Motor Run Capacitors What Are They?

Motor run capacitors, also known as AC capacitors, are an essential component in many electrical motors and HVAC systems. They serve a specific purpose in ensuring the smooth and efficient operation of these systems and their proper functioning is critical to their overall performance. In this blog post, we will delve into what motor run capacitors are and what they do, so that you can have a better understanding of this important component.

What are Motor Run Capacitors?

A motor run capacitor is a type of capacitor that is specifically designed to work with AC electric motors. It is a small, cylindrical device that is capable of storing electrical energy in a magnetic field. Unlike other capacitors, motor run capacitors are designed to withstand the high temperatures, high voltages and high frequencies that are common in AC motors.

What Do Motor Run Capacitors Do?

The primary function of a motor run capacitor is to improve the performance of AC motors. AC motors rely on a constant flow of electrical energy to keep them running smoothly, but this flow is often disrupted by the natural impedance of the motor’s winding. A motor run capacitor helps to overcome this impedance by storing energy in its magnetic field and then releasing it at exactly the right time. This ensures a constant flow of electrical energy to the motor, which helps to improve its efficiency, reduce its operating temperature and extend its lifespan.

In addition to improving the performance of AC motors, motor run capacitors can also be used to correct power factor in an electrical system. Power factor refers to the ratio of real power (the power used to do work) to apparent power (the total power delivered to a system). When the power factor is low, it can result in inefficiencies, such as increased energy costs and can even damage other components in the system. A motor run capacitor can be used to improve the power factor by compensating for the reactive power that is drawn by the motor, which helps to reduce energy waste and improve the overall performance of the system.


Motor run capacitors are an essential component in many electrical motors and HVAC systems. They serve a critical function in improving the performance of these systems by ensuring a constant flow of electrical energy to the motor and correcting power factor. If you have an AC motor or HVAC system, it’s important to have a good understanding of how motor run capacitors work and their importance in ensuring the smooth operation of these systems.

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