Terminating Festoon Cable Shields

[murphy625]

Any suggestions on how to terminate Shields for a flat cable?
If you look at the link to the photo, I have to go threw 2 of these boxes. (One for each side of the festoon cable system)

The left side are all power (480 volts).
The right side is all DC and resolver cable.
Notice the 2 white cables.. They are shielded motor leads for the servo and another motor.
The red lines are 480 volts to a brake.
The red and white are 110volts to a signal light.
The Blue is 24vdc to limit switches.
The large black one on the right side is the encoder.

All this has to go threw those 2 yellow flat festoon cables. Any suggestions for attaching all these Shields in a professional manner? No one seems to make any devices for this. Also, should I tie the festoon cable sheilding to the encoder sheilding? What a mess eh?

The green wires are temporary grounds for testing.
And as I understand, it would be a good idea for me to shorten up my pigtail leads to the terminals. (will be working on this)

Full Size Picture at this link:
http://www.andersongmd.com/PaulAndOl...203%20copy.jpg

Thanks!!!!
Murph

[ViperTX]

The pig tail length is okay, the shielding is for stuff that is outside the box (metal box). For terminating the shields, I would put them in a giantic ring terminal and use a #10 screw with lock washer....gotta remove the paint so the shield is indeed grounded.

[murphy625]

I am worried that the high frequency coming from the servo drive 480v power lines (and later one of those large cables will be from a vfd drive) may radiate to the encoder wires if I leave to much unsheilded pigtail. (as was suggested in another thread).

The juntion box you see is NOT grounded to equipment frame as this part of the equipment rides on 4 rubber wheels and has no metal connection to frame.
Should I just tie all the sheilds together and use them? or should I sacrafice one of the festoon wires for use as a frame ground connection and then run all the sheilds to the box wall. ?

Its been an interesting project..

Thanks
Murphy

[sbrpollock]

Murphy:
I've installed some German built equipment that had a method of dealing with this. The terminal strip had a copper bar running the length of it just in front of, and just below where the wires go into the terminal strip. All I had to do was strip just enough of the insulation and shielding off to put the wire in the terminal strip. The shield layed across this copper buss bar. The ones I used had special clamps that were then applied that held the shield firmly against this buss bar.

It made for an extremely neat instalation, and left no more than about an eighth to a quarter of an inch of cable unshielded.

I don't know if you can picture what I'm talking about. I'll try to find a picture on the web somewhere.

[sbrpollock]

This is similar to what I used. The ones I used had the buss bar closer to the terminal strip, but you get the idea.

[ViperTX]

Well what you would theoretically like to create is an uninterrupted shield from end to end. The box where the cables enter is part of the shield it does not need to be grounded to work as a shield...it must just be part of the shield. So the box being metal you enter it....tie your shields to it....you exit the box your shields are tied to the box and then you get to the termination point (like the controller or the end machine) and the shields are tied to that point.

[sbrpollock]

In my application; The idea was to shield the cable from sources that were "inside" the enclosure. The enclosure only shields against sources that are on the outside.

[murphy625]

Originally Posted by sbrpollock In my application; The idea was to shield the cable from sources that were "inside" the enclosure. The enclosure only shields against sources that are on the outside.

Yes.. Same here...

Those wires on the left side of that picture are all 3phase 480 volts. One is from the servo motor, the other is just a normal 3 phase line but it will soon be powered by a VFD.

I've been doing a bunch of reading. (like around 10 hours last night) Another thread I started in this forum was dealing with a ground loop. I learned many things that I already know.. LOL Just never realized how important some things can be in this application.

Im going to use the ground bar infront of the terminal strip idea. I have some copper bar stock I can drill and tap.
Is it really required in this type of installation to use that 360 deg clamp technique??

Thanks for all the advice !!!

[sbrpollock]

One of the ways I've seen this done is to drill a series of holes along the lenght of the ground buss bar. (So you end up with a hole on each side of each wire) Then, use wire ties through these holes to clamp the shields against the bar.

[murphy625]

Originally Posted by sbrpollock One of the ways I've seen this done is to drill a series of holes along the lenght of the ground buss bar. (So you end up with a hole on each side of each wire) Then, use wire ties through these holes to clamp the shields against the bar.

Wire ties?? The only wire ties I am familiar with are the nylon ones...

A metal wire tie??

[sbrpollock]

Yes Nylon Ties. The sheild is only grounded where it makes physical contact with the buss bar. The nylon tie just holds it against the bar. It doesn't provide the full 360 deg connection that the clamps in the photo above provide. But I have seen it done that way in some of the cabinets I've worked in, and it did seem to work well.