That is the compiler optimizing for you 
If you never call ReadSerial (bad name because you do a lot more then just reading serial ;)) angel1 (again, bad name, where is angle2? Or why isn't it a nice array) is never changing. The compiler notices that and tsays "fine, I will calculate ph1, ph2 and ph3 now". So the 480us is right. Doing float math is slow, doing sin calculations is slow. If you want fast, drop the float (float is NOT just a decimal point) and switch to a look up table. And while you're at it, drop String and use a string.