Motor Designs To Survive Hostile Environments

Article by Richard L. Halstead, President, Empire Magnetics, Inc.

A new generation of step motors is allowing motion control applications to prosper where they were previously impossible or, at best, very difficult. The reason?

Previous step motor designs were developed for the relatively “benign” conditions in a factory. New step motor designs – specially developed for motor-hostile environments – can reliably withstand the effects of radiation, underwater operation, vacuum operation, and extremely high and low temperatures, among other conditions. Accordingly, these motors are the key to a wide range of new motion control opportunities.

Vacuum Motors

The problems inherent in operating a motor in a vacuum – outgassing, contamination and temperature – are well known to design engineers. Solutions are less well known. Common requirements for vacuum operation include the ability to accurately move or position samples, products, mirrors and sensors. continued…

Waterproof Step Motors

Because of the preponderance of water and solvents, motion control components are often exposed to the risk of corrosion and failure. Waterproof motors are a key part of the solution to water-induced motor failure problems. continued…

Radiation-Hardened Step Motors

Conventional step and microstepping motors are susceptible to high-energy gamma radiation particles that will attack non-metallic materials. As a result, lubricants, varnish, lamination bonding, and cable insulation will all deteriorate over time and finally crumble. continued…

Extended Temperature Step Motors

Extended temperature step motor applications offer some particularly extreme operating conditions. As a satellite rotates in orbit, for instance, its motors experience incredible temperature swings as they move from the blazing sun (+200∞ C) to freezing shadow (-200∞ C) in a matter of seconds. continued…

Low Temperature Motors/Cryogenic Motors

Contraction of metallic parts and hardening of non-metallic parts are the two primary factors that can render a step motor non-functional in low temperatures. In the instance of contraction, if motor components with critical dimensions contract at different rates, a locked-up motor may result. The resultant stress can crack metal parts made brittle by super-cooling.
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High Temperature Motors

At high temperatures, the principal failure mode is winding insulation failure and the resulting short circuit that occurs. To combat this problem, high temperature magnet wire rated to 180∞ C is commonly specified. continued…
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