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VFD Manual info question about switch

John S01

Aluminum
Joined
Mar 5, 2017
Location
Sunnyvale CA
I am installing a new VFD drive for my 3 phase Bridgeport Mill on 110VAC in the garage. The instructions say not to install contactors between the drive and the motor. Isn't the drum switch on the mill between the VFD drive and the motor?

So I can't use the drum switch ever?

Here are the instructions

– It is not recommended to install contactors or disconnect switches between the drive and motor. Operating such devices while the drive is running can potentially cause damage to the drive’s power components. If such a device is required, it should only be operated when the drive is in a STOP state. If there is potential for the device to be opened while the drive is running, the drive must be programmed for COAST to stop (see Parameter 4 – STOP METHOD), and an auxiliary contact on the device must be interlocked with the drive’s run circuit. This will give the drive a stop command at the same time the device opens, and will not allow the drive to start again until the device is closed.

Thanks,

John
 
Last edited by a moderator:
If you want to use it, simply rewire the drum switch for Low voltage use and feed it to the start/stop/reverse inputs on the VFD, and program the VFD accordingly. I prefer separate start stop and reverse controls, but that wasn't your question.

You really need to read the rest of the manual and understand how VFD's are used in your context. Sounds like all you are trying to use it just as a phase converter, and although it can do that, you still need to control and program it it appropriately.
 
Thank you. So the answer is yes, unless I rewire the drum to work with the VFD. My drum switch turns out to control FWD & Reverse (even thought it is listed as Hi and Low (1969 Variable Speed), so I think I'll use that switch when off (if ever needed), and add a switch through the VFD controls inputs.
 
If the manual says not to do something, don't do it.

Some units are less fussy, and may allow a switch, but not ones that specifically say not to use it.
 
Just to make sure you understand, you no longer NEED the drum switch to make your motor change direction, the VFD can do that for you now. So the suggestion to repurpose that drum switch as the low voltage COMMAND signals to the VFD allows you to continue using it the way you are used to, while observing the safety concerns of the VFD mfr.
 








 
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