Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Replies 2 replies
  • Subscribers 35 subscribers
  • Views 99 views
  • Users 0 members are here
Options
You may also be interested in

400v single phase heating element

Scott

Hi, 

I am currently having a production line designed in China which consists of some large heating elements. One of the questions of the supplier is if the heating elements can be supplied as 380/400v single phase (using a transformer). This seems odd to me as it is not something I have came across before and not something i can find an answer on online - is this legal in the UK and is there any special signage we will require for this? 

thanks in advance.  

  • 0

    normally a resistive heater designed for 400V would be strung between a pair of phases. There is very little merit in stepping up to create a new supply of 400V L-N from a 230/400 supply.

    690 phase to phase, so  400V to ground/neutral exists in the UK as an industrial standard, normally when the site has its own substation and uses things like cranes on rails that run the full length of a big hanger so the  voltage drop over distance is an issue. 

    It is quite rare, the switchgear is quite expensive, and at the very least "caution 690V 3 phase" should be very clearly marked as such and segregated from the normal wiring.

    It is however just the next logical voltage click up from 230/400 to go to 400/690.

    It is useful if you have a lot of power to go a long way, but its not what is normally expected in the UK. 

    On a related note, even higher voltages are possible, I have, but only in a massive factory in Germany, also seen 690/1k2 - with 690V to earth/neutral and 1200V between phases. It impressive how many KVA can be sent so far on a set of cables so thin ;-) 

    I'm not sure of the regulatory position if that were done in the UK as it is above LV, while 400/690 certainly remains under normal BS7671 LV type rules, albeit the next voltage column over in the tables for ADS etc.

    In your case I'd suggest unless you have your own substation, or the power is many tens of KVA, stick to 230/400 and wire the 400V elements as a 3 phase delta.

    Mike.

  • 0

    A 400 volt heating element will work just as well if connected between any 2 phases of 3 phase, 4 wire, 230/400 volt supply, or between any phase and neutral of a 3 phase 4 wire 400/690 volt system, or from any other voltage via a transformer that gives 400 volts on the heating element.

    I would prefer to avoid transformers, as extra costs, losses and failure points are thereby added. Nothing actually  wrong with a transformer though.

    Presuming a standard UK supply, simply connected the heating elements between any two phases. If the total loading is significant, then balance the loading between phases at least approximately.

    elements between any two phases

Community Rules & Guidelines