[jjlee32]

Hey Friends,

I agree most laws here are for the birds, or lining some corporate/ bureaucrats pockets but that's a whole different rabbit hole.

I also will admit that a lot of the electrical stuff has me over my head. Looking at the breaker i have (link below) you are correct, it would only trip quickly if current is thousands of percent higher than rated, otherwise its going to take at least a minute. Is this even going to protect anything??

Generally i want to make sure I'm doing a few things things
- Make sure nothing is designed to fail or kill me if i touch it (nothing that has to comply with OSHA laws or anything, just reasonable safely
- Make sure the equipment is protected in the case of surges or large current spikes

Do you guys think that as it stands now I (moderately) safely say that? I didn't mention this but I am running a three prong 120V cord to a surge protector (a basic power strip) then that to the wall. I needed the power strip to power other 120V things like a compressor for the pneumatics on the head and the touch screen display/ RPi I am using to run LCNC.

https://www.digikey.com/en/products/...102577/1788308

Thanks again

[joeavaerage]

Hi,

Looking at the breaker i have (link below) you are correct, it would only trip quickly if current is thousands of percent higher than rated, otherwise its going to take at least a minute. Is this even going to protect anything??

You are 100% correct. Most breakers and fuses are effective inn high current fault situations but poor in mild overload conditions. 99% of our electrical system and all our appliances are designed and constructed this way
and yet it does not appear dangerous.

This sort of breaker:

https://nz.element14.com/potter-brum...tic/dp/1566490

is better for protecting circuits and equipment. They have a much better defined trip point, but note that they are not cheap and tend to be used only where required. This is for equipment protection rather
than personal safety.

Do you need such equipment to make your machine safe? I rather doubt it. Your washing machine does not threaten to kill you any time you use it does it? Why then would a CNC machine be any different?
It is when all said and done an 'electrical appliance' like any other. Provided it is designed and built in a manner similar to any other appliance then I see it posing no greater risk.

400VAC appliances attract a somewhat more stringent set of rules reflecting the increased risk should such an appliance fail in a dangerous manner. A CNC machine with coolant also deserves increased attention
with respect to electrical safety. Likewise you would be advised to keep electrically conductive swarf out of any electrical bits.....but all this is common sense which you will presumably apply in any event.

Provided you use standard wiring practices with respect to earthing and insulation requirements I see no reason to expect your machine to be electrically dangerous.

Protection against overload, say from an axis stall or a crash is another matter. Circuit breakers tend to be pretty 'coarse' protection. VFD's , servo drives and power supplies tend to have built in protection
mechanisms and they should be your first line of defence against operational faults.

Craig

PS: My Delta VFD turned up this morning. It is an 11kW unit despite my spindle being only 3.5kW (rated). It was second hand and so I bought it for about the same as I would have paid for a new
3.5kW or 5.5kW model....so I thought why not?. If I ever need to get a yet bigger spindle then hopefully this VFD would accommodate the upgrade. It is rated for 27.5A (per phase) input, but I expect to
use only a small fraction of that so I'm thinking a 20A/phase three phase D curve breaker and a 20A three phase + neutral socket/plug.

I will probably fit a DC reactor (choke)...the VFD has the terminals for it. I have an AC line reactor on my existing little Delta VFD, and very useful at noise suppression has the reactor proven to be.
I can use either an AC line reactor or a DC choke with this larger VFD. I'll probably wind my own choke.

[Al_The_Man]

Hey Friends,

- Make sure the equipment is protected in the case of surges or large current spikes
I needed the power strip to power other 120V things like a compressor for the pneumatics on the head and the touch screen display/ RPi I am using to run LCNC.

Thanks again

Maybe N.A. practices are not perfect, but when I transitioned from General industrial electronics to the inception of CNC control and retro-fits etc, some being custom PC based, Galil etc, and getting in to CNC control panel building, I looked around for a decent reference and found NFPA79, for DIY, you don't have to follow the NEC part of it, but as to earth bonding and grounding etc and other circuit practices, schematic and panel layout, it came in very useful.
The difference between an Industrial retro-fit package is that, everything is made by one Manuf. and designed to mesh together, with the onset of DIY, parts and devices are most often obtained from various sources, and also often each of these sources specify isolation etc, Device protection maybe?
But in all of my custom designs, I used the practice of earth ground all power supply commons, never had a spurious LS tripping, compared to several reports a week at one time in this forum from those that chose the contrary isolation method .!
On the subject of breakers, N.A. is slowly following the European practice of using the safety relay as a breaker,
Ensure that each of the outlets on the power strip feed a suitably sized protection device for each unit..