18:54 Oct 18, 2011 

The real problem is how much energy can the winding support as a short term "pulse". A short term pulse of energy is an adiabatic process (no heat escapes out). The amount of energy is determined by the formula I**2 x R x t where I is the current, R is the resistance and t is time. Given that R is constant for a particular design (is determined by the manufacturer), the variables known to the user are I and t - so the user must make sure that - in this case the secondary winding - does not experience a value of I**2 x t greater that 10. The secondary nominal current is 5A - so, for example, for a 5A current, t must be no more than 400 milliseconds (5 x 5 x 0,4 = 10).
The complete theory is that the energy is actually the integral over time (dt) of I** x R - but that is beyond the scope of our discussion.
Hasta la Vista