[Dbl_Tap]

I've been searching and was hoping someone had already answered this one specifically but did not find it.

I have a https://www.amazon.com/gp/product/B09Z8VBQSS?th=1 VFD and a water cooled ER20 3kw 220V 10A 400Hz Spindle and want to add a braking resistor.

Yesterday I cutting new fixture holes in my spoilboard I hit a bolt I thought I had accounted for. It stalled the spindle as it broke off the carbide bit. On my old undersized VFD this would error but a power cycle would fix it.

With this VFD it threw an Err01 and power cycling would clear the error but hitting start on the spindle caused it immediately. Disconnecting the spindle and programing the VFD so I could run it from the front panel causes it to click and Err01 instantly when I hit run so I am pretty sure this caused an IGBT failure so I guess I'm replacing this drive.

It looks like if I had had a braking resistor this could have saved the VFD but I am not mathematically gifted enough to figure out which one.

I am pretty sure I need at least a 22ohm resistor but after that I'm lost. Is bigger better on the watts? https://www.amazon.com/Xiaoyztan-Wir...1zcF9hdGY&th=1

[joeavaerage]

Hi,
I don't think a braking resistor would have saved you. The VFD did not s****t itself because it was decelerating, it was operating into a stalled spindle which causes a huge
spike in current demand. It would appear from your description that the VFD protection did not act quickly enough to save itself. Cheap VFD's tend to do that.

The correct size of a braking resistor is published by the manufacturer...no need to guess.

Craig

[Dbl_Tap]

Thanks Craig,

I guess I read misinformation on it then. I had read that from a sudden crash a brake could absorb that spike and protect the VFD from the spindle.

without breaking the bank what VFD would you recommend that could handle something bigger than a 3kw 220v spindle in case I ever upgrade?

[joeavaerage]

Hi,

I had read that from a sudden crash a brake could absorb that spike and protect the VFD from the spindle.

No, you have that correct, but that is when the VFD calls for a large deceleration, then yes the spindle will 'back generate' into the VFD, and the braking resistor is supposed to
absorb that current.

In your case the spindle has stalled by virtue of hitting the bolt and the VFD has carried on but has tried to supply many times its rated current....and failed.

I use Delta VFD's and servos. Delta is a Taiwanese brand made in China. Good quality, support, documentation, setup software at fair prices....but at quite a premium over the cheap
Chinese made stuff. I'm not saying you could not blow up a Delta VFD, but I've installed twenty or so over ten-fifteen years and nary a one has failed.

A VFD would ideally have what is called 'cycle by cycle current limit'. Many of the better VFDs have just exactly that and can therefore go into a safe current limit mode within microseconds.

Craig

https://www.fasttobuy.com/delta-inve...ol_p34121.html

https://www.fasttobuy.com/vfd037m23a...ne_p31636.html

https://www.fasttobuy.com/3-phase-vf...ne_p34130.html