Fuse rating question

[paulwes83]

Hi everyone,

I'm going to be installing a Gate Pico SSR3 mosfet into my AK and it states that the "advanced" set up requires a fuse. I'm familiar with the types of fuses in most airsoft guns, 10A, 15A, 30A and 40A, but is there a need for a larger fuse in a non PTW build? The Gate manual shows the smaller 10-15 cylindrical fuse, but I noticed that my DBoys V3 gearbox has one of those flat fuses...not sure of the rating on it though but all the ones I've seen online of the same shape are rated at 30-40A.

I have upgraded 16awg wiring and am going to be running an 11.1V 1500mah lipo into an SHS high torque motor with deans connectors and gold plated motor contacts. I know this might not be a terrific set up, but I don't want to spend anymore money.

Thanks for your time and please let me know

[pestobanana]

Gate recommends a fuse because their MOSFETs are horrible.

Pick a fuse based on the rating of the FET. If its only designed to handle 30A you need a fuse that will blow before your current reaches that amount. I've had Gate FETs rated for 30A blow in 20A setups though. Obviously a "quality" product.

[EOD Steve]

Gate FETs go not due to current but inductance causing voltage spikes. MOSFETS are sensitive to that kind of stuff. Exceed it's absolute max Vds by 1% and it's dead. Brushed motors are super inductive.

To answer OP's original question, the architecture of the fuse does not matter (cylinder, flat, round, whatever), only the rating matters.

[paulwes83]

Thanks guys that fully answers my question. So in short, the size of the fuse depends on the limit of the mosfet and is just to protect it should a surge happen. Thus, a fuse should be rated lower than the mosfet so it blows instead of the mosfet.

Feel like a bit of an idiot now since the whole point of a fuse is to protect whatever it's in front of. haha

[Azathoth]

Be wary of going too low a Amp rating for a fuse, It's nice to protect your boards etc, but false positive blow outs are annoying.