# The "Big Red" Button...How to wire and install one with a VFD



## HMF (Dec 14, 2011)

I plan to hook up my lathe and milling machines using a disconnect (knife) switch in a box after a plug into the 220V phase 1 wall socket, then to a VFD usign remote controls.

I was told that on the on-off-reverse remote controls on the machine, I should have a big red "emergency off" button.

Can anyone explain how this gets hooked up? I presume it doesn't get wired to the VDF, because you want the power off before then?

Diagram would be helpful.

Thanks,


Nelson


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## Tony Wells (Dec 14, 2011)

Usually the panic button should apply brake to the motor, so it's more than a simple power kill switch. I don't run a VFD in my shop at all, yet anyway, so perhaps someone who has approached this problem will chime in.


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## British Steel (Dec 14, 2011)

What I've done is in 2 stages - the "Emergency Stop" buttons cut the 24v DC from the VFD control side to the Fwd/Rev switch, so the machine stops fast with DC braking - much safer (I think) than coasting to a stop with the power off (which most VFDs do, I suspect). THere's also an "Emergency Power Off" switch which drops the main AC inout to the lathe - just the lamp and the motor cooling fan are left running.

It *might* be possibe to combine these, as some VFDs will do regenerative braking - that way a single multipole contactor (e.g. a 4-pole one meant for 3-phase) could cut the AC input and the control voltage together, the regenerative braking would maintain the VFD's DC bus voltage for the duration of the stop?

I've attached the wiring diagram for my lathe, but it may be more confusing than enlightening - it's a bit complex. Overkill, even.

Dave H.


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## Kennyd (Dec 14, 2011)

I don't have a "E-Stop" on my lathe, I just rewired the original controls (drum switch) to now control the VFD.  I also added a external resistor so I can stop it really fast.  Some VFD's also provide for a E-Stop switch.


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## bedwards (Dec 14, 2011)

The Teco unit I have has an estop that kills the voltage to the relays that power the 3phase motor. The motor will then coast to a stop. Any style of Stop is wired as normally closed. (Push the button, open the circuit, and the "relay" drops out). This is the option I used. 
It also has an option to feed the motor into a bank of resistors (optional) to kill the motor rotation instantly. This last option can make magic smoke appear if not wired right or the wrong sized resistors used so I chose not to use it. 
Here is a copy of the pdf I used to help me understand the wiring on mine but I bet yours is different. 
hope it helps

be


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