Is bigger really better?
Should you use the largest transformer for every application?
As discussed in the article Transformer Current Ratings maximum current ratings and Voltage are linked and there are health and safety regulations that cap the maximum open circuit Voltage at 24V.
But should you use a 24V transformer for every application? The short answer is no.
The long answer is transformers capable of producing higher currents and Voltages are physically larger and cost a lot more. They also need more power to run them and some organisations do not have an electrical supply capable of running them.
There is also another consideration...
Control at the bottom end
Another crucial fact to consider is how transformers operate at the lower end when using low currents - Transformers are harder to accurately control at lower current values.
This can be negated to some extent by manufacturing transformers with ‘tappings’ where the circuitry inside the MPI equipment only uses a section of the transformer and in effect pretends that section is a smaller transformer.
As a rule of thumb Johnson & Allen guarantee control down to 10% of maximum output but often our units can control at lower current values - However we advise customers discuss this with our Technical Sales team to confirm.