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Method and apparatus for monitoring the rotating frequency of de-energized induction motors

  • US 5,714,862 A
  • Filed: 05/02/1996
  • Issued: 02/03/1998
  • Est. Priority Date: 05/02/1996
  • Status: Expired due to Fees
First Claim
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1. In an induction motor system including an induction motor having power input terminals and producing a residual voltage signal at said power input terminals after deenergization of the motor, a circuit for monitoring the rotational speed of the induction motor after deenergization thereof, said circuit comprising:

  • (a) sensor means for sensing the residual voltage signal at said power input terminals and for producing an output in accordance therewith, b converter means in electrical connection with said output of said sensor means, for converting said output of said sensor means into a voltage level proportional to the frequency of the residual voltage signal and thus to the speed of the induction motor, and c a variable frequency motor controller in electrical connection with said voltage level of said converter means, adapted to control said induction motor by regulating an output characteristic of said controller relative to the speed of the induction motor after deenergization.

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