Transformer confusion

DickCappels

Joined Aug 21, 2008
6,649
This transformer is intended to be operated at a high frequency. Unless you intend to build a switching power supply, this transformer is not what you are looking for. Even if you intend to build a switching supply, it would be hard to know whether you were using this transformer correctly by just taking guesses based on the datasheet.
 

AlbertHall

Joined Jun 4, 2014
10,558
Definitely not suitable for that purpose. The specifications are for 10kHz. The winding between pins 1 and 3 has a inductance of 839uH. That would have an impedance of around 0.3Ω at 60Hz and so would draw well over 300A from the supply. BANG!
 

gspak

Joined Sep 27, 2019
2
Could someone please help me figure out this transformer? I want to know if I can use it in a small mains-powered device. It appears that it will take AC input, but the datasheet is confusing and I can't figure out what the secondary output would be with 120AC on the primary.

https://www.taydaelectronics.com/transformer-ee19-ferrite-core.html
From the turns and the core size this is a switching transformer. If it were to operate from 120V then it would have to run at more than 200kHz and then the output would be about 5V after rectification. This is not a mains transformer but part of a switched mode power supply in a push-pull configuration.
 

Ian0

Joined Aug 7, 2020
750
Page 3 of the datasheet.
That's the hi-pot test to check the strength of the insulation. The transformer isn't operated at 50Hz to test it, in fact it won't be running at all. The test is done at 50Hz, because, regardless of the frequency of operation of the electronics, there will be a 50Hz voltage across the insulation from the mains supply, and with those results, it's only suitable if the output side is earthed.
 

Thread Starter

upand_at_them

Joined May 15, 2010
547
From the turns and the core size this is a switching transformer. If it were to operate from 120V then it would have to run at more than 200kHz and then the output would be about 5V after rectification. This is not a mains transformer but part of a switched mode power supply in a push-pull configuration.
How did you read the turns spec? I was looking at the datasheet and it didn't seem clear to me what the turns are.
 

Ian0

Joined Aug 7, 2020
750
Primary 38+37 turns
Secondary 4 turns
on page 3, section 2.
Ratio is 75:4 or 18.75:1, which is the same as 1:0.053 in Voltage Ratio Test
so for a 5V output, with 5.5V before the rectifier, it needs 103V of flyback voltage on the primary side.
 
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