What is the Service Factor? An In-Depth Guide

What is the Service Factor? An In-Depth Guide

Logistics and supply chain management is one of the most proficiently growing sectors today, with estimations of the global market expanding at 11.1% CAGR from 2023 to 2030. Learning the aspects of the service factor and gaining in-depth knowledge of the same is an integral part of logistics professionals. One may sign up for a logistic management course to understand the intricate details of service factor and how it helps professionals perform logistic management

However, various explanations surround the topic of the service factor in the industry. Some believe that the service factor aims to allow for brief explorations into overload events. In contrast, others opine that service factors are a sanction for carrying out the job of ongoing overload. 

In practical terms, it is none. 

Read on to understand what the service factor is and how it works.

What is the Service Factor?

The National Electrical Manufacturers Association (NEMA) defines the service factor as a multiplier that projects the minimum ratio between calculated capacity and any system's average transmitted load. The service factor portrays a tolerable and admissible power loading that may be performed under certain circumstances when put in an application with a rated power.

The concept of the service factor establishes that under normal operating circumstances, a motor can potentially cope with overloading up to a certain point within the insulation class. If the load increases, the current will also increase, resulting in the operating temperature or heat of the system (motor).

The service factor attempts to compute the external features that impact the performance of the motor and lead to malfunction or breakdown in the gear motor. When the motor is continuously operated at the top of its rated load, it tends to diminish the motor's service factor.

How Does Service Factor Work?

According to the NEMA standards, SF should indicate the service factor of a motor on its nameplate. More specifically, the MG-1 standards define the SF for generators and motors regarding speed and power. The MG-1 standard additionally provides a frame number linked to the service factor corresponding to every speed and power.

Consequent to the findings of an experiment conducted by NEMA MG-1, the estimated life of the motor windings decreases by half for every 10°C rise in temperature. However, the cause of the temperature rise is immaterial. The increase in temperature may occur due to low voltage, inappropriate ventilation, overload, high ambient temperature and so on.

How to Calculate Service Factor?

Any motor or device's service factor (SF) is generally expressed as a percentage or in decimal above the rated power of the motor or horsepower (HP). For instance, if the rated power of a motor is 10 HP with a service factor of 1.15, the motor will be able to handle 11.5 HP (10x 1.15 = 11.5) without any damage for a short period. 

However, the NEMA standards have specified a service factor of 1.0 for totally enclosed motors or gears. It implies that specific motors are designed to operate at a rated nameplate horsepower. Such motors are not to be overloaded beyond the specified capacity. 

If a motor is operated on a service factor greater than 1, it may suffer from several drawbacks that can negatively affect it. One of the main impacts of such practice is a rise in temperature and heat generation, which results from higher currents passing through the motor's windings. The integral parts of the motor may get deformed or break down due to thermal expansion, reducing efficiency and increasing the friction within the motor. 

Due to insulation degradation spurred on through heightened heat, ground faults and short circuits may also occur. Additionally, one must recognise the mechanical stress on the various components of the motors, for example, shafts and bearings. The increased heat causes the motor to depreciate faster and enhances the motor's friction, noise and vibration. All these are signs of premature wear and tear of a device, which means the motor has to be replaced even before its estimated life. 


Assessing the ideal load for a generator or motor is critical as it allows professionals to understand its service life better and improves its overall performance. The performance of electric motors may degrade up to 50% because of constant overloading, making it a significant concern for these motors. Overrating of the system is the most prevalent issue, but underrating may prove to be equally damaging.

If you are a logistic professional, understanding these intricacies is very crucial. For a successful career in logistic management, consider signing up for the Advanced Certification Program In Digital Supply Chain Management by Imarticus. This course will polish your theoretical understanding of the subject and enhance your ability in practical applications. 

Share This Post

Subscribe To Our Newsletter

Get updates and learn from the best

More To Explore

Our Programs

Do You Want To Boost Your Career?

drop us a message and keep in touch