Current limit parameters

[Bigpie]

Does anyone have more info on the current limit parameters and a procedures for setting sensible values?

ocurlim, for example, I've read in a post this is motor current and that it might be much higher than the battery current at low RPM. Is there a rule of thumb to set this high enough for decent performance?

Then there's the values under de-rating, iacmax is this motor amps? Should it be lower than ocurlim?

idcmax, should this be the same value as the fuse or higher? The datasheet for the fuse says it can do 3x it's rating for 19 seconds.

What happens when a de-rating limit is reached?

I'm using FOC on a prius gen3, but want to understand the parameters more, so any info would be appreciated and I'll use it to update the wiki.

[celeron55]

You should set ocurlim to something less than what will break the inverter. Openinverter handles it kind of like a fuse, erroring out if it's reached, and it's handled more in hardware than software so it's able to stop misbehaving software, at least sometimes.

iacmax is peak motor amps and should be set to something the inverter can handle, unless you have a silly small motor that has to be limited lower than what the inverter can do. It doesn't act like a fuse so it obviously should be lower than ocurlim to avoid overcurrent events. iacmax is basically a torque limit also, so you can set it lower if you need to limit torque for some reason.

You can go a bit higher than your fuse rating for idcmax especially if you have a small battery that will limit the discharge duration. Maybe 10% to 40% depending on battery size. Of course it doesn't make sense to do this unless you need to. idcmax is basically a power limit also, so you can set it lower if you need to limit power for some reason.

When a de-rating limit is reached, openinverter will try its best to stay below the limit by reducing throttle input.

[Bigpie]

Thanks. Is there a way of working out a sensible value for each that's not too low to inhibit performance or is it just trial and error?
Is there a relationship between motor current and battery current?

Just seen viewtopic.php?p=11806#p11806, so I guess ocurlim of 500 would be a good start

[Bigpie]

Gen 3 prius inverter, ocurlim set to 900 but this is stopping with OVERCURRENT, any hints as to why?

[ZooKeeper]

I checked the Parameter database and one user has the idc set at +/- 5000A and ocurlin = 300A as well as throtcur = 1.0A/% (as do I) with success.

[Bigpie]

I'll do some more faffing tomorrow. It's nice and lively with higher throtcur, but only goes for 1 second before bumping off. Setting of 3.6 I can put foot to floor, 3.7 cute out, but my de rating parameters are lower than overcurrent, that's what I'm failing to understand, why it's not derat8ng instead?

[Jack Bauer]

So what you need to understand is the desat circuit in the inverter is analog. The STM32 is obviously digital. An analog circuit is thousands of times faster. So by the time the mini Johannes brain sees the current limit the Toyota engineers have shut you down, gone home, had a cup of tea and are catching up on the latest episodes of world's fastest electric car.

[Bigpie]

Gotcha, Toyota says no. So he'll let me have 360amps with a smile and a wave but 370 is a big no without bringing in mg1 too.

Hopefully not going to quickly find out the front outlander motor is too weak for the job.

[Bigpie]

It's been quite usable so far, just have to make use of first and second gears. I hit what I'm assuming to be field weakening at 60 in second. Hoping with further tweaks I can just use second from standstill but we'll see