Supposing we have a transformer and we want to find out what is the maximum DC current we can get regulated.

My (elementary) theory says this:

The power of the transformer's secondary will be expended on the bridge, regulator pass transistors and on the actual load. The DC current available will be the VA of the secondary divided by the peak rectified voltage (this voltage will be then divided on the regulator and the load).

So for a 150VA/25V/6A transformer we can get a maximum DC current of 150 / (25*sqrt(2)-2) = 4.5 A DC according to the theory above.

My simulator is less optimistic depending on the size of the filter capacitor : I get something like 1.8A to 2.2 A out of the 6A RMS of the secondary.

My theory has not accounted for the filter capacitor which influences the results negatively - although the bigger it is the smoother the output.

The above suggests that with a secondary of 25V/6A I am looking at about 1.8A-2.2A at most out of a regulated supply with a filter cap of 4.7mF to 30mF.

Have I done this right? It sounds so wrong to me.