Accuracy (Electric Motors)

10.4.4
In general, optical encoders have an advantage in this area, followed closely by Inductosyns. Angle measurement systems can be as good as 0.18″ (0.00005°). Induc-tosyns can reach 0.32″ for minimum resolution. High-resolution self-contained encoders have a minimum resolution of about 12″ or //» cycle, which for a 2000-count encoder can be as low as 32″. Modular incremental rotary encoders usually have an accuracy rating of 2′ or better.
Although specially fabricated resolvers can be obtained which are accurate to ± 2′, in general, resolvers have accuracy ratings of ± 2 to ± 20′.
Hall switches can achieve a resolution of about 5°, and are typically very difficult to align. This can be a real problem in a brushless motor commutation application. In these applications, the switching point should be optimized in order to ensure minimum torque ripple and to maximize motor performance. For these applications, resolver and optical encoder commutation can be good to ± 10′ with some careful planning, and

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