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Old 02-03-2010, 01:49 PM   #202 (permalink)
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Originally Posted by williamson View Post
But not one 60 hertz motor has any expectation of staying together at any higher speed. Or, for how long? I would think anyone going into AC drive should find a motor rated at at least 5000 rpm, to avoid the constant shifting, or, EXPECT to shift. Kindest regards to all, williamson
I found the following article about using induction motors as generators:
Induction generators: What can go wrong? | Electrical Apparatus | Find Articles at BNET
Don't induction generators need an overspeed capability, for mechanical integrity, beyond what's available in a standard motor? At least one engineer has made that claim. The answer, however, is no. Although the latest NEMA standards are somewhat ambiguous, MG 1 Part 30 allows "maximum safe operating speeds" (for typical standard motors 250 hp and below) ranging from 125% to 200% of synchronous RPM. For brief periods (two minutes) with the machine de-energized, as for a running generator that's electrically disconnected, even higher speeds are allowed by the standards. Special capability for generator operation neither exists nor appears necessary.
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