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Motor control system for a plastic forming machine

  • US 4,904,913 A
  • Filed: 07/18/1988
  • Issued: 02/27/1990
  • Est. Priority Date: 07/18/1988
  • Status: Expired due to Term
First Claim
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1. A motor control system for a motor which powers one or more hydraulic pumps for supplying pressurized hydraulic fluid to a plastic forming machine during operation functions of the machine, said machine having a plurality of electrical signal points, each signal point corresponding to an individual operation function of the machine such that at least one electrical signal is applied to each signal point when the machine is in an operation function, the machine having operating time intervals during which a least one operation function is present, the control system comprising,input leads individually connected to each of said signal points,an interface circuit includingan output lead,a voltage source, andlogic circuit means connected to said voltage source and to said input leads for generating on said output lead a logic control signal comprising a time stream of voltage level steps corresponding in time to said operating time intervals of said plastic forming machine, wherein the voltage level of each step is representative of the power needed by said motor to provide approximately the least amount of power necessary to power said hydraulic pump for each of said operating time intervals, andphase inverter means having a line frequency alternating current power source applied to it and responsive to said logic control signal for applying output alternating current power of variable frequency to said motor which powers the one or more hydraulic pumps of said plastic forming machine, said frequency of said output power being approximately directly proportional, during each of said operating intervals of said plastic forming machine, to the voltage level of said logic control signal.

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