Hello Guest it is May 20, 2019, 07:47:19 AM

Author Topic: Limit switch error when connecting VFD shielding to ground???  (Read 2609 times)

0 Members and 1 Guest are viewing this topic.

Re: Limit switch error when connecting VFD shielding to ground???
« Reply #10 on: April 28, 2016, 05:02:08 PM »
Great thanks! what should I do with the neutral wire from the 220v wall outlet? Do I leave it on the ground lug on the VFD as shown in the photo or should I move it to the 'T' terminal?
Re: Limit switch error when connecting VFD shielding to ground???
« Reply #11 on: April 28, 2016, 09:44:24 PM »
A 220V VFD doesn't need a neutral. Just tape it up. The "T" input is for 3 phase power input. If you connect the neutral to the "T" input it was destroy the drive and trip the 220V circuit breaker. Run a separate "ground" conductor from a water pipe or circuit breaker panel ground bar for the VFD "Ground" lug and motor cable shield. 
Re: Limit switch error when connecting VFD shielding to ground???
« Reply #12 on: April 28, 2016, 10:30:14 PM »
Okay guys I've heard enough hooey.  The VFD shield is acting as an antennae because of the RF noise that VFDs generate. Forget earth grounds  and stuff because if it seems to fix the problem you can be sure of one thing, you didn't actually find the problem or fix it. It will come back. Two issues here. Safety grounding which is intended to keep all grounded conductors from ever having an unsafe voltage difference even when 5,000 amps are flowing in a dead short. Safety grounding is all about creating as many ground loops as you possibly can. You can never know where the current will actaully flow so the idea of a clean ground is a myth.  Control NOISE grounding is a completely different animal.  The goal here is to never create a ground loop and only have one path straight to one ground for every device. No daisy chaining allowed.  Manufacturers, and PCs in particular make it tough because they hide additional grounds in places you'd never expect like on ports, sensors etc. A simple shielded cable plugged in a PC often creates a ground loop because there is a ground pin on the connectors at both. Plug into the PC powered from the wall outlet and connect to a device powered from the wall outlet and you have a ground loop. So for everything you connect you need to use an ohm meter to determine if it is already connected to ground before you connect any more grounds.
Re: Limit switch error when connecting VFD shielding to ground???
« Reply #13 on: April 29, 2016, 07:46:49 AM »
Thank you for your reply... too bad you are wrong. Anyone that says "Clean grounding is a myth" and "Safety grounding is all about creating as many ground loops as you possibly can." shouldn't be giving electrical advice. Seems you have no background with industrial VFD's and PLC's or any knowledge of machine grounding. If I can quote you.... I've heard enough hooey.

Offline Davek0974

*
  •  2,493 2,493
    • View Profile
    • DD Metal Products Ltd
Re: Limit switch error when connecting VFD shielding to ground???
« Reply #14 on: April 29, 2016, 07:58:37 AM »
So i gather what you have over there is what we would call "two-phase" ??

So live to neutral=110v and live to live is 220v?

We only really use single-phase (live to neutral 220v) or three-phase (live to live 415v or live to neutral is 220v) over here.

But you have a supply CPC (circuit protective conductor) or supply ground as well? Surely this is what must go to the VFD ground tab?

And I also disagree with the 'many ground loops" suggestion, AFIK a ground loop is bad in any circumstance and can do weird stuff as well as set up eddy currents and other oddities ;)
« Last Edit: April 29, 2016, 08:00:12 AM by Davek0974 »
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives