3. Rolling mill control concepts
AC motors, both synchronous and asynchronous, supplied at variable frequency are perfectly controllable in terms of speed, as were DC motors supplied by thyristor bridges. The accuracy of speed control depends on the control structure and, of course, the precision with which the speed is measured (number of pulse generator points).
Notes on speed capture
1 – In the past, we used tachymetric dynamos, and the problem of accuracy was mainly due to temperature drift. With modern controllers, we measure speed by counting with a GI (pulse generator), which means that dynamics and precision are linked. If a GI has a limited number of tops per revolution, low-speed operation is tricky, as the count refresh time is too long: you can therefore have good precision, but with very low dynamics... In practice, GIs...
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Rolling mill control concepts
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