DRIVE CIRCUIT AND ELECTRIC MOTOR FOR SUBMERSIBLE PUMPS

摘要

An electric submersible pump contains an AC permanent magnet motor havingthree or more phases A, B, C and has a drive circuit for supplying varyingdrive signals to all the phases of the motor at the same time. Each drivesignal is constituted by a cyclically smoothly varying voltage applied to thecorresponding motor phase during driving of the motor. The circuit comprisesswitches (902, 903) for each motor phase, a control arrangement for turningthe switches (902, 903) on and off at a frequency greater than the frequencyof the cyclically smoothly varying voltages, and a filter (907, 908) forfiltering the output voltages of the switches (902, 903) to produce thecyclically smoothly varying voltages. Such a drive circuit drives all thephases of the motor continuously such that damaging transients will not ariseand without requiring the motor emf or drive signals to be sinusoidal.