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Motor assembly

  • US 5,577,152 A
  • Filed: 04/12/1995
  • Issued: 11/19/1996
  • Est. Priority Date: 04/12/1995
  • Status: Expired due to Fees
First Claim
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1. A motor assembly comprising a dc motor and a driving unit for driving said dc motor at different speeds, said motor including a stator and a rotor, said stator including a housing and a three-phase coil unit installed in said housing and provided with three windings, said rotor extending through said housing of said stator, wherein said driving unit includes:

  • a power supplying circuit for generating a dc output;

    a first power transistor unit including three first power transistors, each of said first power transistors being activable to connect electrically a respective one of said windings of said coil unit and said power supplying circuit;

    a driving circuit connected electrically to said power transistors of said first power transistor unit for activating said first power transistor unit when said power supplying circuit is activated;

    a sensor circuit for sensing rotating speed of said rotor and for generating three speed pulses which represent said rotating speed of said rotor and which are out of phase;

    a frequency-to-voltage converter connected electrically to said sensor circuit for generating an analog voltage signal corresponding to said rotating speed of said rotor;

    a speed setting unit activable to generate a reference voltage signal equal to a desired motor speed;

    a comparing unit connected electrically to said speed setting unit and said frequency-to-voltage converter for comparing said reference voltage signal with said analog voltage signal and for generating an analog error voltage signal having a magnitude corresponding to a difference between said analog voltage signal and said reference voltage signal;

    a pulse width modulating circuit connected electrically to said comparing unit for generating a variable-width modulated pulse signal with said analog error voltage signal as a modulating signal; and

    a second power transistor unit including three second power transistors, each of said second power transistors corresponding to one of said first power transistors and being activable to connect electrically said power supplying circuit and a respective one of said windings of said coil unit;

    said driving circuit receiving said three speed pulses from said sensor circuit and processing said speed pulses so as to activate intermittently said first power transistors such that two of said first power transistors are activated and one of said first power transistors is deactivated at any time;

    said driving circuit being further connected electrically to said pulse width modulating circuit and said second power transistors for activating one of said second power transistors corresponding to deactivated one of said first power transistors upon receiving said modulated pulse signal from said pulse width modulating circuit.

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