Historically, AC motors were used as the principal air driving force in HVAC applications running constantly at full power. The continuously increasing demand for a more energy efficient solution with a greater range of operation possibilities led to the development of the Electronically Commutated (EC) motor.
Since its development in the 1960s, EC technology has steadily grown market share and replaced AC technology in many air movement applications. Due to the substantial energy efficiency improvement in motor technology that EC offers, it is now seen by many OEM product designers as the new standard motor to employ.
Primary motivators for the move from AC to EC are minimum efficiency standards. Rising standards push towards more efficient technology approximately every three years and manufacturers must continue to improve to adhere to these regulations.
Electronically Commutated technology combines AC and DC voltages. In HVAC applications, this is fundamentally a fan with a brushless DC motor that amalgamates the best of both technologies. The motor uses DC voltage and permanent magnets within the motor windings, but with an AC supply. DC motors have an inherently low power consumption and much less motor slip when compared to their AC counterparts but if used in an AC application, the power needs converting AC to DC. This requires using a bulky, inefficient transformer. Whereas, the EC motor incorporates voltage transformation within the electronic section of the motor. The non-rotating part of the motor is extended to make room for an electronic PCB which includes power transformation AC to DC much the same process as within a motor drive or inverter, as well as the controls.
An EC motor is also extremely useful when supply voltages are not always standard, slightly higher or lower than normal voltages can be accepted by the motor electronics, the voltages then go through a rectifier which provides the correct supply to the motor, high or low voltage the motor nominal performance remains the same.
All the features of the external rotor motor are kept, including compact assembly, easy speed controllability, efficiency and airflow characteristics.
EC motors deliver very high efficiency even at low speeds due to the reduction in motor slippage they also have excellent control using analogue or digital control 0-10vDC, pulse width modulation or Modbus. They are simple to connect, individually preconfigured, compact in design and have a high power density. The implementation of additional functions (e.g. volumetric flow and pressure control) is also possible. Main benefits include:
With minimum efficiency regulations expected to rise every few years, manufacturers must continue to develop EC technology or, indeed, a new branch of motor technology to keep pace with regulations and market expectations. However, it should be remembered that cost is a key factor in the choices faced by procurers and will determine the success of any new technology.
Developments need to be cost-competitive as well as providing efficiency gains to build market share or replace old technology. Furthermore, the new demands of Industry 4.0 should not be overlooked and so a focus on synergising motor technology with automation and data exchange should be adopted.