showthread.php?t=952523
baš zbog tog pwm efekta rada, dolazi do povećavanja napona na ulazu u regler,
pa iako je batka npr 16V, na ulazu u ESC napon može biti i 40V i više, pa to ubije i kondić i ostalo redom...
najbolje ostaviti kako je, oko 10-15cm, ili ako se ne može, da se dodaju kondići koji pomažu smiriti te oscilacije.

[attachimg=1][attachimg=2]

također bitno za multije, jer neki stave regler kod motora, a onda žice do batke pola metra,
ako se produže ove do motora, ništra strašno, ionako je u motoru namotano desetak metara pa nije neka razlika.

I will repeat the message previously given. I hope you heed some sound advice
based on theory and practice.
1. wire resistance my rob you of a bit of power but will not destroy
your speed control or motor.
2. wire inductance will not damage your motor nor will you be able to
detect any effect even with 100 feet of wire.
3. wire inductance will kill the mosfets in your control and may even blow the caps
I am a design engineer and manufacturer of motors and controls for over 30 years.
you must keep battery wires as short as practical . short means 1 foot or less.
brushed or brushless makes no difference.

here are some example of problems some customer have had
1. blimp 30 feet of wire to speed control and steering motor in the tail.
control voltage rating 60 volts 50amps motor load 12v 20 amps
result instant smoke first run of motor. I replaced control at no
cost . same result instant smoke. then i was told about long wires
ran a test with 3 ft cord result 30 volt swithching spikes on 100 uf input cap.
had customer put control near battery in gondola. 30 ft wire to motor
end of problems.

we have customers running very long wires to motors for industrial applications
with no problems. hundreds of feet or more.

on robots running two or more motors on one battery. 2 feet battery wires
to non opto coupled controls will make motors hunt. no problem with
opto coupled controls. with BEC controls keep battery wires short. PERIOD
astrobob

pisao sam o tome pred godinu i pol skoro, popraćeno grafikonom da ne bude samo rekla-kazala
a i poslije po multirotor sekciji,
http://www.flyfreak.net/elektro-modeli/het-me-163-komet-prop-jet/msg43989/#msg43989

kada leti kombinirano, nekad i s pola gasa, temp je 59°C u peaku,
a u letu di je samo full gas ili ništa je 48°C najveća vrijednost. 


osobno provjereno na više modela,
regler je hladan ako radi na 100% a sve je dobro instalirano
(da regler ima više A nego što motor cucla, i da batka to može sve nahraniti)
a ako isti taj model leti na pola gasa, i troši puno manje A iz istog tog reglera, može se i pregrijati do cut-off limita.

isto tako bi bilo dobro spomenuti i da preduge žice do reglera dokazano ubijaju isti,
http://www.rcgroups.com/forums/showthread.php?t=952523
baš zbog tog pwm efekta rada, dolazi do povećavanja napona na ulazu u regler,
pa iako je batka npr 16V, na ulazu u ESC napon može biti i 40V i više, pa to ubije i kondić i ostalo redom...
najbolje ostaviti kako je, oko 10-15cm,

također bitno za multije, jer neki stave regler kod motora, a onda žice do batke pola metra,
ako se produže ove do motora, ništra strašno, ionako je u motoru namotano desetak metara pa nije neka razlika.

Nisam mogao naci, pojasnjavao si to vise puta, tvoj ME163 je i dalje legenda.
Stariji thredovi se lako gube bez novijih postova.

yup,
kada se govori o ESC/A/iskoristivosti...
[attach=1]
mislim da je malo tko pojurio preko 200 tu kod nas pri svega 16C loada iz batke. Zato te batke i dan danas koristim,
(slope soaringom se nitko ne bavi, benzinci se presporo vrte pa ni oni ne konkuriraju) dakle samo elektraši su u igri,
a oni koliko vidim mahom briju na bijesne ampere
i te batke slete kipuće dole, bila su neka mjerenja IR senzorima u par navrata tu na forumu,
no zna se da ne mogu tako trajati dugo. 
A ovak kada je sve složeno kak spada u modelu, traje i traje...

pri evo kada se već spominje i ME163, 
listam temu o X8 na rcgroupsima, http://www.rcgroups.com/forums/showthread.php?t=1555543&page=400#post23086433
i neki dolaze na ideje da ga raketiraju u vis i brzo dobiju na visini, poput ME163 u biti...
ali evo kako to završi na testiranju    

JATO launch
http://en.wikipedia.org/wiki/JATO

JATO Predator Crash.mp4

(slope soaringom se nitko ne bavi,

Dlaka, K. Siniša, Marijan1,IgorUAV, Belovic, moja malenkost i još neki modelari povremeno.
Čak smo u jednom momentu razmišljali i o tekmi..

Slope saoaring nije što i dynamic soaring, no tu 300 nije rijetkost. Sa joticom bez problema ide 200 u startu.

Inače, ova tvrdnja da se jače grije na pola gasa je točna, ali je tumačenje razloga kao da ga je pisao neki chinglish-majstor  .

Damir

D.

lapsus, my bad 
zna se na što sam mislio, jedriličara ima puno i u Hr i to u 99.99%,
iako sve ima svoje čari i trikove i tajne, to koliko znam nema veze s brzinama preko 300km/h,

ima i indoor slope soaring
walkalong glider pylon racing

dakle kada govorimo o brzini, na dinamic soaring sam mislio,
njime se nitko ne bavi na ovim prostorima . a tu se postižu stvarno velikebrojke a bez motora i reglera   
jasno u prilično organičenim uvjetima i putanji letenja.

Spencer's World Record 468mph Kinetic100DP flight video!!!