disconnect location

I have come accross this problem before.
The solution that I have used up to now (which was copied from someone else) was to use an isolator with an early break auxillary feeding back to the VFD.
When you turn off the switch, the auxillary breaks first, causing the VFD to lose power. Normally by the time the main contacts break, any danger to the isolator or VFD is eliminated.
I have also found by experience that for some VFDs this won't work.
Example, Movidyne VFDs from SEW driving servo drives.
With these ones, we had to run the cable feeding the VFD out to the field, through the isolator, then back to the VFD, then back to the motor.

Depending on what type of VFD you have depends on the solution you use.

...wow , this makes great reading while watchin Letterman after I get off the afternoon shift at night. I will continue to call it a motor terminal box....except at parties if I talk shop !! thx

.....they are TBWoods WFC5000 VFD's .....and some are AB drives in different app's ....


...I gather from all this another prob is the VFD could be damaged or " fried " if this disconnect between the motor and the drive is for some reason switched off when the motor is runnin....another prob I did not think of.

Like I said , these disconnects have been " added in " as an extra after the initial engineering and machines have been runnning for years.

I have an easy way to show whomever "added them in" why they might be a bad idea...

Bring them out to the machine and have them watch you flip the disconnect switch randomly off and on a few times while the machine's running. If the disconnect was implemented correctly, this person should not "cringe" when you do that... utoh

If the machine makes terrible noises and/or starts smelling funny, instruct that person to replace the (now dead) drive and re-think their installation...

beerchug

-Eric

Sounds like who ever had the disconnect switches installed, as an after thought, had their thoughts in the right direction, towards safety, but just didn't know how to accomplish it.
Hopefully you can talk to this person and correct the situation before any drives are damaged or worse yet personnel.
(Damaged personnel is bad)
Do place the disconnect switches ahead of the drives.

Roger