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How to Select the Right Gearmotor

Revised: 4/15/22
Grainger Editorial Staff

Untitled Document

gearmotor is an all-in-one combination of an electric motor and a gearbox. This makes it a simple, cost-effective solution for high-torque, low-speed applications because it combines a motor with a gear reducer system. Most importantly, gearmotors ensure a well-matched electric motor and gearhead, helping to achieve optimal energy efficiency in addition to extending the life of your equipment.

However, for many electrical and mechanical design engineers, choosing the right gearmotor can be a complicated and challenging process. There are many factors to consider when selecting a gearmotor. Whether you plan on purchasing a pre-engineered gearmotor or choosing a gearbox and a motor separately, understanding the various application requirements is essential to finding the perfect match.

1. Know your application requirements for your gearmotor: The first step in selecting a gearmotor is reviewing your application requirements. These include but are not limited to:

  • General requirements: Envelope size, mounting orientation, mounting type and size, overhung and side loads, shock load and lubrication type.
  • Input power source: Voltage, frequency (Hz), maximum current (Amps) and control type, if applicable.
  • Gearmotor specifications: Size, weight, desired noise level, life expectancy and maintenance level.
  • Gearmotor performance: speed, torque, duty cycle, horsepower, starting and running torque (full load).
  • Operation environment: Application and ambient temperature, and ingress protection (IP) rating.

2. Know the speed and torque requirements of the load to be driven: To ensure your gearmotor is properly sized for your intended application, it’s important to know your output speed, starting and running torque. Selecting the proper gearmotor is a matter of matching output speed (RPM) and torque to your application’s needs. The output speed is determined by your machine’s requirements and should be already known. That leaves the starting and running torque to be determined. Keep in mind, when you choose a pre-engineered gearmotor, the manufacturer has done most of the heavy lifting to ensure the motor and gearbox will work seamlessly.

Once you have calculated the starting and running torque needed, you will also need to review the gearmotor's potential design limitations, including the running (full-load) output torque, output speed, overhung load, shock load, thermal characteristics and duty cycles.

3. Select the proper motor: Next, use your list of application requirements and compare them to the motor specifications of the different types you are interested in such as a universalbrushless DCAC induction or a permanent magnet DC gearmotor. Because each application has its own unique characteristics and requirements, it is important to note which factor such as horsepower, starting torque or efficiency is most important to your application. During this phase, you may decide that matching a gearbox and motor separately will best suit your needs.

4.Test the motor: Once you have selected a gearmotor, it is important to run several tests to ensure the motor runs well in a typical operating environment. If the motor becomes unreasonably hot, is too noisy or appears stressed, repeat the motor selection process or contact the manufacturer.

Taking the time to properly size your gearmotor will help ensure that it will last for years and operate at peak efficiency.

The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.

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