110224-1953 est
EEC:
In an ideal transformer the primary current would be zero with no load on the secondaries. But we only have ideal transformers in our mind and on paper.
shamsdebout's comment is probably a reasonable value for a real world transformer.
The unloaded input current is non-linear and has a large inductive component. All the standby heat loss in the transformer translates to the no-load resistive component of the standby primary current.
At my website
http://beta-a2.com/EE-photos.html see photo P8 for a scope picture of the unloaded excitation current to a transformer with nominal input voltage. The peaking of the current results from the core starting into saturation.
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