OT shielding

ivo.maenen · Jan 20, 2008

Somewhere I have read that you don't need to shield the powercable between a softstarter and the motor. But I'm thinking that even the limited time for ramp-up or ramp-down is creating problems for other electronic components e.g. communication, so you would need to shield it.

I have no experience with softstarters and every topic in this forum is about shielding invertors. So how do the people who do this every day think about this? What do you do?

surferb · Jan 20, 2008

You'll want to run your data (copper) cables away from there even if it's shielded, which I think is always a good idea, safety permitting. If it's not, make sure you don't have any potential crosstalk issues. I've dealt a lot with cabling, but not softstarts. Does anyone know how powerful a field they induce?

ivo.maenen said:
Somewhere I have read that you don't need to shield the powercable between a softstarter and the motor. But I'm thinking that even the limited time for ramp-up or ramp-down is creating problems for other electronic components e.g. communication, so you would need to shield it.

I have no experience with softstarters and every topic in this forum is about shielding invertors. So how do the people who do this every day think about this? What do you do?

KP_EENG · Jan 20, 2008

A couple of months ago I added a softstart in an existing control panel to start a CIP pump and did not run sheilded cable to the motor, but the precuations that I did take were to run the motor leads to the motor in a separate 3/4" rigid conduit and where the leads did have to cross some I/O wiring in the panel I made sure that it crossed perpendicular to the I/O wire bundle to limit any effects of noise. To date, we have not had any problems with noise.

regards

DickDV · Jan 20, 2008

I've never encountered a situation where an SCR-chopper softstarter produced enough EMI-RFI interference to affect any adjacent controls.

An SCR chopper doesn't produce particularly high frequency harmonics which probably is a large part of their being rather trouble-free.

Gil47 · Jan 21, 2008

DickDV summed it up in my view.

Our case, we have 2, 500 Kw motors, 800 Amps on soft starters, using 400mm conductors (3/4 square inch) as 3 single core cables, We placed these conductors, cable tied together, this way the resultant current flow around the 3 phase conductors is zero, the control cables are run in a another bunch seperated where possible.

ivo.maenen · Jan 22, 2008

Thanks for your input!

If somebody else wants to comment, please do so.

JesperMP · Jan 22, 2008

We are on some projects running 100+ meters of cable between a 100kW softstarter and motor. No shielding, but as always motorcables and signal cables are separated from each other whereever it is practical.

Tom Jenkins · Jan 22, 2008

We've never had a problem with soft starts and normal wiring practice. Remember, with a good soft start the bypass contactor pulls in once the motor is up to speed and the SCRs no longer carry the load. If you did have crosstalk it would be transient in nature.

OT shielding

ivo.maenen

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surferb

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KP_EENG

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DickDV

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Gil47

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ivo.maenen

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JesperMP

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Tom Jenkins

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