How to Choose an Electric Motor: Engineering Tools

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Video Transcript

Hello, this is Janette and Joe  with Groschopp and we’ve reached our final video in the  “How to Choose an Electric Motor” series.  We’ll be sharing some tools to help you select the best motor for your application.

As we’ve mentioned in previous videos, speed, torque and power are the fundamental ways to rate a motor. Here are four equations to get you started. We’ve included a link below to download these.

The first equation is used to determine the relationship between speed, torque and power.

Use the second to estimate the current that will be needed to meet your application’s power requirements.

The third equation helps you determine the efficiency of your system. When there’s more than one efficiency in a system to consider, you multiply them together to get the total efficiency.

The final equation is to help determine the size of motor you’ll need. If you require a motor with higher continuous output power, you either need a larger diameter motor, a longer motor, or a different motor type that has a higher power density.

Now, to simplify these calculations we’ve developed a piece of software here at Groschopp called the STP Conversion Calculator. As you might have guessed, STP stands for Speed, Torque and Power.  There are two versions of the calculator available and they both use the formulas we just showed and and they convert units automatically.

The basic online calculator is accessible on our website and can be used for quick calculations.

By entering speed and power values, torque is calculated along with all common unit conversions for each value. It automatically generates the most common units.

For more detailed calculations we have a free downloadable desktop version that expands into estimates for electrical input losses and annual operating costs.

We’ve included the links to the STP Online and Desktop Calculators below.

Next we want to share several efficiency curves with you.

This first set include each of the four motor types we’ve discussed to help you calculate current draw.

These curves can be used together with the formulas or STP Calculator, to estimate the amp draw within your application.  Most of these graphs show two curves to represent the high and low efficiency range for each motor type.  

Next we have the same efficiency curves for the four most common reducer types.

As we already said, simply multiply the motor efficiency by the reducer efficiency to obtain the total efficiency for a gearmotor.  There’s quite a bit more we could say about reducers and gearmotors, but that’s for an entirely different series.

Our final tool to share is a compilation of the typical power factors for the different motor types we’ve covered.  

To get a truly accurate estimation of motor current draw, you need to figure in the power factor.

Before we finish up, let’s bring back a few other tools we’ve provided along the way.

We have the list of motor application criteria to help rank specifications for priority, and our motor reference chart. Both can be used to filter the motor types that are capable of meeting an application’s needs. Using the motor and speed-torque charts, you can compare the relative differences between motor types for your application.

We’ve included links below to download all the guides and charts.

Thanks for sticking with us through these ten videos.  We hope you feel equipped to confidently select a motor for your application, or at least know where to start. If you have any new products or are looking to change the motor in your current application, give us a call and our technical sales team and engineers will gladly assist you through the selection process.

For more information about Groschopp or any of our products, or for additional technical resources, check out our website at www.groschopp.com.

How to use the Motor Search Tool

Narrow your search by selecting motor type, gearbox, voltage, and phase options for your desired motor.

Select a dominant variable: choose one of the three parameters to narrow your search. The selected variable determines which slider bar you will be able to manually move.

Use the slider corresponding to your dominant variable to further narrow your motor selection. The other sliders will automatically move to show available ranges based on the range of your selected variable.

Results will upload as your search criteria changes. If you have any questions regarding your results or how to use the search tool, you can chat with us using the green tab on the left-hand side of your screen.

Note: Groschopp Universal motors are custom built to fit your application so no additional options are available to narrow the search. Selecting the Universal motor type will prompt a message taking you to the Universal product page.

Not sure what you need?

One of our team members would be happy to help. Contact us at 800-829-4135 or by email at sales@groschopp.com. You can also chat with us using the green tab on the left side of your screen.

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Universal Motors

Groschopp Universal motors are custom built to fit your application so no additional options are available to narrow the search. Standard frame sizes and motor features can be found on the Universal page.

go to Universal page