Engineers have many options for motor selections, but most fans can be categorized into four types of motors:
- Alternating Current (AC)
- Direct Current (DC)
- Electronically Commutated (EC)
- Permanent Magnet Electronically Commutated (PMEC)
Alternating current (AC) and direct current (DC) have been the most common motors throughout the years. Recently, a newer, more efficient type has emerged called an EC motor. Facilities have been seeing massive benefits from using this EC technology. Now, there is even another development on EC motors to create the PMEC motor. We’ve seen many replacements from AC and DC motors to the new EC motors.
Here is a comparison of each motor type.
What are AC Motors?
AC motors run on alternating current, using a series of coils energised by the incoming supply voltage. They are the long-standing workhorse of HVAC air movement: robust, inexpensive and well understood, but they need external speed control such as a VFD to run at anything other than full output.
AC motors require higher input voltages to create a magnetic field. As a result, AC motors are less efficient than DC motors
Advantages of AC Motors
- Long-established technology
- Replaceable and serviceable components
- Abundant supply
Disadvantages of AC Motors
- Low efficiency at part load
- Requires maintenance
- Requires VFD (Variable Frequency Drive)
- Noisey
- Average power and torque density
What are DC Motors?
DC motors run on direct current, where the electrons flow in a single direction rather than alternating. That steady supply makes speed control simple and efficient, but it requires a DC power source, which is why straight DC motors are uncommon in building HVAC without conversion electronics.
DC motors are highly efficient but still face specific losses. They lose efficiency from initial resistance in winding and friction.
Advantages of DC motors
- More energy efficient than AC motors
- Versatility with power
Disadvantages of DC motors
- Require maintenance
- Limited lifespan
What are EC Motors?
EC stands for electronically commutated. An EC motor is a DC motor with the commutation and drive electronics built into the housing, so it accepts an AC supply and converts internally. That gives DC efficiency and integrated speed control without an external VFD, which is why EC dominates direct-drive fan design.
Advantages of EC motors
- Highly efficient at part load
- No maintenance required
- No VFD required
- Require less space lengthwise
- Excellent power and torque density
Disadvantages of EC motors
- Poor availability currently
- Components can not be individually replaced
What are PMEC Motors?
PMEC stands for permanent magnet electronically commutated. These motors combine permanent magnet and synchronous reluctance technologies, which raises efficiency further than standard EC at partial load. They are the current high-efficiency option where operating hours are long and energy cost dominates the lifecycle figure.
Advantages of PMEC motors
- Excellent full range efficiency
- Smaller than traditional AC motors
- Replaceable and serviceable components
- Readily available Synchronous Reluctance technology, no rare earth materials required
Disadvantages of PMEC motors
- Not as compact as conventional EC motors
Recap of Motor Types
While AC motors, and to some extent EC motors, have been the standard for commercial HVAC equipment for many years, PMEC motors have proven to be a solid choice for the future of AHUs. With better efficiency, less maintenance, and compact design, PMEC motors are an excellent choice.
Looking to upgrade your fan systems with PMEC motors? Contact Mainstream today to get started!