Importance

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Abstract

An arrangement for sensing the operating condition of an alternating current machine employs a Hall switch on the stator which is subjected to the alternating magnetic field established during operation. The Hall switch has a magnetic field strength threshhold below which it will not be actuated. During normal operation of the machine, the alternating field strength will cyclically exceed the switch threshhold, thereby generating a series of pulses at the frequency of alternation of the field. Should the field strength decrease as a result of overload of the machine, a decrease in line voltage, or the like, to a level below the threshhold level of the switch, the pulse output of the switch will cease. Circuitry responsive to the absence of periodic pulses actuates an indicator circuit to warn of the faulty operation.

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First Claim