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I am designing an in-house measurement and control system and we have decided to use a Traco AC/ DC converter. We are taking UK mains 240V AC and converting it to 12V for use in powering a number of measurement devices and an industrial PC.

I am using the TXM 035-112 AC/DC converter which means the AC must be wired to the AC/DC converter rather than using a kettle lead, (UK Mains plug to C13 IEC Socket). It works fine, there are no problems but I am concerned in case we are not complying with the UK electrical safety standards, (e.g. Do we need to earth the control system chassis? Is an MCB required? Do I need to place electrical hazard stickers)

Does anyone know the standards that must be followed when using screw terminal AC/ DC converters? (We have been referred by SteveG & Traco to IEC 60950-1 (£620) which we don't yet have, (why do safety documents cost so much?).

Ideal would be an xyz of what needs to be done according to EU law.

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  • \$\begingroup\$ UK mains is 240 V AC, not 24VAC. You might want to explain "kettle lead" for the international audience and provide links to the PSU datasheet. \$\endgroup\$ – Transistor Sep 1 '16 at 17:44
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There are electrical safety standards that must be followed for your product as a whole. These are usually EU standards rather than UK standards. Unless there is a product specific standard you probably should use EN60950 and all of its amendments. I'm not aware that there is a specific standard for using a an AC/DC module, its use will be covered in the main standard.

It is difficult to give advise about the safety of your product without a sample of the product and a thorough knowledge of how it is intended to be used. And anyway this site is not meant for that. You asked a few specific questions:

Do we need to earth the chassis?

You should must earth the chassis of the AC/DC module. This is for both electrical safety and EMC. The earth connection is often used to absorb high frequency interference coming from the AC/DC module, and also to absorb high energy transients going to it. Generally you must also earth the metal chassis of your product.

Is an MCB required?

Usually, no. However, you should use a glass fuse in the Live conductor. Most people would use a Fused Terminal Block for the mains connection.

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Do we need to earth the chasis?

Pin 3 on these modules has a protective earth symbol on them: -

enter image description here

This means it must be earthed. I would also advice you to read the data sheet and follow the link on page 3 that takes you to the certification documents - these should give a fuller indication of YOUR obligations when using your particular model.

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  • \$\begingroup\$ apologies, I meant to state the control system chassis not the AC/DC converter. \$\endgroup\$ – SeanJ Sep 1 '16 at 18:37
  • \$\begingroup\$ Does the traco have a metal base that is attached to your main chassis for cooling purposes? \$\endgroup\$ – Andy aka Sep 1 '16 at 18:52
  • \$\begingroup\$ the traco supply is connected to a mounting plate which is connected to the chassis and hence grounded. The grounding is an example. For example if I do 4 of the 5 required things and someone injures themselves, that is not good. I need to have all the t's crossed and i's dotted. Sorry for not stating this sufficiently in the first post. \$\endgroup\$ – SeanJ Sep 1 '16 at 19:00

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