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  1. #14
    Join Date
    Feb 2005
    Dothan, Al

    Thanks Shop hound

    Thank you, Shop

    good information !
    Have always been a K.I.S.S. type person. Am going to have to modify my own ideas and enter the world of variable speed systems.

    One more question - The link you sent me to indicated that an ECM motor was a DC motor, is this right?? Need to understand as speed control is different in DC than in AC motors.

  2. #15
    Join Date
    Nov 2003
    The ECM motor might be fed with d/c but actually works just like a 3 phase ac motor as far as speed control goes. They really should describe it as a pulse width modulated dc motor. The motor itself actually has 3 windings just like a 3 phase ac motor and if the 3 pwm outputs where compared on an osciloscope it would resemble 3 phase ac.

  3. #16
    Another good source on the web for information on this is

  4. #17
    Join Date
    Apr 2004
    golan is right, it is a dc motor with 18 poles and the stator is a 3 phase. At any given time 12 of the 18 poles are energized (2 of 3 phases). Its a brushless DC motor, very efficient.

    The module is the end bell where the rectifier, capacitors, output module, and software are stored. Each model furnace or air handler has a different software in the module as well as number of capacitors is determined by voltage and motor HP.

    AC supplies power, is rectified to a somewhat dirty DC voltage if you will, and some very large capacitors clean it up. The output uses the PWM to control the motor speed which is determined by the software and inputs from the control board in the furnace or air handler.

    ECM is Electronically Commutated Motor. Commutated is simply moving magnetic fields to turn the motor. Electronically, well you know that.

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