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Motors are essential components in our daily lives, found in electrical appliances, industrial equipment and vehicles. But did you know that the "motor output," which represents motor performance, is influenced by various underlying conditions?

In this column, we'll explain the concept of ‘rated output’, one of the most important aspects of motor performance, in three installments.

1.What is Motor Output?

Motor output is a fundamental indicator used to evaluate motor performance. Specifically, it refers to the mechanical energy that a motor can produce, determined by the relationship between torque, which is the force twisting the motor shaft, and motor rotational speed.

This relationship can be expressed with the following equation:

 Motor Output [W] = Motor Torque [Nm] × Motor Speed [rad/sec]

(Note: [rad/sec] is calculated by multiplying the rotational speed in RPM (revolutions per minute) by 2π/60.)

2.About Motor Efficiency

From the perspective of electrical energy and efficiency, motor output can also be expressed as the product of the electric energy input to the motor and motor efficiency, which is electrical-to-mechanical conversion efficiency.

The formula is as follows:  

Motor Output [W] = Electric Energy Input [W] × Motor Efficiency [%]

Motor efficiency plays a vital role in utilizing electrical energy effectively.

For instance, in 2023, Japan's total electricity demand is estimated to be 850TWh, with industrial motors consuming approximately 40% of this energy—equivalent to around 340 TWh.

It means that even a 1% improvement in efficiency of industrial motors could eliminate roughly 3.4 TWh of power consumption.

To put this into context, saving 3.4 TWh is equivalent to generating the same energy using solar panels covering approximately 3.4 square kilometers as big as Central Park in New York, or equivalent to around 470 soccer fields. These examples demonstrate just how significant improving motor efficiency—even by just 1%—can be.

3.About Motor Losses

Next, let’s deep dive into motor losses. Losses are represented by the following equation:

 Losses [W] = Electric Energy Input [W] – Motor Output [W]

 Losses refer to the portion of input energy that cannot be utilized as output power. It is generated from electrical resistance and friction, both of which cause to the motor's temperature rise.

Additionally, motor losses can also be described using motor efficiency as follows:

 Losses [W] = Electric Energy Input [W] × (1 – Motor Efficiency [%])

From this formula, it’s clear that higher motor efficiency results in lower motor losses.

In the next article, we will explore how losses and temperature rise impact motor performance and why ‘rated output’ is so important. Please stay tuned!