What Is a Fan Motor?

Fan Motor

What Is a Fan Motor?

A fan motor is a motor that drives the blades to move air through the duct system. Correct motor sizing is very important for a successful ventilation system.

Most fans have four wires: power, ground, a tach output and a PWM drive signal. PWM drives eliminate the need for pulse stretching and commutation noise, which reduces overall power consumption and electrical noise.


While fan blades may not be the first thing a homeowner thinks about when shopping for a new or replacement ceiling fan, they have a huge impact on both aesthetics and performance. In fact, certain types of blades are specifically designed to withstand outdoor environments while others are crafted to lower energy costs indoors.

When it comes to deciding what the right blade is for a home, the number of blades and size are important factors, but so is blade pitch. Fan Motor This is because the angle of a blade changes how much air it moves by changing the pressure exerted on a given surface.

A typical residential fan has a four-inch wide blade that spins on a rotor shaft and is powered by an electric motor. Generally, the higher the rotational speed of the fan, the more air it can move. The rotor is attached to the fan blades by hubs that connect to shaft bearings.

Some fans are powered by a pull chain, while others have handheld remotes or wall-mounted controls. The pull chain on a fan is an easy way to control the fan and its light, while remotes allow for a more customizable experience. It’s also possible to have a fan with no motor at all, and this is often the case for commercial or industrial fans.


When the fan bearings are damaged or worn out they will cause excessive friction that will elevate the temperature and thereby consume more energy. This is why regular inspection and monitoring of the fan bearings is important so that damage can be detected before it becomes serious enough to require replacement. If the bearings are making rattling noise or sound like they are grinding against each other, this is a clear sign that the bearings are going bad and that it is time to replace them.

Bearings come in a variety of styles and materials. In most fan applications a standard all steel sleeve type will work just fine. If the application has a heavy thrust load or concerns about misalignment, roller bearings are a better option as they can support high loads at very high speeds. If the bearing will operate in an environment that is subject to electrical erosion from variable-air-volume ventilation systems, or fire safe designs, then an anti-electrical corrosion type of bearing is a good choice.

For the most quiet and longest operating life, consider fluid dynamic bearing variations that go by a number of brand names (vapo, noctua, etc). These are a type of rolling element bearing that pumps or sucks lubricant around the sleeve to minimize the amount of friction between the shaft and the sleeve, resulting in a longer bearing lifespan than traditional sleeve type bearings.


A capacitor stores a fixed quantity of electric charge. It aids in the transfer of energy in electric gadgets and appliances like ceiling fans. Capacitors are small cylindrical shaped containers that look like large batteries with cables connected to them. There are two types of capacitors in a motor – the start capacitor and the run capacitor. The start Fan Motor capacitor helps the fan to get started while the run capacitor provides power to keep the motor running. If the motor is energized but fails to make any noise or slows down significantly after it starts then a bad capacitor is most likely the cause. To test the capacitor, you will need a high-quality electrical meter. Connect the leads of the meter to the terminals C and FAN (or C and Herm for compressor capacitors). A meter that reads in microfarads (abbreviated as uf) will confirm if the capacitor is good or not.

Without the capacitor, the current flowing through the start and auxiliary windings would cancel out each other after a half cycle of AC sine wave leading to zero rotating magnetic flux. The capacitor is responsible for creating a net rotating magnetic field that makes the rotor of the fan spin and generate starting torque.

Capacitors contain a significant amount of electrical energy and can be hazardous to handle. It’s important to follow safety guidelines when testing or replacing a capacitor. For example, it’s vital to discharge the capacitor before you work on it or you could be shocked.

Motor Case

When powered, current flows through the coils in the rotor, which acts as electromagnets, creating magnetic fields that act against the permanent magnets of the stator. This forces the rotor to rotate, which in turn spins the blades and creates air flow.

Once the rotor is spinning, the RUN capacitor (connected to both START and RUN windings) helps correct power factor issues. This can lead to better efficiency.

Adding more capacitance shifts the phases in the two windings further apart, which increases current and torque. This can also make the motor more sensitive to changes in the rotor speed.

The current passing through the rotor coils can also be controlled using an inverter, which makes it possible to control multiple fans through a single PCB. This can improve performance and reduce the number of motors required to run a larger fan.

AeroTech offers case adapters for most of their propellants in sizes ranging from 29mm to 54mm. The adapters are sold individually or in a pack of three for a particular size of motor. Each adapter has a floating forward closure that recesses into the motor and a retaining ring that threads into the motor case. Aluminum spacers hold the float forward closure and retaining ring together. The float forward closure is used to adjust the burn time, while the retaining ring and spacers are for a variety of different motor diameters.