No power? No problem

May 18, 2000
Technology from TECO-Westinghouse Motor Co.

Technology from TECO-Westinghouse Motor Co., Round Rock, Tex., allows motors to operate more consistently despite weak, intermittent, or unreliable power supplies.

TECO-Westinghouse has teamed with Precise Power Corp., the originator of what's called the Written-Pole motor concept. Motors using Written-Pole technology combine the efficiency and constant-speed characteristics of a synchronous motor with the high-starting torque of an induction motor.

Interestingly, motors with Written-Pole technology have a rotor surface covered with a continuous layer of magnetic material. Its stator windings are similar to those of conventional induction motors but also contains an additional concentrated winding that forms a writer-pole.

In Written-Pole motors, "permanent'' magnet poles are continuously and instantaneously written on a magnetic layer in the rotor by an exciter pole in the stator. The magnetic poles are written to a different spot on the rotor during each revolution when rotor speed changes. This keeps the pole pattern at a constant poles/sec speed.

Most Written-Pole motors feature an external rotor that spins around an internal stator, opposite that of conventional motors. This inverted structure creates a flywheel effect that allows the machine to ride through 99% of power-quality disturbances, according to company officials. At full load, Written-Pole motors can provide full power to driven equipment through power interruptions as long as 15 sec.

Another advantage is apparent at start-up. The rotor's construction with permanent magnets reduces starting current. In fact, written-pole motors need only one-third the amount of starting current as conventional induction motors.

In a conventional generator, the internal rotor must spin at a fixed speed such as 1,800 rpm to give a steady output frequency of 60 Hz. Two seconds after a power interruption, the conventional rotor's speed decreases to about 1,260 rpm. Since the positions of a conventional rotor's magnetic poles are permanent, when the rotor falls behind, the output frequency drops to 42 Hz -- enough to disrupt equipment. A Written-Pole generator's rotor speed also decreases after a power interruption but the generator's pole-writing coils can rewrite the north and south poles on the magnetizable layer of the rotor 60 times/sec. Essentially, the coils position the poles where they need to be to maintain a 60-Hz frequency, avoiding load disruption.

Continue Reading

Sponsored Recommendations

From concept to consumption: Optimizing success in food and beverage

April 9, 2024
Identifying opportunities and solutions for plant floor optimization has never been easier. Download our visual guide to quickly and efficiently pinpoint areas for operational...

A closer look at modern design considerations for food and beverage

April 9, 2024
With new and changing safety and hygiene regulations at top of mind, its easy to understand how other crucial aspects of machine design can get pushed aside. Our whitepaper explores...

Cybersecurity and the Medical Manufacturing Industry

April 9, 2024
Learn about medical manufacturing cybersecurity risks, costs, and threats as well as effective cybersecurity strategies and essential solutions.

Condition Monitoring for Energy and Utilities Assets

April 9, 2024
Condition monitoring is an essential element of asset management in the energy and utilities industry. The American oil and gas, water and wastewater, and electrical grid sectors...

Voice your opinion!

To join the conversation, and become an exclusive member of Machine Design, create an account today!


Most Read