Noob question - 9fet vs 12fet?

[Xanda2260]

Hey guys, long time lurker here. Firstly I'd like to apologise if the answer to my question is on here somewhere. I've searched for hours and failed to find the answer, so if someone could point me in the right direction?

What's the difference between a 9 fet controller and a 12fet? Obviously, 3 extra fets, but what does that do? Im specifically looking at the infinions and the lyen edition controllers.

Many thanks in advance

Alex

 

[dogman dan]

More fets, and better quality fets are able to handle larger current loads. So for big power, 12 fets is the starting point. 9 fets is plenty though, for a bike with lower amps that is expected to use lower power levels for longer range.

 

[neptronix]

More fets generally = more amp handling ability.

So for example, a 6fet is pretty much tapped out at around 25amps, and are ran as low as 14amps.
A 9fet runs as low as 20 or 25amp.. and i think they can handle 35amps or so.

Dunno much about 12fet, i know guys are running them in a 40 - 50amp range.

As you get more FETs, the controller gets bigger.. so get what is appropriate for your application.

 

[gwhy!]

or you can upgrade the fets.. i.e Im running a 6 fet at 75A continuous.

 

[CamLight]

Properly designed (and that's CRITICAL), a 12 FET controller can typically handle more current/power than a 9 FET model. But, it all depends on the effectiveness of the cooling, the FET drivers, the type of FET, how they're mounted, assembly quality control, etc. Designed well, a 9 FET controller can easily beat out a 12 FET controller that wasn't designed as well. In fact, a 9 FET controller can cost less as parts costs are lower and the possibly lower current/power handling can be addressed by careful cooling and component selection.

But, typically, a 12 FET unit can beat out similar 9 FET units.
IMHO though, it's best to check the specs and choose the model you want that way. Oh, and a good warranty helps too.

 

[grindz145]

I wouldn't bother with a 9 fet. Go 6, 12 or 18 (or 24 or 36 ). You really need a set of 6 fets to commutate these motors, I've never really understood the 3 extra. Even in theory the benefits are minuscule.

 

[spinningmagnets]

Since these motors are 3-phase, when you want to add more current to the motor you add one more FET per phase, so...6-FET, 9, 12, 18, etc

A FET is a "Metal–Oxide–Semiconductor Field-Effect Transistor", or MOSFET. Its an on/off switch that sends power to the coils in the stator to turn on and off the magnetic field at just the right moment.

The size and quality of each brand and model of FET can vary, plus the size and quality of the heat-sinking can affect how much current they can flow. A quality 9-FET might work better than a crap 12-FET. I am still learning, hope this helps...

 

[wrobinson0413]

.

 

[Xanda2260]

Guys, you are awesome! Many many thanks. Looks like I'll be trying for a 12 then!

Thanks again

Alex

 

[zombiess]

or you can upgrade the fets.. i.e Im running a 6 fet at 75A continuous.

What fets are you using?

 

[zEEz]

What fets are you using?

Looks like it must be something tough, probably
IRFB3077 if TO220 or maybe IRFB4110 ...
I WANT THEM TOOOO MANYYYY OF THEM

 

[wineboyrider]

From a laymans point of view a 9fet controller is a good commuter controller and a 12 fet controller is a racing controller. The overall quality of the controller does matter so do your research and ask more questions?

 

[The Mighty Volt]

As a general rule more FET's are better for extended periods of high-current handling.

However, the matter can be complicated when you get to considering the different types of motors and their windings.

As a general rule, avoid low-fet controllers when running a 5303 at high amps.

A controller that won't blow up when using a 5305 might blow up when using a 5303.

IceCube is the man to talk to about that particular issue- read his threads.