Patent ID: 6745083
Filing Date: 2004-06-01
Classification: G05B

Abstract:
A method for monitoring a speed of an electric machine, comprising the steps of:providing a communication link to connect two processors; configuring a first one of the processors to monitor the speed in accordance with a first checking mode; configuring a second one of the processors to monitor the speed in accordance with a second checking mode, wherein the first and second checking modes are different; and cross-comparing results derived by the first and second processors, wherein the first checking mode includes executing a conventional control algorithm, checking on the basis of an estimated or measured value of the speed whether a speed limit has been exceeded, and executing a response action, when the speed limit has been exceeded, and wherein the second checking mode includes determining from actual current values an actual output frequency of an associated converter, checking on the basis of the actual output frequency whether the speed limit has been exceeded, and executing a response action, when the speed limit has been exceeded.