Variable Frequency Drive and an Oh Crap! switch.

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Forum topic by Luthierman posted 10-01-2016 11:15 PM 394 views 0 times favorited 1 reply Add to Favorites Watch
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221 posts in 1236 days

10-01-2016 11:15 PM

I understand the way I need to wire this but I don’t quite understand how it works. The existing switch I have for my old unisaw is the standard high voltage switch that comes with it. What I am pondering is whether or not these types of switches require high voltage to function? If I remember correctly, the voltage coming out of the vfd to wire an external switch, which disables the on board on/off switch, is pretty low. I know that some switches, not all though, will require a full 240 to actually make the disconnection. I thought about wiring the switch in before the vfd instead of the way I am describing above, but I don’t think that will be very safe as the motor will not have any electric braking and will just wind down naturally. Not nearly as cool or safe as what the vfd will do. I could also wire in no switch, but the placement of the vfd is kinda inconvenient due to its requirements for little to no dust. It cant exactly be mounted directly to the saw. Anyway, perhaps someone can shed a little light on this for me.

Thanks in advance.

-- Jesse, West Lafayette, Indiana

1 reply so far

View 01ntrain's profile


257 posts in 1219 days

#1 posted 10-01-2016 11:34 PM

The VFD should have a low voltage bus that is designed to add in a remote on/off or in your case, a safety switch. It should be 24vac. There are some good examples on Google for just what you’re looking for.

If it were me, I would buy a 2-hole switch box and put in a momentary-on switch along with a big red E-stop switch. Hang it where the old on-off switch was.

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