Improved power quality with "written-pole" motor-generators and "written-pole" motors

Abstract

Written-pole AC motors and generators can be controlled to continuously vary the magnetic pattern of permanent magnet rotor field poles while the machines operate. This unique feature allows machines to be built that can protect a wide variety of critical loads from poor power quality. Applied in a motor-generator set, pole writing allows the generator to produce high quality sine wave constant frequency output at variable speed. The motor uses written poles to efficiently operate its own high inertia energy rotor as a flywheel energy storage device. The M-G set improves power quality by providing continuous on-line isolation between the electrical distribution system and load and by ride-through of blackouts of 15 seconds or more while supplying full load at exact frequency and regulated voltage. Inherent rotating energy is used, thus eliminating the need for batteries. The power quality is also improved for the electrical distribution system because the generator can serve severe harmonic and pulse loads and prevents harmonic feedback. The motor is a clean sine wave, unity power factor load and has added advantages of high efficiency and very low inrush current during across-the-line starts. Conventional loads such as pumps and fans can be driven by written-pole motors. These will have advantages of load ride-through during momentary power interruptions and instant restart ability. Additionally, low starting current will significantly reduce voltage sags on the distribution line, improving power quality for neighboring loads. The paper describes the technology and its benefits for power quality.