[SOLVED] Primary fuse will blown if secondary got shorted?

[i200yrs]

Hello All...I would like to ask something based from the attached circuit...So, let say the load from the secondary of signal transformer got shorted, can it blown the fuse at primary side? My own view it should not because they are isolated but please share your thoughts on this....thanks

 

[BradtheRad]

Yes it's possible for the fuse to blow although a transformer can be constructed with internal resistance so it hinders passing overmuch current .

 

[i200yrs]

Yes it's possible for the fuse to blow although a transformer can be constructed with internal resistance so it hinders passing overmuch current .

Ok but the primary is isolated and it doesn't have internal resistance when i measured. So do you think it can blown the fuse?

 

[crutschow]

Ok but the primary is isolated and it doesn't have internal resistance when i measured. So do you think it can blown the fuse?

Yes, depending upon the primary and secondary resistance.

What do you think determines the primary current?
The galvanic isolation that a transformer provides has nothing to do with the primary current.
The primary current is determined by the secondary current multiplied by the transformer turns ratio.

 

[i200yrs]

Alright...thanks a lot...i remember the formula... Is/Ip = Np/Ns

 

[FvM]

There are two options:
1. The fuse has been correctly chosen for the rated transformer current. Then it will surely interrupt an output short.
2. The fuse is massively oversized. Depending on the transformer impedance, either the fuse blows or the transformer burns.

 

[KlausST]

Hi,

Ok but the primary is isolated and it doesn't have internal resistance when i measured.

Where and how did you measure and what result did you get?

and especially for transformers:
* "Resistance" is one thing (measured with DC)
* "impedance" is onother thing (measured with AC)
a transformer is used on AC only.

Klaus

 

[i200yrs]

Thanks a lot to all....I managed to find the root cause of blowing fuse. The fuse connected to 4 components in parallel. The dc module, 2 signal transformers(step down), and a high voltage transformer 4800V. I isolated one by one and power-up independently. Only the high voltage transformer drawn current up to 10A. But the fuse only 3A. I made a video on my channel and share, hoping someone can learn, thanks -->