It is possible to series connect the secondary windings in order to get a higher voltage. Take care to get phasing right though.
It is NOT possible to daisy chain transformers or even switch the primary and secondary windings in order to raise the voltage. (I tried that when i was 9... lots of smoke and lots of abuse from my father..)
The reason for this that the iron in the transformer coil can only withstand a certain flow density (normally 1,2T). So even if you increase the magnetomoric force (=current or ampereturns) the flow density will not go over 1,2T(saturating the core) thus collapsing the whole inductance model. This is best described by the transformer formula:
U=4,44BmaxANf
where
- U = RMS voltage in winding
- 4,44 = pi*sqrt(2)
- Bmax = maximum flow density in core, normally 1,2T for omnidirectional transformer steel, 1,8T for unidirectional transformer steel.
- N = Nuber of turns in winding
- f = frequency
This also explains why you can use a smaller tranformer (less iron and less copper) at higher frequencies. Thats why a switched power supply is much smaller than one with a traditional transformer. switching frequency is normally 40kHz or so
