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Electrical power tool having a motor control circuit for providing control over the torque output of the power tool

DC
  • US 6,424,799 B1
  • Filed: 04/03/1997
  • Issued: 07/23/2002
  • Est. Priority Date: 07/06/1993
  • Status: Expired due to Term
First Claim
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1. A power tool having an electric motor for driving an output spindle having a tool holder operatively coupled thereto, an operator actuable switch for controlling the amount of power applied to the motor, and a control circuit for modulating the power supplied to the motor in accordance with the position of said switch by varying the duty cycle of a constant frequency, pulse width modulated (PWM) direct current (d.c.) control signal generated by the control circuit to thereby control the speed of the motor;

  • the improvement wherein the frequency of the PWM d.c. control signal generated by said control circuit is less than 50 Hz.

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