Browse FAQs

Is it necessary to use shielded wire on the STOA, STOB terminals on the Altivar Process drives?

Published date: 10 June 2020

Altivar Process Drives using shielded wire on the STOA and STOB terminals.

Product Line:
Altivar Process drives, ATV600 and ATV900 series

All models, All serial Numbers

Installation manual shows that shielded cable is mandatory but customer is questioning if this is correct.

It is necessary to use shielded cable on the STOA / STOB terminals in order to meet SIL level 3 requirements.

If there is damage to the insulation on an unshielded cable, the potential exists for an external source of power to come in contact with the conductor of the wire connected to the STOA and/or STOB terminals, which could interfere with the normal operation of the safety circuit.   For this reason, it is necessary, in order to meet  SIL level 3 requirements, for a shielded cable to be used with both ends of the shield grounded.  If the insulation of this wire is damaged, it is likely that any external source of power will make contact with the shield first and be shunted to ground before making contact with the conductor and potentially interfering with the safety function.  Note: It is possible for a ground loop to be created by connecting both ends of the shield to ground.  If this happens, it is acceptable to connect the shield to ground on the drive side only.

Was this helpful?

What can we do to improve the information ?

Can't find what you are looking for?

Reach out to our customer care team to receive information on technical support, assistance for complaints and more.