Thread: earthing a water cooled spindle

I used this cable, for my 800wt air cooled spindle. I've solded the shield to the fourth cable, and use this cable for my earth, which also ties the shield to ground. I don't have conductive motor mounts, so I have solded the cable to a hose clamp, which is clamped onto the spindle. If you have aluminium motor mounts, then you could screw the earthing cable to the mount.

I would use a larger cable at least 1mm2, or larger for bigger spindles, as the shielded cable you suggest is a little light for the spindles. The 800watt spindles run on 7 amps and can go higher with a sudden load.
Of the ten or so spindles I have brought they all have the same virtual earth. Definately earth the spindle and the machine and more important with a water cooled jobby.

Hi Rod,
have you a link to the cable that you would use.

Kiwiken

Hi Ken,
Ausxmods sell the cable I have used but he looks like he doesn't list it anymore or is out of stock.
It is a 4 core shielded cable. Seafurymike posted a link in another thread to cable that looks suitable here.

I thought the wire that chrisb691 linked to looked a bit thin at 22 gauge. I figured 20 gauge at least.
I've some 3 phase cable that will suit but it's too big to go in the plug to the spindle and probably won't fit down the cable chain.

It may well look undersized, but on my 800wt air cooled spindle it doesn't even get slighly warm to the touch. To me, at least, this indicates that it is running well within it's current capacity. Of course, I have been known to be wrong before.

Try DKSH and the Olflex cables made by LAPP. These are designed for such applications and come in a range of AWG sizes and core numbers. As Rod mentions 1.0mm^2 (18AWG) will cover roughly 10A and is a good range to start with.

As for an 800w spindle running on 7A i am not sure. The power formula is P=IV which means current should be 800w / 240vac = ~3.5A. Well under the rated current capacity on the 22AWG wire, which is why it shouldn't get hot.

Daniel

*EDIT - I Would not personally use 22AWG wire though.

Originally Posted by rodm

Hi Ken,
Ausxmods sell the cable I have used but he looks like he doesn't list it anymore or is out of stock.
It is a 4 core shielded cable. Seafurymike posted a link in another thread to cable that looks suitable here.

Yea all gone, I do have an off-cut in storage if anyone wants it, just take care of shipping and its yours but from memory its only a few meters long. It's a 4 Core 1.0mm2 80% Shielded.

I've also used cablesplus.com.au to rebuild a chinese machine, but the Siemens 4C1.5mm2 may be too thick and stiff to fit in the cable chains of the small chinese machines, they were able to send me a sample of 0.75mm2 but I'm not sure if they stock this size to sell per/m.

I would have also gone with some 1.0mm2 cable for the spindle but thats just my personal opinion, maybe its best to ask a sparky or a cable supply company like Cablesplus what they recommend I would have thought 22 Gauge is too small.

Hope this is not to late just saw this thread.
Here I a link to my spindle story, it also cover new plug and wire
Hope it's a help
https://www.woodworkforums.com/f170/w...sembly-136209/


Russell

Originally Posted by snowyskiesau

While waiting for some bits to finish off the new controller, decided to look at the spindle wiring as the supplied cable is too short to route via the cable chain.
There are only 3 wires in the cable - no earth, Not sure if this is common or it's just me.

..............
Any thoughts on this? What do others do for an earth solution?
If this is a good idea, what cable is recommended?

I do not understand the need to provide an earthing point on the spindle motor.
The motor does not need an earth to operate.
There is no safety advantage because the three phases are floating and there is no return path to earth for stray currents.
Shielding should only be earthed at one end. This should be a single point connection common to any other shields. Otherwise a path is set up for current flow in the shielding (earth loop) which can induce the interference it is meant to reduce.
Regards
Peter.

Originally Posted by WoodPleb

I do not understand the need to provide an earthing point on the spindle motor.

It's called a protective earth for a good reason. It may not be required to make the motor function, but is should certainly be there for when the motor decides to malfunction i.e. one or more phases short to the body of the spindle

Shielding should only be earthed at one end. This should be a single point connection common to any other shields. Otherwise a path is set up for current flow in the shielding (earth loop) which can induce the interference it is meant to reduce.
Regards
Peter.

Agreed, shielding should be earthed at one point, in my case the controller.

Originally Posted by rusel

Hope this is not to late just saw this thread.
Here I a link to my spindle story, it also cover new plug and wire
Hope it's a help
https://www.woodworkforums.com/f170/w...sembly-136209/


Russell

Never too late for useful information! I'll file this one away hoping I never need it

Got the cable today so next stop, add an earthing point in the spindle.

I thought I'd do it by drilling out one of the tapped screw holes used to mount the existing socket and add a longer screw that has a nut on the end to hold the earth wire.
All depends if I have a small enough/long enough screw in the collection.

The new wire is going to be too thick to put in the cable chain once the cooling tubes are added so I'll need to work out some way to anchor that as well.

Firstly this is my first post on this forum and I hope I'm not butting in here.... but as an automation engineer with many VFD installations under my belt (around 300 and counting) I feel I should clarify a couple of things about VFDs

I see that everyone is convinced that the sheild should only be connected at one end. This is a common misconception held because it is common practice to do so with instrumentation in order to reduce earth loop interference. In the case of VFD's though the purpose of the sheild is to keep the noise in and return it to it's source (the drive). Although the VFD's base frequency may be anywhere between 0 to 400hz the actual carrier frequencey can be between 2 and 16 Khz depending on the drive. This causes a large amount of RF to be generated causing interference to electronics etc.The best way to contain this noise is to connect the sheild at both ends.The drive will generally have an earth terminal on the gland plate at the bottom of the drive. Connect your sheild here and then connect the drives protective earth to the same terminal.

The purpose of the protective earth is two fold the first as a "protective earth". The output of the drive will have a potential to earth so if you break a wire (which is bound to happen on a flexible application) you want the protection to work and not liven up the frame of your machine. The second use for the earth is to try and divert any stray RF currents that are trying to find their way back to the drive. These currents have a nasty habit of travelling through your spindle bearings and greatly reducing their life.

The best cable for flexible vsd applications is IGUS chainflex available from Treotherm trading in Sydney and they usually sell by the metre. You can also ask your local Auslec to get it for you but as with all good things it's not cheap! Olflex / Lapp cable are also good choices. Just make sure it's flexible.

I hope this helps

Paul