4160V Motor Surge Capacitor Replacement
4160V Motor Surge Capacitor Replacement
(OP)
Replacing some PCB containing surge capacitors in a 4160V compressor motor termination box. Contractor reccomends replacing the short length of cable also. Here's our dilema the existing cables are non sheilded. If we replace this short length with sheilded cable as required by the current code what should we do with the sheilds? The existing motor feeds from the gear are un sheilded and are not being replaced. Picture is attached for reference






RE: 4160V Motor Surge Capacitor Replacement
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 4160V Motor Surge Capacitor Replacement
RE: 4160V Motor Surge Capacitor Replacement
I think what it shows is this:
- 1- Supply current enters through three single phase round brown insulators or bushings at bottom of the picture.
- 2 -Unshielded cable goes from insulators to a 3-phase rectangular grey surge cap unit. Motor T-leads (shown at top of picture) are also landed on the same surge cap unit and are unshielded (like all motor T-leads).
- 3 -The insulator/bushing has an inside-TB terminal where this unshielded lead is connected, and another outside-TB terminal which connects to a cable that has been terminated with a stress cone. (?)
Are 1, 2, 3 correct?At any rate, there are no stress cones inside the box and everything looks unshielded, so I don't see how you could add any shielded cable (need a stress cone at each transition between shielded and unshielded).
Even if this were a new installation, what kind of code requirement would you to install require shielded cables if they run completely inside a term box? All such cables are unshielded in my experience (we rely on proper training of unshielded leads inside the terminal box to prevent stress concentration from close contact to sharp metal corners). Note if you had partial discharge pd coupling capacitors in the termbox, the tapoff cable for those would be unshielded as well.
=====================================
(2B)+(2B)' ?
RE: 4160V Motor Surge Capacitor Replacement
=====================================
(2B)+(2B)' ?
RE: 4160V Motor Surge Capacitor Replacement
And my Early's Handbook states that the 2400v exception used to be 8kv exception.
So this is supposed to apply to jumpers inside terminal boxes (for new installations)? Has anyone seen a shielded jumper running completely inside a term box?
=====================================
(2B)+(2B)' ?
RE: 4160V Motor Surge Capacitor Replacement
=====================================
(2B)+(2B)' ?
RE: 4160V Motor Surge Capacitor Replacement
What I think you are seeing at the bottom of the picture are older style spark-gap style surge arresters. The Surge Caps and Surge arresters are part of the surge pack that comes all pre-wired when you purchase the surge pack. I have even seen bare conductors/links between the cap and arrester - see attached photo. Maybe that can help clear up some questions. I would try to replace the entire surge pack and not just the caps, but in any case I do not see a reason for using shielded cable and would even doubt that you can with such short jumpers.
"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic — and this we know it is, for certain — then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". – Nikola Tesla
RE: 4160V Motor Surge Capacitor Replacement
Sounds like unanimous opinion that it doesn't make any sense to install shielded jumpers inside a terminal box.
=====================================
(2B)+(2B)' ?
RE: 4160V Motor Surge Capacitor Replacement