infolinks

News

Circuit-breakers inside LV Switchboards

Dissipation of the heat generated inside switchboards


After an analysis of the main heat sources and of the measures to limit heat generation, the modalities through which switchboards can dissipate the heat towards the outside are described now. Many of these considerations derive from the Std. IEC/TR 60890, which gives formulas and tables where constructional characteristics and installation modalities are in relation with the temperature-rise at the same power loss. In particular, this article shall take into consideration the switchboard ventilation, the surfaces of the switchboard and their positioning, the form of internal separation of the switchboard and the degree of protection of the switchboard. 






2.2.1 Switchboard ventilation 


To increase the switchboard cooling, it is important that a good circulation of air inside the switchboard is realized  and maintained. To this purpose, for example, the possible ventilation openings are to be properly dimensioned and positioned. As regards dimensioning, IEC/TR 60890 for temperaturerise assessment inside low voltage switchgear and controlgear assemblies prescribes for the enclosures with ventilation openings that the cross section for air outlets is 1.1 times the cross section of the inlets. This requirement is due to the greater volume of hot air (going out of the switchboard) in comparison with the cold air (going into the switchboard). When disregarding this prescription, the air inlet surface of the switchboard is not fully exploited. 

As regards the positioning of the ventilation openings, these are to be located so that the “draught chimney” effect is achieved: an opening shall be positioned at the bottom of the switchboard, on the front part, the other one shall be positioned at the top, on the rear part, or on the “roof” of the switchboard. It is important to remind that any openings at mid height could reduce the “draught chimney” effect, thus causing a reduction of the air “draught”. The equipment inside the switchboard shall be positioned so that the circulation of the air is not excessively impeded by a reduction of the section for the air flow. In case of withdrawable circuit-breakers, particular attention shall be paid to prevent the obstruction of the ventilation openings in the fixed part of the circuit-breaker . 


2.2.2 Side surfaces and positioning of switchboards


 It is necessary to take into account that a switchboard exchanges heat with the surrounding environment through its surfaces (top, bottom and side walls) and therefore, at the same power dissipation level by the internal components, the larger the exchange surface towards the outside and the better the exchange conditions depending on the installation modality are, the greater amount of heat is released. For example, the switchboard should be positioned so that the air circulation around its external surface is facilitated or, however, is little impeded, thus improving heat exchange. IEC/TR 60890, which, as already said, suggests a method for the temperature-rise assessment inside switchboards, does not consider the real external geometric surface of the switchboard, but introduces the concept of effective cooling surface “Ae”, intended as the sum of the individual surface areas (top, front, side, ....) “A0 “ multiplied by the surface factor “b”. This factor takes into account the heat dissipation of the individual surfaces according to the type of installation of the enclosure, that is the different capacity of dissipating heat according to the surface positions and to their being either exposed or covered. The values of the parameter “b” related to the different surface types are shown in the table below .

                                                                     Ae =∑ (A0 x b)




2.2.3 Forms of internal separation of switchboards 


With separation form it is meant the type of division provided for the different circuits inside the switchboard. Separation is obtained by means of metallic or insulating barriers or partitions. For further information about the different forms of separation reference shall be made to the  prescriptions of Std. IEC 60439-1. As evident, remarkable separation forms tend to limit air circulation inside the switchboard, thus affecting the temperature inside the switchboard itself. 



2.2.4 Switchboard protection degree 


The degree of protection IP shows the protection of the enclosure against access to hazardous parts, against ingress of solid foreign objects and ingress of water. The code IP is the identification system of the degrees of protection based on the prescriptions of the Std. IEC 60529. The degree of protection of a switchboard affects its capacity of dissipating heat: the higher the degree of protection is, the less heat is dissipated by the switchboard. Therefore, the choice of high degrees of protection is not recommended when they are unnecessary. Besides, it should be kept in mind that a defined degree of protection may be reached through different modalities. For example, the protection against the vertical fall of drops of water (IPX1) can be realized by such modalities so as not to affect heat dissipation and so as to keep the “chimney effect” inside the switchboard. 

