Hello, all:

So I have to deal with transformers for my project. From my understanding, a typical transformer one sees in a textbook has two parameters N1 and N2. The relation between Vin and Vout is then Vout = (N1/N2 ) Vin. In other words, N1:N2 is the ratio. If N1 < N2, then it is a step down transformer.

However, most transformers one can buy have rating of Vin and Vout with specific numbers. For example, Vin = 12 V and Vout = 6 V. I do not understand how this works. If I input a 9-volt voltage to this transformer, what would happen? Does it have to take 12 V as its input?

Thank you.

 

12V:6V means that the turns ratio is 2:1.

Hence 9V in would give you 4.5V out.

 

But you can't generally put more voltage at the input then its rated voltage at the rated frequency or the transformer core can saturate with subsequent high input current.

 

N1 presumably states the primary winding turns and N2 the secondary winding turns.
Surely if N1 < N2 (or N2 > N1) then one has a step up transformer .....