Understanding the Function of a Fan Motor

Fan Motor

Understanding the Function of a Fan Motor

A fan motor is a key part of your HVAC system and it is important to understand its function and how it works. Moreover, the sooner you can recognize signs of a bad fan motor, the faster you can get it fixed by a professional.

Electrical protective devices such as fuses and circuit breakers are installed to protect the motor from overheating of its control gear or connecting wiring. These are essential for preventing expensive repairs.

Heat Dissipation

A fan motor is an essential component of your air-conditioning system, as it helps to produce cool air by absorbing heat from the outdoor environment and expelling it back into the indoor atmosphere. However, as it performs its role at full capacity, the Fan Motor motor can become hotter than normal, which can lead to premature failure and reduced performance. To prevent this, a motor-fan assembly should be designed for high efficiency and performance to limit the self-generated heat.

A good way to reduce the temperature of a motor is to use a large, thick heat sink. This will help to dissipate the heat generated by the motor, resulting in lower temperatures and a longer lifespan for the unit. A heat sink can be made from a variety of materials, including aluminium and copper.

Another way to reduce the heat generated by a fan motor is to apply a thermal filler, such as an epoxy resin. This will help to spread the load range over the entire speed spectrum, and can also reduce power losses by extending the load crest factor (CCF) of the machine.

Moreover, the cooling system of a fan motor can be improved by covering the external surfaces of the motor with a high emissivity layer and installing a radiator on the housing. These measures can decrease the temperature of the motor windings by up to 30 K compared to the configuration without the heat dissipation improvement concepts.


When a fan motor is operating, it produces a noise called rotational sound. It also creates a turbulent sound component which is caused by turbulence of the wind flow. The sound generated by the fan can be reduced by changing its rotation speed or optimizing the shape of the blades. In addition, a porous material can be used to reduce the noise produced by the fan.

If a ceiling fan is making scraping sounds, it could be due to the blades brushing against the frame of the motor. This could be a sign that there is something wrong with the fan or that the blade screws are loose. It is important to tighten the blade screws so that the fan is not making scraping sounds.

Another way to reduce the fan noise is to use acoustic barriers to enclose the source. These can be made from porous materials that absorb sound waves and convert them to heat energy. The barrier should completely enclose the source to reduce the sound levels. However, these barriers may limit airflow or raise the temperature of the motor and should be used carefully. In addition, acoustic barriers can be expensive and require specialized installation techniques. However, they are an effective way to reduce the noise generated by a fan motor.


The most significant characteristic of a fan motor is its ability to convert electrical power into mechanical energy. Electrical losses in the motor are a combination of magnetic energy dissipated by currents flowing in copper windings, iron losses due to leakage and lamination, and mechanical loss from bearing friction. These losses are known as stray losses and reduce the overall efficiency of the motor.

For this reason, fan motors should never be operated over-loaded, even for short periods of time. Overloading can cause excessive heat and damage the motor, significantly reducing efficiency and lifespan. Most motors are designed with a service factor that allows for over-loading to some extent, but this should be used sparingly.

Many factors drive the need for efficient motors, including financial and regulatory incentives, a desire to differentiate a building or brand, and the desire to achieve prestigious environmental certifications. However, in some cases, less predictable circumstances can also drive the need for more efficient motors. For example, the COVID-19 pandemic might prompt some building owners to increase air filtration systems from MERV-8 to MERV-13, which can require more powerful fans to maintain programmed airflow.

Infinitum Electric has developed a new evaporator fan motor technology that could dramatically reduce energy consumption in these applications. The new motor uses an advanced patent-pending controller that replaces the commutator and brushes found in standard direct current (DC) motors with a maintenance free EC-controller PCB. Infinitum has conducted field demonstrations comparing the new motor Fan Motor technology to shaded pole, PSC and EC evaporator fans in identical refrigerated display cases, measuring not only fan motor power consumption, but also display case discharge and return air temperatures and ambient store temperature.


The fan motor in your air conditioning unit is one of the components that puts the most stress on your entire system. It must endure continuous operation under high temperatures for years at a time to keep your home cool. However, it also needs regular maintenance to keep up its performance capabilities. This simple task helps prevent overheating, which is a common cause of AC fan motor failure.

The first thing a technician will do when troubleshooting a fan motor is check the capacitor. If the breaker is frequently tripping, this may indicate a short in the capacitor’s windings. A technician will also test the windings for a resistance reading. If the meter shows a zero or infinite reading, this indicates open windings, which require replacement.

Dirt build-up is another common reason for fan motor overheating. This dirt can block the holes in and around the motor, creating more friction and stress for the inner workings. To prevent this, have a HVAC professional routinely dust the motor and clean the vents around it. Getting this done regularly can prolong the fan motor’s lifespan, as well as help you avoid more serious AC problems in the future.

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