Sorry to throw that one at you - it sounds like an Oxy-Moron, doesn't it??
Dspark, thank you for posting the related message!!
The term "Rectifier Transformer" just means that it is intended to be used to feed an AC to DC converter - and the first thing that the AC sees in that converter is a Rectifier [first really active component that is - really it will see fuses or breakers first
After the currents leave the Rectifier[s] - which is [are] just an array of Diodes, it goes into a "Ripple Filter", then possibly a Voltage Regulator. After all that baloney, the output is now a somewhat stable DC - free to use as needed.
Funny thing here is this DC will be used on a typical UPS [Uninterruptable Power Supply], so after the AC has been converted into a nice clean DC, it gets inverted back into AC.
Current technology wise, we haven't yet found any other method for frequency inversion than this. If the output required either a lower Hz, or higher Hz than is present, the existing AC will be converted to DC, then the DC is turned into AC through a network of power transistors, which resembles the way an audio amplifier is connected [not very much difference between the two - they both do the same job!!].
Same goes for UPS devices, except there's no change in Hz between existing and output frequency.