How to wiring the transformer

[olaychang]

Dear sir,
Please kindly help me to check the wiring of this transformer
Thanks!

[Akita]

The turn ratio will give you the answer.

40:4:1

x2 = 80:8:2
x3 = 120:12:3
...
x6 = 240:24:6

So, if your input Voltage is 120Vac (connected to pin 1&2) then you will get 12Vac on pin 4&5, and 3Vac at pin 6&7

If your input Vac is 240Vac(connect pin 1&2) and then you will get 24Vac on pin 4&5, and 6Vac at pin 6&7

If you use Pin1&3 turn ratio should be 185:4:2

[olaychang]

but, 6&7 is short,
how can I measre the level from 6&7?

[Akita]

Basically all set of winding are shorted, but when you measure it with DMM it will create a resistance. But pin 6&7 winding is too little compare with 4&5 or 123, so the created resistance is very low, your multimeter may assume that it is shorted.

[Akita]

Sorry,..A little bit correction here
If you use Pin1&3 turn ratio should be 185:4:1

[simon5]

How do you get that 185 number between pin 1 and 3 ?

[Akita]

From the picture;

The ratio is 40:4:1
40 is for pin 1&2, 4 is for pin 4&5 and 1 is for pin6&7

At the working voltages
Pin1&2 is 78v, Pin 1,2&3 is 370v.

Because of some winding resistance the voltage will drop a bit from 80v to 78v. So, the ratio is (78:7.8:2 ) / 2 = 39:3.9:1
This is almost same as the given ratio 40:4:1

If you connect to pin 1&3, it will become 370v:7.8:2. After divided by 2 = 185:3.9:1

To make it easier to read, It will be 185:4:1

[simon5]

Thank you very much for your good explanation, I was curious.

It seemed simple, but couldn't find how to get it.