Quick question: Let's a 30A rated ESC (3s-4s) will be limited by the power, or that particular current limit?

Thanks 

Current

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Quote from: Aravind298 on August 16, 2017, 06:44:27 PM
Quick question: Let's a 30A rated ESC (3s-4s) will be limited by the power, or that particular current limit?

Thanks 

Wording of question a bit odd.
Ans: Limited by current rating, as well as no. of cells rating. Avoid pulling over 75-80% of the amps rating

What I mean is, for a 30A rated ESC (3s-4s), can I get a discharge of 30A for both 3s and 4s configuration?
If so , would anyone mind to tell me how that works?

Lets say you are using an ESC i.e. rated for
1) 30A
2) can handle 2-3s

(All this information can be obtained from the product manual or website)

What does it say?

In theory this ESC can handle continuous current of 30A with 2S/3S battery.

So you can pull max 30A from this ESC without any problem but you can not use a 4S battery since the ESC is not rated for 4S (it will burn it)

But to be on safer side you pull max of 22.5A to 24A

You can get 30A of discharge for both 3S and 4S configuration. (obviously the ESC should be rated for 3s and 4s)

Regards

If I am correct, ESCs are basically limited by current (given Vds is well under its limits) (and hence also on its max power dissipation before excessive heat causes damage), given they are used a switch in MOSFET's saturation region. That doesn't mean you can apply higher voltages than what ESC is rated for because that might damage the internal electronics and mosfet drivers.

It is limited by the Id (Drain current) of the mosfets used. In saturation region of MOSFETs Id is also "almost" constant. Change in Vds (Drain to Source) (which is applied to motor) has "almost" no effect on Id. 

When you are using the mosfets near its limits, it will dissipate more heat, which in turn will increase Rds (Drain to Source Resistance) which in turn will add to more heat dissipation given by: P(Rds) = Id*Id*Rds.

So, for a 30A ESC(3s-4s), you can get a discharge of 30A for both 3s and 4s but then, you would be operating at the ESCs limit and will it will generate excessive amounts of heat due to power dissipation in the mosfets. Thats why its not recommended to operate ESCs at its maximum current for significantly long amount of time. You will be good operating at upto 85 to 90% of the rated amps. As KK Iyer mentioned to be safe, don't use it above 80% of the rated amps.

-Regards.