I got this Hammond 500VA Isolated Transformer.


It's 500W capacity.. and I'm only using 30W. How come the temperature already reaches 50 Celsius (122 Fahrenheit)?

How about you? What temperature did you measure you transformer? And what is the load and capacity?

Is it not when a transformer only has light load. It shouldn't get hot? Or does it run hot even with no loads?

Lastly, is an Isolated Transformer hotter than an Autotransformer equivalent?

  • 1
    Keep in mind that without at least modestly effective passive cooling (fins) and some airflow, something like this retains heat fairly well. That means that even a small energy inefficiency can build up over time to raise the temperature significantly. It doesn't necessarily mean it's pouring out wasted energy.
    – isherwood
    Oct 25 '18 at 13:06
  • 1
    i have lot of older transformers (wall worts) that run warm even if nothing is plugged into the output. if the temp doesn't go way up when you draw 60w instead of 30w, it's probably just a base-level heat overhead.
    – dandavis
    Oct 25 '18 at 16:21
  • This guy is a total scammer asks new questions based on no knowledge and argues answers with no up votes on more than 10 answers that are 100% not only from me but others that are pros,
    – Ed Beal
    Nov 22 '18 at 2:48
  • Because when I first joined.. I couldn't up vote... beginners at stack exchange can't up vote.. it's only now that I'm aware I can up vote already... and I just upvoted the answers by Ed and others (3 hours ago). And I don't know comments should be upvoted too (I upvote comments now).
    – Samzun
    Nov 22 '18 at 2:59
  1. Most transformers will give off heat. I don't know if 50C is too hot but most transformer components are rate either 75C or 90C. I suppose you could give Hammond Manufacturing a call and ask their engineering department.

  2. A simple transformer is basically two coils so your primary side is always passing current. Due to that you have a lot of EMF or Magnetic opposition which is the cause of the heat. I won't get more involved in transformer technology since it is about a one semester course and I don't want to bore you or myself to death by trying to explain any more than I have. I will say it does rise in temperature under heavier loads.

  3. An autotransformer will also give off heat. Your particular transformer is shielded and for that reason probably will give off more heat and it is an isolation transformer, and an autotransformer is not. So really not comparable.

Hope this helps

  • So if I need to put the transformer inside a metal panel box.. and avoiding very hot transformer, then I should just get an autotransformer of the same wattage, right? Maybe autotransformer gives off 50% less heat? What is your estimate?
    – Samzun
    Oct 25 '18 at 13:07
  • @Samzun - No estimate and no recommendation, but looking at its cut sheet it doesn't appear to be a transformer that is mounted inside a metal panel box. Why don't you just replace it with a duplicate of whats there now? Oct 25 '18 at 13:21
  • It's not yet build. I will put 220v-110v transformer to power a 120v Surge Protector Device type 3 to avail of lower clamping voltage. 240v would have higher clamping voltage than 120v. I will put all of these in empty panel box because it's a public place and I can just put them in the open or they can be stolen within days. But since autotransformer has much less winding.. then it's really less hot. right?
    – Samzun
    Oct 25 '18 at 13:27
  • 1
    @Samzun - No, an autotransformer is different than an isolation transformer. Heat gain in this situation is not relevant to size. In fact may be just the opposite of your thinking. I might try a heat sink instead. The basic problem is that I don't think you can provide enough information for stackexchange to answer your question unless you rewrite you questions (I have seen your other post), and provide some more detail about the entire electrical specification requirement. Oct 25 '18 at 13:44
  • I know the difference between an autotransformer and an isolation transformer. Which of them has heat gain not relevant to size? Or just the opposite of my thinking? Are you referring to autotransformer or isolation transformer? Please clarify a bit about heat gain in each of them. Thanks.
    – Samzun
    Oct 25 '18 at 13:48

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