DC Power Supply maximum current
There are a number of things that can happen.


The supply blows a protection fuse.
A designed in circuit breaker trips.
The supply let's out smoke and dies.
The supply output voltage is dragged down to some much lower output voltage and delivers less current correspondingly.
The overload makes the supply temperature rise to a point where a thermal switch cuts off either to input or output.
The supply detects the current overload and shuts down the output.