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Miniature Electric Motors: Speed and Torque in Focus

A DC motor's speed and torque are crucial performance factors for the successful and efficient operation of the application or device being powered by the mini motor. Speed is usually considered a function of torque, with the motor operating the application at a specific torque and speed. However, these two characteristics must be balanced; motors normally produce less torque when operated at greater speeds, but in certain circumstances, the motor may need to operate at a considerably greater speed but with less torque or may require a motor to accelerate, which would require a larger torque at a faster speed. Let’s dive into these key motor features more in detail and explore how they impact the motor selection process.

Speed Characteristics of Mini Motors

A miniature motor's speed is defined as the magnitude of the rotational velocity of the motor shaft. Dictating how quickly the motor’s axis rotates, the output speed requirements should be one of the first features that are considered when developing a new product or working towards a new iteration of a current application. Keep in mind that these speed requirements will vary depending on what needs to be moved and how well the other parts of the machine are coordinated; you should also be able to answer how quickly the motor must turn to power the application's mechanism, as well as if different speeds need to be accommodated.

Below are three broad suggestions that can assist you in selecting the right motor technology for your application:

  • Brushless DC Motors: Ideal for applications requiring 10K RPM or greater. These are best suited to operate at greater speeds due to the design and electrical commutation of their components.
  • Brush DC Motors: Ideal for applications between 1K and 10K RPM. High-speed brush DC motors present a commutation system difficulty since brush wear increases at high speeds and leads to a shorter life. With that said, Portescap’s ironless brush DC coils allow for both high acceleration and higher speeds, especially when compared to the iron-core brush DC designs.
  • Stepper Motors: Ideal for applications less than 1K RPM. Although steppers are electronically commutated, due to their increased number of pole pairs, they are not intended to operate at high speeds. However, our disc magnet motor series features a thin disc magnet as opposed to a cylindrical magnet. By lowering the inertia of the motors, this unique step motor range can achieve speeds up to 10,000 rpm.

Keep in mind these speed ranges are only suggestions - there are ways to apply various technologies in various speed ranges!

Torque Characteristics of Mini Motors

Torque is the amount of rotational force that a motor generates during operation. In a given application, the torque for each axis is defined by the specific requirement in the machine, which is required to move the object driven by the motor. The torque requirement of the axis determines the size of the motor and any gearing necessary.

The motion system's required output torque is the next characteristic that needs to be accounted for. Consider the following questions:

  • What level of constant torque is needed during operation?
  • Is there a peak torque for a brief period that must be taken into account?
  • Is the safety margin large enough to offset the other application factors?

The safety factor is the first thing to think about after you have determined the torque requirements for your application. To account for friction buildup, wear, etc. over time, a standard safety factor is 50%. The next step is to compare your final torque figure to the maximum continuous output torque for each motor technology. It's possible for different technologies to provide the required output.

If the output torque value is higher than the maximum for the motor alone, you will need to add a gearhead to the motion system to boost the output torque capacity. Reduction ratios on gearheads are a representation of the motor's output torque multiplied by the gearbox's effectiveness. This works well for applications that need a larger output torque value, but the output speed is reduced in line with the ratio.


Speed and torque are part of the motor’s load operating points, and they should be considered together with the motor's performance limits. Having this knowledge will make it easier for you to choose the best motor for your needs. However, keep in mind that the above speed and torque discussion is only intended to provide a broad overview of these characteristics; consulting with a trusted motion provider like Portescap at the earliest stage of application/device design process will ensure that all application requirements are considered – and the ideal motion technology is created (and customized!) for you. Reach out to Portescap directly to discuss.

Hi! I'm the Global Content Manager at Portescap, where I work closely with our Engineering, R&D, Product Management, and Business Development teams on crafting content related to the world of miniature motors. I have almost a decade of experience in digital marketing, specifically in the B2B industrial manufacturing space - here's to many more years of learning and talking about mini motors!
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