High Frequency GFI's…….. Some good information for you contractors.

[u3b3rg33k]

aww ok you didnt specify

regardless are you purposely touching an ungrounded phase and the grounded phase? i dont get it

here's what's to get:
I WANT TO KNOW IF THE 30mA RCD WILL ALLOW A VFD TO OPERATE.
i WANT to be able to run my VFDs on GFCIs.
that's it.

i'm not grabbing live phase conductors with my bare hands.
i'm not advocating doing unsafe things.

any other questions?

 

[wyliesdiesels]

here's what's to get:
I WANT TO KNOW IF THE 30mA RCD WILL ALLOW A VFD TO OPERATE.
i WANT to be able to run my VFDs on GFCIs.
that's it.

i doubt many people here would know this since 30ma equipment GFCIs are not in widespread use. I rarely even see them in industrial plants

i'm not grabbing live phase conductors with my bare hands.
i'm not advocating doing unsafe things.

any other questions?

your reply in post #37 infers otherwise since you brought up working on delta service with no GFCIs yet havent died...

 

[mm08822]

I just wanna know if the higher current units still insta-trip when the output stage stars. I suspect they would.

Measure the current on the grd wire connected to the vfd as a starting point.

 

[u3b3rg33k]

Measure the current on the grd wire connected to the vfd as a starting point.

with a filter, measured with my fluke clamp and scope, it was under 1mA. still tripped. hence my skepticism.

 

[wyliesdiesels]

with a filter, measured with my fluke clamp and scope, it was under 1mA. still tripped. hence my skepticism.

what model fluke are you using?

brand and model of GFCI?

 

[mm08822]

with a filter, measured with my fluke clamp and scope, it was under 1mA. still tripped. hence my skepticism.

Bypass the gfci.

With vfd load at steady state, read current in both legs and the grd.

A fluke is probably giving you an rms value filtered and calculated for 60hz. You may have lost all visibility to the higher frequency components.

Scope waveforms needed from different time bases.......50hz >>>10khz.

 

[u3b3rg33k]

Bypass the gfci.

With vfd load at steady state, read current in both legs and the grd.

A fluke is probably giving you an rms value filtered and calculated for 60hz. You may have lost all visibility to the higher frequency components.

Scope waveforms needed from different time bases.......50hz >>>10khz.

i mean i use my Fluke amp clamp on my 1GHz scope. if I run without the GFCI and with a proper ground, i'll see something like 8mA on the ground (so that should trip).

if I filter the VFD, I can get it down to a measured 1mA on the ground, but the GFCI still trips. hence my curiosity. I'm hoping that these future-HF rated GFCIs are a 'solution'. whatever filtering they have in the washing machines seems to be adequate. maybe I should pick one of those filters up and see if it'll do the magic.

 

[mm08822]

What does " filter the vfd mean" exactly?

Exactly how are you measuring 1ma ?

 

[Norcal]

i see the hyperbole is still at 11.

I just wanna know if the higher current units still insta-trip when the output stage stars. I suspect they would.

also 240 delta is definitely more spicy than split phase. it's 240V to ground. there's no stinger leg. it's 240-240-240.
edit: it's grounded B.

The high leg of 240/120V delta is 208V.

 

[wyliesdiesels]

The high leg of 240/120V delta is 208V.

He meant corner-grounded 240D. No hi-leg/stinger-leg

 

[u3b3rg33k]

The high leg of 240/120V delta is 208V.

grounded B has no 120 or 208. just 240 delta.

 

[u3b3rg33k]

What does " filter the vfd mean" exactly?

Exactly how are you measuring 1ma ?

a basic X, Y setup with inductors. and a nice giant choke on the cord itself. off-the-shelf tech that's in most power supplies (but notably NOT most VFDs).

for this I was measuring off the ground.

 

[mm08822]

i mean i use my Fluke amp clamp on my 1GHz scope. if I run without the GFCI and with a proper ground, i'll see something like 8mA on the ground (so that should trip).

if I filter the VFD, I can get it down to a measured 1mA on the ground, but the GFCI still trips.

What model fluke?

How do you know there are no other ground paths?
Describe input wiring, enclosure/drive mounting, cabling to motor, motor connected to what.....all these details.

How about reading across 1, 10, or 100 ohm precision resistors placed within the egc circuit? Forget the fluke, that's what scopes are for.

 

[u3b3rg33k]

What model fluke?

How do you know there are no other ground paths?
Describe input wiring, enclosure/drive mounting, cabling to motor, motor connected to what.....all these details.

How about reading across 1, 10, or 100 ohm precision resistors placed within the egc circuit? Forget the fluke, that's what scopes are for.

it's an i400s on my rigol ds1054.

there ARE other ground paths - namely the ground, the equipment has a metal chassis.
I have not tried reading across resistors. it's been a while since i've bothered trying I switched to a code-legal "solution" - a drive on 220V lol.

 

[mm08822]

it's an i400s on my rigol ds1054.

there ARE other ground paths - namely the ground, the equipment has a metal chassis.
I have not tried reading across resistors. it's been a while since i've bothered trying I switched to a code-legal "solution" - a drive on 220V lol.

You're wasting your time measuring only one of multiple paths and with equipment that is clearly used outside of its operating range.

 

[wyliesdiesels]

it's an i400s on my rigol ds1054.

you do realize that clamp is not rated for single digit milliamps?

 

[u3b3rg33k]

You're wasting your time measuring only one of multiple paths and with equipment that is clearly used outside of its operating range.

if you give it a few turns of wire you can bump it up a scale or two. but yeah i did give up. there's only so much money in the scope instrument bucket, and I'm usually measuring in the 1-30A range.

 

[mm08822]

if you give it a few turns of wire you can bump it up a scale or two. but yeah i did give up. there's only so much money in the scope instrument bucket, and I'm usually measuring in the 1-30A range.

You would be needing more than a few turns.......on the order of 500 just to get into the bottom of the range.

 

[Innovate1]

This is something I have been involved with in design of small VFDs with included EMI filters. Response of GFCIs to higher frequencies has not been addressed in the past and some (many?) applications have not required GFCI protection but the places GFCIs are required is always expanding so seeing that this being addressed is a good thing. Have looked at a variety of GFCIs from different manufacturers and there was no consistency how they respond to high frequency.