Label in an isolation transformer

Thread Starter

Rufinus

Joined Apr 29, 2020
243
Hello. I got this transformer

tr.jpg

One questión, what does the 400 mA fuse symbol mean? Does the transformer has a internal fuese or this is the fuese recomended for this transformer?

Thank you

best regards
 

MisterBill2

Joined Jan 23, 2018
18,944
It means that to assure that even a momentary short circuit will cause the fuse to open and make the transformer unuseable. I associate that with the device being a poor quality product not suitable for any use that I may have for a transformer.. Others may not agree, of course.
 

Reloadron

Joined Jan 15, 2015
7,544
One questión, what does the 400 mA fuse symbol mean? Does the transformer has a internal fuese or this is the fuese recomended for this transformer?
Figure it this way. You have an isolation transformer with a 100 VA (Volt Amp) rating so 100 / 230 = 0.4347 Amp which explains the 0.400 Amp (400 mA) fusing. Normally when transformers like this are fused it is added by the end user. Some include a fuse holder while some need you to add it. All I see in your image is the terminals on the transformer. I assume the addition of a fuse rest with you. :)

Ron
 

MisterBill2

Joined Jan 23, 2018
18,944
There are both current rated fuses and temperature rated fuses. A n internal temperature rated fuse is intended to open the circuit if an overload causes over heating, and is not an instant or fast fuse. An embedded current rated fuse is bad news.
The better quality transformer makers include an allowable temperature rise specification, and demand an external current limit fuse.
 

Reloadron

Joined Jan 15, 2015
7,544
Here are examples of what I mentioned earlier as to external current limiting fuses.

Trans Fused 1.png Trans Fused.png

Both use the typical cartridge fuse, the image on the right shows the unassembled fuse holder. These are most commonly "Control Transformers or Isolation Transformers".

Ron
 

MisterBill2

Joined Jan 23, 2018
18,944
But keep in mind that those are higher quality transformers! Produced by an honest company that can be trusted to provide correct information about their products!! I have used many of them in production machines running in auto plants. About the most reliable ones at the time.
 
Last edited:

Reloadron

Joined Jan 15, 2015
7,544
But keep in mind that those are higher quality transformers! Produced by an honest company that can be trusted to provide correct information about their products!!
Gee, and here I thought they were wound by some guy in Beijing China in his garage. Only the highest in quality and conforming to all transformer specifications. Oh well. :(

Ron
 

Thread Starter

Rufinus

Joined Apr 29, 2020
243
Thanks for all your answers.

I have emailed the company and they told me taht there is NO fuese in the transformer. This is just the recommended transforme to be installed to the final user.

Where I should intall it? in the primary or secondary?
 
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