How do i keep a 3 way light bulb on 150 watt with a conventional socket (such as a pan light)?

Are you using a 3 way bulb with 50W, 100W and 150W settings? In order to get teh full 150W from the bulb there are 2 contacts at the base of the bulb that need power. Inside the bulb there are 2 fillaments. One for 50W, and one for 100W. Both light up to give 150W of lighting. If your conventinal socket isn't bridging both contacts then try soldering a wire across them to get the full 150W.