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HVAC School - For Techs, By Techs

Aug 29, 2019

Eric Kaiser joins the podcast again, and this time, we are talking ECM motors. We discuss types, history, diagnosis, and failure prevention.

An ECM motor has a permanent magnet rotor, which means that the magnetism never deactivates. The variable frequency-driven motor is typically an induction motor, and the rotor only becomes magnetized by the stator's field. Eric describes ECM motors as three-phase AC motors, but we can control the AC pulses, resulting in oddly shaped sine waves. Those motors essentially convert the AC power to DC power and then to controlled AC power with the help of a microprocessor that measures back EMF.

ECM motors have been in the industry since the 1980s. General Electric designed them to put out a constant volume of air against a wide range of static pressures. As time has gone by, manufacturers have developed those motors to overcome a wider range of duct challenges. and to communicate with controls and display components. One of the most significant developments in ECM motor manufacturing was the constant torque motor, also known as the X13 motor. There are also constant speed and constant airflow ECM motors.

When diagnosing ECM motors, you will want to be aware of the signals. The 24v signals work similarly on constant speed and constant torque motors but differently on constant airflow motors. Sometimes, only the module has an issue, which can be separated from the motor and individually replaced quite easily.

Eric and Bryan also discuss:

  • Modified or pulsed sine waves
  • RPM as feedback
  • PSC vs. ECM motor efficiency
  • Temperature's effect on a motor's lifespan
  • Achieving rated static pressure
  • How moisture can impact motors
  • Overvoltage events and motor failure
  • Programmable speed taps
  • Informational resources on ECM motors

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