Signal wires for ac drive. 2

[Thedroid]

I'm installing a small frequency drive to run a grinding aid pump for a large ball mill. I need a 4-20 mA signal to the drive to control the speed, and another 4-20mA signal back to a plc for current feedback. I have a shielded cable that's already in place that contains two twisted pairs. I'm wondering if this cable is adequate or do i need two pull another one where each pair is individually shielded. Wire pulls in the mill building can be pretty ruff with all the dust and transitions from cable to tray.

This is my first post, I'm an Electrician and Instrumentation tech at a cement plant. I'm looking forward to being a part of this forum.

 

[ScottyUK]

I think you will be fine with the cable you have under most circumstances. In your favour there is an overall screen and the pairs are twisted. Indvidual screens are to prevent crosstalk between signals but the type of signal you have isn't likely to generate much in the way of crosstalk. Both mA signals will change at relatively low rates so the possibility of coupling between pairs is small.

Welcome to the forum BTW.

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If we learn from our mistakes I'm getting a great education!

 

[ozmosis]

Thedroid
I would agree with Scotty. Keep your cables away from the motor cables where possible, but if you have to cross then cross at 90deg.

 

[Thedroid]

The motor cables are going a different direction. The signal cable will be going in a tray with other signal. I figured it would be alright, but I thought I would ask. I'll test it tomorrow if the motor comes in.