An expansion valve is a flow-restricting device present in a refrigeration system that causes a pressure drop of the working fluid. The valve needle remains open during steady-state of operation. The size of the opening or the position of the needle is related to pressure and temperature of the evaporator. When set and controlled properly, an expansion valve will keep the evaporator active throughout its operation. There are two types of electric expansion valve technologies popular in the market place - pulse width modulated valves, and stepper motor driven valves.