Transformaer Impedence matching.

[lord loh.]

Is it necessary to calculate the impedence matching in a simple step down transformer considering the line frequency ?

Will a transformer designed for 60 Hz fall out on efficiency at 50 Hz ?

How is the current rating of the transformer detirmined ? by the thickness of the wire or the number of turns ?

To make a step down from 220 to 110 one could either do it by having 2 turning on the primary and 1 on the secondary or 2000 on the primary and 1000 on the secondary....What is the difference ? efficiency ?


Please Help!!!

 

[fsahmed]

1. Impedance matching is how the transformer supply side (primary) sees the load (connected on the secondary), its calculation is important only when u intend to follow max. power transfer theorem.

2. Frequency change may effect the impedance of the transformer resulting in reactive losses, other than that, no significant decrease in efficiency occirs.

3. The current rating is determined by both the thickness & the number of turns.

4. Remember that current is simply the flow of free electrons. Giving only 2 turns on primary & 1 on secondary would result in

a. Very low power rating (current handling capability would be very low)

b. Very low impedance which could result in shorting the input power supply if it is working on low frequency. Corollary to it, the greater the frequency, the smaller the transformer gets giving the same power ratings.

A two turn primary & one turn secondary transformer, if made & daringly connected to the mains power will, until it blows up or some circuit breaker trips, will not have as much power (VA) rating as a 2000/1000 one.

 

[Zarkabul]

In addition to fsahmed's writing:

E = 4,44 x f x (phi)max x N

where E is the induced voltage on the turns, f is the frequency, (phi)max is the max. magnetic flux and N is the number of turns. This formula can be acceptable for transformers.

As you see if you want to reach higher voltages or power levels you need much more number of turns than 1 (under fixed (phi)max and f). You need thicker wire as the current increases, the wire that can endures the current flowing over the turns. Meanwhile, you can increase the frequency to get higher voltage levels, thus the number of turns can be decreased and also the size of the transformer, as used in power supplies or audio transformers.

 

[2ny]

Is it necessary to calculate the impedence matching in a simple step down transformer considering the line frequency ?

Will a transformer designed for 60 Hz fall out on efficiency at 50 Hz ?

How is the current rating of the transformer detirmined ? by the thickness of the wire or the number of turns ?

To make a step down from 220 to 110 one could either do it by having 2 turning on the primary and 1 on the secondary or 2000 on the primary and 1000 on the secondary....What is the difference ? efficiency ?

for power transformers, not nescessary, but for audio it is, maximum power transfer occurs when load impedance equals source impedance!

there will be little impact on efficiency for a 60hz traffo running 50hz, well most of the time!

regarding transforming 220 to 110 you have the general idea, however with regards to the number of turns you specified, the magnetic part (core) must also be specified. as it is, 2000 turns is true for a unique core area, 0.6 sq. inch is minimum core area you can use for this number of turns.