Patent ID: 6739840
Filing Date: 2004-05-25
Classification: F04D,Y02B

Abstract:
A method of operating a variable speed pump in a vacuum processing environment comprising a vacuum chamber in fluid communication with the variable speed pump, and wherein the variable speed pump is in electrical communication with a power source, the method comprising:actuating the variable speed pump; sensing pressure in the vacuum chamber; increasing the speed of the variable speed pump to a first speed in order to decrease relative pressure in the vacuum chamber; operating the variable speed puma at the first speed for a period of time; maintaining a process pressure in the vacuum chamber; sensing one or more operating characteristics of the variable speed pump indicative of power consumption by the pump, wherein one of the one or more operating characteristics comprises gas load on the pump; and sensing a decrease in gas load on the pump; in response to determining a decrease of the gas load on the pump, sensing a stabilization of the as load on the pump over a selected period of time; and in response to determining a stabilization of the gas load on the pump, decreasing the speed of the variable speed pump to a second lower speed while still maintaining a process pressure in the vacuum chamber.