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Electric motor load sensing system

  • US RE33,874 E
  • Filed: 10/10/1989
  • Issued: 04/07/1992
  • Est. Priority Date: 05/22/1986
  • Status: Expired due to Term
First Claim
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1. [.An underload.]. .Iadd.A .Iaddend.protection system adapted to be connected to an electric motor and first and second power supply lines, the lines being connectable to an AC power supply supplying a line voltage and line current, said system comprising line voltage sensing means adapted to be connected to said lines and to have a line voltage signal impressed therein, an amplitude adjustment circuit connected to said voltage sensing means and adjusting the duration of the line voltage signal in proportion to the value of the line voltage to produce an amplitude adjusted voltage signal, line current sensing means adapted to be connected to the second line and to have a line current signal impressed thereon, a phase adjustment circuit connected to the current sensing means and adjusting the phase of the current signal to produce a phase adjusted current signal, phase responsive means connected to said amplitude adjustment circuit and to said phase adjustment circuit and producing .[.an adjusted.]. .Iadd.a .Iaddend.power factor signal, and .[.disconnect.]. .Iadd.circuit .Iaddend.means connected to said phase responsive means and .[.adapted to disconnect the power lines when.]. .Iadd.responsive to .Iaddend.the power factor .[.is below a preset value.]. .Iadd.and therefore the load on said motor.Iaddend..

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