I have heard of profile power having "installation" power included for convenience when drawing up the power / IAS graph. "Installation" power stays more or less constant regardless of speed. In fact if it includes the tail rotor power, it may decrease slightly with increased IAS due to the translational lift effect on the tail rotor.
Profile power typically increases gently until blade stall effects occur (on the retreating side) when the curve increase in steepness and then again very sharply as compressibility also affects the advancing blade side.
p.s. Don't forget parasite power!
[This message has been edited by ShyTorque (edited 19 March 2001).]