Variable Speed Control For Filtration

In 1985 when Pure Air Systems was formed, the air filtration industry was using standard induction ( copper wound ) AC motors to run the fans that moved the air across the various types of filter media. Most often these fan powered units used HEPA filters as their primary filtration media.  Since HEPA filters have a fair amount of resistance due to their very dense media design,  motors in the range of 1/3 HP to 3/4 HP and larger were used for these applications. For the most part, these motors were all single speed, 120 volt, 60Hz  AC motors. Using any type of speed reduction controller with induction motors was difficult as the reduction in voltage to reduce speed also increased the heat load on the motor and created a hum or whine sound when dialing down the speed. As a result, most of the systems ran at one speed and one voltage.

In the late 90’s General Electric introduced a variable speed motor referred to as an “electrically commutated motor,” or ECM for short. This motor operates on using magnets rather than copper winding’s and can run forward or backward at any speed from 1% to 100% in 1% increments when controlled with a digital controller. Further more, it was designed to operate at 120/240 volt, 50/60Hz so it could be  used anywhere in the world. This new motor technology provided for variable speed control for filtration systems.

When using the standard induction motors the fan ran at one speed, which was high. This made a fair amount of noise and made it difficult to use it in areas that were occupied or where individuals were sleeping, reading or watching TV. The addition of the ECM motors allowed for use of even larger HEPA based air filtration systems to be used anywhere as the speed of the blower can be reduced so that the sound levels from the fan noise are low enough not to disturb people where the system is being used. Even at low speeds, the filtration efficiency’s are very good so moving air slowly over a long period of time is as effective as moving it at high speeds for short periods of time.

Pure Air Systems has over 6 models of HEPA systems designed to provide filtered air in any environment with a high degree of control. These units can be attached to existing ducted  HVAC systems or as stand-alone units. For more information on the complete line of  HEPA and Carbon based air filtration systems please go to our website at: or contact us on our toll-free number: 800-869-8025.

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