Hi,

When we talk of 40A or 60A rating of ESC does that mean the the max limit the device can allow or what? What happens if an equipment/motor tries to draw more?

Pankaj

ESC selection is normally around 1.5 - 2 times the motors max current draw .
Hence technically the ESC should not be affected by the Motor drawing its max amp.
Normally when I  evolve a system for my set ups what I do  as a rule of thumb is as below :

1) ESC  Rating  1.5 - 2 times Motors max amp. which means if the motors max amp is 16 amps , I selects a 30 amp ESC.
2) Battery Max Discharge capablity 1.5  times the ESC rating  eg for the above I will select a 3 S that can deliver around 45 -50 amp  eg  a 25 C 1800 mah or a 20 C 2200 mah.

The advantages I have experienced in this case is the costliest  component the battery is not stressed at any time . So in the event of the motor drawing in excess of the Max amp both the ESC and the Battery will not get damaged  and at best the Motor might burn out and  since the ESC is safe the model will continue to receive commands and the receiver will not be shut out  and you could still glide it down to a relatively safe landing  thus minimizing damage to the model . 
The important part is also to understand the BEC's  capability of the ESC , normally beyond 40 amps external BEC has to be used  .

Sai

Quote from: rcforall on August 13, 2009, 12:20:52 PM
costliest  component the battery

well they aren't that costly either in my case actually lesser than my rx and motor and esc itself

http://www.hobbycity.com/hobbycity/store/uh_listCategoriesAndProducts.asp?catname=Rhino+Lipoly&idCategory=252&ParentCat=85
http://www.hobbycity.com/hobbycity/store/uh_listCategoriesAndProducts.asp?catname=Turnigy+Lipoly&idCategory=317&ParentCat=85



subbu

Subu ,
You see when you get a battery or two by post and don't get charged  customs  is more an exception than a rule .

Further the batteries you are showing here are small capacity 2 S mostly .

When you get to higher capacity and higher discharge levels then is when battery cost  are significant .
Look at a 3 S 4200 or 4300 or 5000 mah with 25 C discharge .Also look at 25C batteries around 2200 mah and you will see their prices are far far higher than those of the motor and ESC put together .

Subu please don't make me say it again and again your experience and time in the hobby has its limitations .

sai

Sai,
If the current being drawn is in the tune of 30 - 40 amp or more. Won't the components get really hot? Is cooling required? are these levels good for fomie?

Pankaj

Pankaj ,
Cooling is essential mainly for the ESC  but my experience has shown that over all cooling is good for the entire system.
In fact in some of my planes I keep the ESC outside the fuselage.
Further if you keep the equation of the ESC to motor to battery as mentioned earlier the system does not heat up.

You will have heating problems if all the components are working at their maximum levels eg motor draw 40 amp , ESC 40 amp,Battery 11.1V 25 c 1800 mah , if you see each is capable of 40 amp max in this example  so for sure the system will be heated.

Sai

ESC cooling...  sounds vaguely familiar....

http://rcqatar.com/helicopters/scorpion-commander-45a-esc-heat-problem-solved/

i guess the 30-40 amp levels you are saying is not suitable for foamies.