Improved power quality with "Written-Pole" motor-generators and motors

Written-Pole motor-generators and motors improve power quality because the magnetic pattern of rotor field poles can be changed while the machines operate. Applied in a motor-generator set, pole writing allows the generator to produce high quality constant frequency output at variable speed. The motor efficiently operates its own high inertial energy rotor as a flywheel energy storage device. The M-G set provides continuous on-line isolation between the electrical distribution system and load. It also rides through blackouts of 15 seconds or more while supplying full load at exact frequency and regulated voltage. Rotating flywheel energy is used, thereby eliminating the need for batteries for uninterruptible power. Power quality is also improved for the electrical distribution system because the generator prevents harmonic feedback. The motor is a unity power factor load with negligible harmonics and has added advantages of high efficiency and very low inrush current during across-the-line starts. Mechanical loads such as pumps and fans can be driven by Written-Pole motors. These can also have advantages of load ride-through during momentary power interruptions and can instantly restart. Additionally, low starting current significantly reduces voltage sags on the distribution system, improving power quality. Such motors are being developed in single-phase with the Electric Power Research Institute (EPRI) and member utilities. The paper describes the benefits for power quality as a result of Written-Pole machines