How to measure power in watts in a power supply with current limiting?

[skillz21]

Have a look at this situation. I have a variable power supply connected to an AC-DC power supply which is rated for 20V 3A, or 60 watts. Now on my variable power supply, I set the voltage to 6 volts and current limit to 10 amps, and I put on a load that draws this amount of power. Now at this point, the current limiting would kick in, which drops the voltage down to somewhere near 100ma. In this situation, how much power would the variable supply be drawing from the main one? Would it still be 60 watts? (give or take a bit for power loss)

[Zero999]

You haven't provided enough information to answer the question. Is it a switched mode or linear power supply?

You also seem to have confused Volts with Amps.

[skillz21]

The main PSU is a laptop power brick, and the board I'm asking about is a switching power supply (a buck-boost DC to DC converter).

[ArthurDent]

You have 60 watts input times the conversion efficiency so you won't get 60 watts out. More realistic you could get 6 VDC at 9 A max, not 10.

[malagas_on_fire]

Plus the losses in heat, depending on the load applied ., cable length, section, when power delivering is max out.