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As the motor or gear motor selection process begins, the designer must gather the relevant technical and commercial requirements

Image: Shutterstock

Gears & Motors Selecting a gear motor in 4 simple steps

Jun 5, 2018

With umpteen motors and gear motors promising to be the “most efficient” or of “the highest quality”, the choice can be a difficult one to make for design engineers, who are selecting components for an application. This article highlights how enterprises can select a suitable gear motor for a particular application in just four simple steps.

For design engineers who are in the process of selecting components for an application, the motor or gear motor can be one of the more difficult components to source, with so many options to choose from. So, here are four simple steps to lead designers to the best motor/gear motor choice for a specific application. There are numerous key design parameters that should be considered when selecting a motor or gear motor for a motion control application.

Gathering design inputs

As the motor or gear motor selection process begins, the designer must gather the relevant technical and commercial requirements. However, this first step is often overlooked, which happens to be a critical component in the design process. The gathered design inputs information will then be used in the selection process and will dictate the ideal motor for the application.

Failure to gather the proper inputs can lead the designer down an untended path. This is why it is helpful to use the Application Checklist (Table 1) when developing the motor specification. These parameters, along with some project specific requirements, will be helpful when navigating the selection process.

Selecting each motor

Next, the designer must consider what type of motor technology best suits the intended application. Using the design inputs, the Motors Quick Reference Guide (Table 2) can be used as a selection matrix in the first step of the decision process. This reference guide details four common motor types and provides general information to take into consideration when selecting each motor.

Since each application has its own unique characteristics, it is important to determine which of the parameters (for example, horsepower, efficiency, life, starting torque or noise ratings) are most important to the application under consideration. During the motor selection process, by looking at the required speed and torque of the application, it should become evident to the designer if the motor chosen requires a gearbox to meet the necessary requirements. If a gear motor is necessary for the application, another level of complexity will be added and several additional criteria will need evaluation.

Conceptually, motors and gearboxes can be mixed and matched as needed to best fit the application. Yet, in the end, the complete gear motor is the driving factor. There are a number of motors and gearbox types that can have an amalgamation – for instance, the right angle worm, planetary and parallel shaft gearboxes can be combined with permanent magnet DC, AC induction, or brushless DC motors.

Integrating gear motor into system

Though there are a vast number of different motor and gearbox combinations available, not just any one will work for the application. There will be certain combinations that will be more efficient and cost-effective than others. Knowing the application and having accurate ratings for the motor and gearbox is the foundation for integrating the gear motor into the system effectively. Hence, as the designer looks at selecting a gear motor, there are two methods that can be used. The first method involves selecting motor and gearbox separately and assembling. The second method involves selecting a pre-engineered gear motor. While both methods are an effective means of finding the most compatible gear motor, the second method reduces design time and project risk for the designer.

When selecting a pre-engineered solution, the manufacturer has done much of the heavy lifting to ensure that the motor and gearbox combination will work properly together. Since the manufacturer has completed performance calculations and testing, gear motor failures caused by miscalculations or improper component matching will be minimised. Due to the complexity of the first method, this article focuses on the second method.

Matching the application needs

Once again, looking back at the gear motor performance data gathered from the Application Checklist (Table 1), the speed and torque required for the application is critical in selecting the gear motor combination. Using the speed and torque measurements, the designer can then select the manufacturer’s performance curves that match the application needs. The gear motor curve (Figure 1) combines the performance of the motor and gearbox by displaying speed, torque and efficiency. If a complete gear motor assembly is purchased from a manufacturer, this curve is provided by the vendor.

Reviewing design limitations

Finally, after selecting a few performance curves that appear to meet the application needs, it is important to review the design limitations. By looking for the following information in the manufacturer’s performance calculations, we can determine if the chosen gear motor will cause any issues within the application. The thermal characteristics include full-load gearbox torque, gearbox input speed, gearbox yield strength and intermittent duty considerations.

Once the gear motor has been chosen and installed in the application, it is critical to perform several test runs in sample environments that best reflect typical operating scenarios. If extreme motor heat, unnatural noises or obvious motor stress occurs, we may repeat the motor selection process or contact the manufacturer. It is vital that we take out the time and put in the effort to properly select a motor. If not done so, a hasty decision and lack of testing can cause a host of problems with the gear motor and could possibly damage the application. Although the gear motor selection process can be arduous, a properly selected gear motor can last for years and will optimise the application to its peak potential and efficiency. From a company perspective, an optimal gear motor will also reduce operating costs and increase plant productivity.

The article is reproduced with courtesy to Groschopp
For further information, contact: sales@groschopp.com

Image Gallery

  • Table 1: Application Checklist - use this checklist to help formulate the specific requirements to ensure the gearmotor vendor has the critical information necessary to achieve the best match between the gearmotor and the application

    Image: Groschopp

  • Figure 1: Gearmotor Performance Curves - the Speed / Torque and Efficiency / Torque curves for a PM gearmotor

    Image: Groschopp

  • Table 2: Motors Quick Reference Guide provides a comparison of common parameters used during the motor selection process

    Image: Groschopp

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