Exciting system selection for brushless synchronous machine

The paper deals with the special brushless synchronous electrical machine (SBSM) working with an extensive variable load. It´s exciting systems usually keep cosφ ≈ 1. Among them are unmanned deep-well oil pumps drives, wind renewable energy SBSM, etc. The SBSMs usually works in harsh climate conditions, where thyristor or IGBT exciting systems are not reliable (except diodes). Oil field drives are supposed to have fire/explosion-proof brushless motors. It is shown in this paper that replacement of induction motors (IMs) with the special brushless synchronous motors (SBSM) with stable cosφ ≈ 1 in the sucker-rod pumps (SRPs) will help to cut energy losses and diminish voltage pulsations in the oil field electric network. It also results in some reduction of oversize motor utilizations. The main proposal of this paper is to avoid any controlled electronic exciting system, but at the same time obtain the stabilizing cosφ ≈ 1 effect by application of the special small construction change in the motor.