Patent ID: 9054615
Filing Date: 2015-06-09
Classification: H02P

Abstract:
1. A method of controlling an electric power supply to a synchronous permanent magnet motor within a wellbore having a plurality of windings so as to accelerate the motor through a range of speed from rest, comprising: supplying each of the plurality of windings of the synchronous permanent magnet motor within the wellbore with a root mean square supply voltage V applied at a supply frequency f via a respective conductor according to an initial constant voltage V0, a constant ratio of voltage over frequency vf_Ratio, and the supply frequency f; and determining, prior to supplying each of the plurality of windings with the root mean square supply voltage V applied at the supply frequency f, the initial constant voltage V0 from one or more characteristics of the synchronous permanent magnet motor and one or more characteristics of the respective conductor that supplies the root mean square supply voltage V to the synchronous permanent magnet motor, wherein the initial constant voltage V0 is a predetermined value that is sufficient to supply a current to generate a required torque to turn the motor from a stationary position, wherein the constant ratio of voltage over frequency vf_Ratio is sufficient to provide excess torque for a start-up period and an operation period that overcomes a transient load, and wherein the power supply is controlled independently of a rotor position signal.