This article has been extracted from circuit-breakers inside LV switchboards by ABB 

Download the free guide here
  





32 comments:

  1. Through this post, I know that your good knowledge in playing with all the pieces was very helpful. I notify that this is the first place where I find issues I've been searching for. You have a clever yet attractive way of writing. tổng đài ảo fpt

    ReplyDelete
  2. I got too much interesting stuff on your blog. I guess I am not the only one having all the enjoyment here! Keep up the good work. irf540 replacement

    ReplyDelete
  3. As soon as I found this web site I went on reddit to share some of the love with them. high voltage testing in Pakistan

    ReplyDelete
  4. Wonderful article. Fascinating to read. I love to read such an excellent article. Thanks! It has made my task more and extra easy. Keep rocking. BizOp

    ReplyDelete
  5. Very informative post! There is a lot of information here that can help any business get started with a successful social networking campaign. 온라인릴게임

    ReplyDelete
  6. I’ve read some good stuff here. Definitely worth bookmarking for revisiting. I surprise how much effort you put to create such a great informative website. 토토커뮤니티

    ReplyDelete
  7. Thankyou for this wondrous post, I am glad I observed this website on yahoo. 안전놀이터

    ReplyDelete
  8. I have read your article, it is very informative and helpful for me.I admire the valuable information you offer in your articles. Thanks for posting it.. 대전스웨디시

    ReplyDelete
  9. I am impressed. I don't think Ive met anyone who knows as much about this subject as you do. You are truly well informed and very intelligent. You wrote something that people could understand and made the subject intriguing for everyone. Really, great blog you have got here. 대전1인샵

    ReplyDelete
  10. An fascinating discussion is value comment. I think that it is best to write extra on this matter, it won’t be a taboo topic however generally people are not enough to talk on such topics. To the next. Cheers รักษาสิว

    ReplyDelete
  11. I can’t imagine focusing long enough to research; much less write this kind of article. You’ve outdone yourself with this material. This is great content. 토토사이트

    ReplyDelete
  12. I am unable to read articles online very often, but I’m glad I did today. This is very well written and your points are well-expressed. Please, don’t ever stop writing. 먹튀검증

    ReplyDelete
  13. I really appreciate this wonderful post that you have provided for us. I assure this would be beneficial for most of the people. 토토커뮤니티

    ReplyDelete
  14. Thanks for posting this info. I just want to let you know that I just check out your site and I find it very interesting and informative. I can't wait to read lots of your posts. 토토커뮤니티

    ReplyDelete
  15. That is the excellent mindset, nonetheless is just not help to make every sence whatsoever preaching about that mather. Virtually any method many thanks in addition to i had endeavor to promote your own article in to delicius nevertheless it is apparently a dilemma using your information sites can you please recheck the idea. thanks once more. 먹튀검증

    ReplyDelete
  16. Thankyou for this wondrous post, I am glad I observed this website on yahoo. 먹튀폴리스

    ReplyDelete
  17. I am very happy to discover your post as it will become on top in my collection of favorite blogs to visit. 먹튀검증

    ReplyDelete
  18. Wonderful blog! I found it while surfing around on Yahoo News. Do you have any suggestions on how to get listed in Yahoo News? I’ve been trying for a while but I never seem to get there! Appreciate it. 먹튀폴리스

    ReplyDelete
  19. i love reading this article so beautiful!!great job! 대전마사지

    ReplyDelete
  20. I wish more authors of this type of content would take the time you did to research and write so well. I am very impressed with your vision and insight. SEO SERVICES IN DELHI

    ReplyDelete
  21. Thankyou for this wondrous post, I am glad I observed this website on yahoo. toryburchoutlet.org

    ReplyDelete
  22. thank you for your interesting infomation. 바둑이

    ReplyDelete
  23. I have read your blog it is very helpful for me. I want to say thanks to you. I have bookmark your site for future updates. 온라인바둑이

    ReplyDelete
  24. Awesome dispatch! I am indeed getting apt to over this info, is truly neighborly my buddy. Likewise fantastic blog here among many of the costly info you acquire. Reserve up the beneficial process you are doing here. 토토사이트

    ReplyDelete
  25. Thanks for writing such a good article, I stumbled onto your blog and read a few post. I like your style of writing... 토토사이트

    ReplyDelete
  26. I definitely enjoying every little bit of it. It is a great website and nice share. I want to thank you. Good job! You guys do a great blog, and have some great contents. Keep up the good work. detectives privados en barcelona

    ReplyDelete
  27. I am definitely enjoying your website. You definitely have some great insight and great stories. detectives privados barcelona

    ReplyDelete
  28. Positive site, where did u come up with the information on this posting?I have read a few of the articles on your website now, and I really like your style. Thanks a million and please keep up the effective work. 토토사이트

    ReplyDelete
  29. If you are looking for more information about flat rate locksmith Las Vegas check that right away. 토토사이트

    ReplyDelete
  30. howdy, your websites are really good. I appreciate your work. 꽁머니 지급

    ReplyDelete
  31. Pretty nice post. I just stumbled upon your weblog and wanted to say that I have really enjoyed browsing your blog posts. After all I’ll be subscribing to your feed and I hope you write again soon! 먹튀검증

    ReplyDelete
  32. Interesting and amazing how your post is! It Is Useful and helpful for me That I like it very much, and I am looking forward to Hearing from your next.. 토토사이트

    ReplyDelete