Abstract: A method and apparatus for controlling an artificial lift system is described and claimed. Preferably, the control system includes at least one sensor for detecting at least one mechanical attribute during pumping operations, and a controller for receiving the electrical signal as an input, and analyzing it to determine if a pumped-off condition is occurring. Additionally, the controller member provides command signals to control the prime mover and to suspend operation of the prime mover if it is determined that a pumped-off condition is occurring. The controller maintains the suspension of the prime mover for an idle interval having a duration which is calculated by the controller from (1) at least one preceding pumping interval, and (2) a predefined pump cycle duration. Preferably, the controller operates to maintain a substantially constant and predetermined pumping cycle duration by continuously adjusting the idle interval duration.

Abstract: A microwave waveguide is presented which includes a gas tight seal which provides pressure isolation between two portions of the waveguide. In accordance with an important feature of this invention, an upper flange includes a threaded axial opening for receiving and retaining a threadably mated dielectric filling material. If the thread pitch is small relative to the signal wavelength, the threaded section has essentially the same electrical characteristics as a smooth waveguide. The resulting structure provides an economical and practical method of retaining a solid dielectric filling material in a waveguide against high pressure without changing the effective diameter of the waveguide. In accordance with another feature of this invention, a novel high pressure seal is provided between the upper and lower flanges in the area surrounding the threaded axial opening.