Brake Resistor for 1.5kw Spindle

My VFD has a hookup for an optional brake resistor to quickly slow the spindle down.
I can see this potentially being a nice safety feature in the case of an emergency stop but is there any other benefit to using one with the Shapeoko? Does anyone have a brake resistor installed on their VFD?

Even without a brake resistor you can stop a the spindle within a second which will be faster than you can press the E stop.

I need to revisit my acceleration settings, because my 1.5KW spindle takes ~8 seconds to spin up and down from 20k RPM.

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brake resistors are great if you’ve actually hit the limit on settings and want to shave more seconds off decel. most of the time, and particularly with these smaller spindles, you can tweak the settings further - sometimes it’s multiple parameters that need to be set correctly.

usually where a braking resistor really shines is on spindles with a lot of rotational mass. i have a belt driven lathe with a 6” chuck and the resistor made a significant difference to dump that excess heat whereas the internal brake of the vfd was limited


Yes, should be able to tune your acceleration and deceleration settings. You just need to monitor the VFD while tuning to sure it doesn’t overload during the startup and shutdown ops when not using a resistor (or if an ext resistor is used but not rated high enough). I.e. deceleration usually goes back on the DC bus and can over volt it, causing the VFD to shutdown or worse damage it if the safety features don’t act quick enough.


Thanks for that. I’ll definitely be playing with those settings when I get off work today.

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Thanks guys. That’s valuable information.

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