New GFI 110v outlets blow out TECO VFD

[ch2co]

I started out with a 4 wire twist lock plug but changed it out to hard wiring from box to the VFD. Licensed electrician friend approved it all and said the wiring I did was pleasantly overkill for the application. All 110v outlets are GFI protected and have caused no problems with any other shop tools.

 

[jim18655]

I think there was less discussion at NASA for the first moon landing

 

[Blackjackjacques]

Jacque: there is a slight interwinding capacitance however which might produce enough current to deliver a mild shock.
Mark

At high impedance, there may be a measurable voltage owed to capacitance, but it should go to flat at low impedance. ISO transformers are often used to decouple metal hulls and protect against stray current corrosion owed to shore power as well as in patient systems involving electric current as a means of protecting against a ground fault, etc. so any current at practical loads (low resistance) will be zero. Sure, if you connect a high z meter across a secondary leg and ground, you may read voltage, but the current will be micro amps, and as soon as you place a load across, the voltage will drop to zero.

 

[Blackjackjacques]

I seriously doubt that. If electrical potential is present, it will drain to ground. And if anyone wants to test this, please use a meter or tester, not your hands.

Of course and I would also not test with my hands--I used the "hand" model because the hand surface area against a flat metal surface is what is used by the testing institutions and the electric shock safety standards (IEC 60479-1 in particular) as the basis for such safety. However, if you have an ISO transformer and measure current from a secondary leg to ground - it will read zero or close to it.

 

[4GSR]

Okay guys, we all have spoke with our ideas of what to do.

The OP has to follow what the local building inspector say he has to do. Our say so's don't count.
So let's move on and put this to rest.

Ken

 

[coherent]

May be a silly question but I didn't see if you said or what your motor HP rating is but... Are you running a 15amp or a 20amp breaker/receptacle? Most 110/120v to 3ph VFDs that I have seen call for a 20 amp circuit/receptacle for a 1hp motor. I'm sure a 1hp is pulling close to or more than 15 amps on startup and GFI breakers always seem a little more finicky. So if it's a 15 amp setup that could be the issue.

 

[Blackjackjacques]

My curiosity got the best of me and so I had to update myself on GFCI's and found this excellent IAE article indicating new GFCI classes for industrial applications and higher voltages still providing human shock protection. The article is well done and is good reading.

https://iaeimagazine.org/magazine/2...have-a-proactive-option-for-shock-protection/

 

[markba633csi]

I had a great old electronics teacher, Mr. Evans, used to stick a paper clip in the outlet and invite us to feel the electricity.
He said "don't worry you have at least 1 million ohms from your finger to your toes. He didn't have many takers. Not even me, and I've had many shocks
Just a wimp I guess LOL

 

[Latinrascalrg1]

Ok you (OP) stated that you added 3 GFCI outlets, were those 3 outlets each individual home runs back to the breaker box or are they on the same line as a single home run back to the breaker box? Or did you tap into an existing circuit? If they are on a single line either back to the box or tapped into an existing circuit how did you wire them? I think I remember either being told or reading the following information so I'm not sure of the validity of this so please read it more as a question to verify verses me stating a fact.......I think i remember that running more then 1 GFCI on a circuit will make them fault out and act crazy. You should only need 1 GFCI outlet that can protect all outlets past the gfci on the same line if you wire it so that you utilize the Line/Load terminals of the gfci correctly! (I would assume this would be dependant on the local codes and what you will be powering?)

If this is not correct info would you explain what is not correct for me so that I know for future reference please? Thanks.

 

[whitmore]

I agree that the iso transformer would render a downstream GFCI inoperable since there would be no ground reference...

Happily, that's not the case. GFCI is the recommended way to make-shock-safe a
two-wire (neutral and line) receptacle even when there is no ground wire available. There's little
labels supplied with the GFCI so you can tag those outlets as not-grounding.
So, a short extension cord, with a GFCI on the end, is a worthwhile precaution
if you have two-wire or ungrounded (or just uncertain) power outlets.

With an ISO xfmr, you should be able to grab any secondary lead in one hand, and place your hand flat on a solid ground surface and experience no current.

Not always !!
Isolation transformers are available in TWO different types, either with neutral/ground bonding
on the output side, or with neutral floating on the output side. If you want shock-safe
due to transformer isolation while working on live circuits, only the neutral-floating
type is going to work for you. This item TrippLite iso transformer has a 'N-G' output
limit of 0.5V, indicating that it has the neutral on the output bonded to ground on output (from
the third prong of the input wire). Hold the output LINE wire, touch a ground, and you get a shock.

It's confusing, and a little scary, that the 'isolation' situation is so poorly described. I've
tested both types of isolation transformers, they both DO have legitimate uses. A
three-prong outlet tester will 'fail' the isolation transformer output socket unless there's
a neutral-ground bond.