Written-Pole^® Converter Supplies Quality Three-Phase Power to Remote Load;  Meets Stringent Flicker Specification

ABSTRACT:  A Written-Pole® PowerRide™ motor drives a 3-phase generator.  The M-G set provides 3-phase power to drive any appropriate load, such as 3-phase electronics, industrial loads, or 3-phase motors.  The generator portion is significantly over-sized to provide large starting current for conventional motors up to 50 HP and provides clean, well-balanced voltage sinewave output.  The Written-Pole® motor improves power quality on the distribution line and supplies ride-through during voltage sags and blackouts caused by recloser operations.  A “velvet start” design is also described in which the starting current of the motor is actually less than full load operation current.  This results in very low flicker during start.  A case study is presented showing avoided cost of $200,000 for 3-phase extension, as well as avoiding 3-phase availability charge of $15,000 per year.

INTRODUCTION: Written-Pole® motors change the magnetic poles on the rotor while the motor operates.  They start with low starting current and then run synchronously.  The first Written-Pole® motors were built “inside-out,” with the rotor outside of the stator.  This was done to provide high inertia to ride through power interruptions.  Low starting current does not overheat the motor windings, and high inertia loads start easily.   These motors are called “external rotor” or PowerRide™ design.