Need understanding on amperage

Dhl93449, your math looks right but your conclusion doesn't. At the end of 10mS the supply voltage is only 24V so the current would be 24 amps- only 576 watts. The fuse would go a little longer and the 3600 watt figure would go much shorter or am I missing something?

I think the change is voltage (dV) is 24V. So starting from 80V in DHl's equation means that the ending voltage after 10ms is 56V which is still 3136 Watts, right?

Atmasphere/Tonywise

Yes, the remaining voltage would be 56 volts, and the average power delivered would be between 3600 and 3136 Wts. And it may be somewhat less because we are not accounting for the voltage drop across the output stage transistors (it won't be zero, and will be dependant whether the transistors are being driven into saturation or not).

Guys, it was just a ballpark analysis. It also did not include the re-charge of the capacitor by the transformer or that perhaps both the V+ and V- capacitors might be discharged partially.

My point being is that the delivery of 60 amps to the load will be limited by the fuse characterisitcs primarily. Whether it is 10 milliseconds or 15 milliseconds is not that important.

BTW, I would hope that the fuse was sized to prevent the bipolar output transistors from going into secondary breakdown. If this happens, the power transistors fail and the entire output stage is toast before the fuse can protect them.

agree, Dhl93449 calculations showed the delta-V (or droop) across the power supply cap to be 24V meaning that the final voltage after 10mS would be 80V-24V=56V but at this point in time the fuse would have blown (per the Littlefuse data sheet) as the current draw from the wall would have peaked at 8A in a valliant effort to re-charge the drooping power supply caps. Thus, the output protection ckt should have kicked in ASAP to cut off the output signal from reaching the speaker binding posts & there should be pin-drop silence from the speakers! ;-) And, as Dhl93449 noted, the output stage is hopefully intact & there is no smoke curling out of the amp......

Right! Now this is just my feeling about the matter, but I don't think the 60 amp rating is realistic if it means that the amplifier could be damaged or the like in the process. At that point we are clearly operating outside of the linear region of the amp- and such an amp is intended for music not square waves.

Bombaywalla, its not a given that the caps would be charging if the window is 10mS. A lot would have to do with where the AC waveform was at the time of the 'event' :)

BTW thanks to all that have contributed here.