CE/European Control circuits

[devittjl]

Looking at IEC 60204 9.1.1 states that where control circuits are supplied from an ac source control transformers shall be used.

Typically on a 380-415V+N supply I will pull my 220-240Vac single phase by using a one of the phases + N.

Looks like I cannot do this.

Can anyone with experience with CE standards and CE wiring practices for industrial equipment comment.

Particular equipment is a small conveyor oven rated for 18A @415VAC which will be located in a supermarket bakery.

Thanks in advance for any help

 

[itsmoked]

I've seen it done but in my opinion NOT using an instrument transformer is cheap, dangerous, and a bad practice in the 380V+ realm.

The instrument transformer is a perfect place to shave off noise spikes. It provides some serious impedance to protect the system during faults. It isolates your controls from the mains. It allows you to establish a new neutral. They can be had for pocket change. A lot of them come with integral fuse blocks to provide SC/OVLD protection.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[dpc]

480 V control voltage is still allowed by NEMA in the US, but it's a really bad idea whose time should be over and done with. I have no idea about IEC requirements, but I wouldn't do it at 380 V either, for all the reasons that Keith gives.

With the increased concern regarding arc-flash, control voltages are trending down, not up. There's a real push in some industry segments to run MCCs and all machine tool controls from 24 V dc.

I'd put the transformer in.

 

[ScottyUK]

Most 415V gear uses a 415/110V transformer to provide a local control supply. One end of the secondary is earthed to the frame. On smaller control gear 24V DC is becoming popular for safety reasons although 110V AC is more common where larger contactors are employed. I'd be very unhappy with a control supply fed directly from a 415V line: the control transformer reduces the available fault current down to a low level. This is the 'arc flash' hazard referred to above.


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

 

[benta]

Looking at the OT, it seems that he's working with a three phase 400 V (European) system, in that case with 230 V phase-neutral. Or am I reading this wrong? Please clarify, devittjl.

Benta.

 

[ScottyUK]

I agree, but 230V from a typical industrial system is capable of a) killing you b) blowing a bloody great hole in whatever it faults to. A control supply from a small transformer is less likely to do a) and can't do b).


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

 

[devittjl]

Yes benta, I am using a 3 phase 400V system. Control voltage is 230v by using a phase-neutral connecton.

What I need to know is this prohibited by codes/standards in European community (and UK specifically).

Control voltage will most likely be 230v whether I use a transformer or not. That is standard for my company/equipment.

 

[ScottyUK]

I don't believe it is prohibited by any regulations, but it is a bad practice and there is no excuse for it except to save money.



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

 

[itsmoked]

Sadly it is very common in refrigeration equipment. The apex of cheap.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[panelman]

We do panels for various sectors in the UK.

Water industry tends to be 110V for simple stuff and 24V DC for stuff with plc controls.

HVAC tends to be 24V AC if we choose or 240V if we have a mean client in the mood to choose

Mechanical handling (food factories, newspapers and distribution centres) tend to be 24V DC

Obviously other peoples experiences may vary