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June 25th, 2008 admin Leave a comment Go to comments

Understanding Induction vs. Universal Motors in Your Electric Power Tools

As a woodworker you've likely not given much thought regarding the two primary types of motors used to power your electric woodworking tools. The differences in performance - and the number of zeros on a price tag - should have your attention.

As in all considerations regarding power tools your ultimate decision should be based on your projected USAGE. If you're a newbie just getting started then it might not be time to invest in the cast iron induction-powered table saw. If you're running a professional shop then all six of your table saws probably have induction motors.

Your duty to yourself as a consumer is to make educated decisions. In that interest here are some of the differences between induction and universal motors... without getting too technical and without taking a "one motor is better in all situations" stance.

1) Size and Weight
Induction motors are typically heavier than universal motors, making them ideal candidates for stationary tools that need the extra weight anyways to reduce rattling and improve stability. Obviously at their weight and size they make poor candidates for hand held or portable tools.

That's where universal motors come in to play. Their smaller size and weight make them ideal for circular saws, bench top planers and your shop vacuum.

2) Cost
Induction motors are more expensive and found often these days in the top of the line electric power tools. They're made with more copper, aluminum and steel than universal motors. Universal motors are less expensive and found in just bout every electric power tool known to man.

3) Speed
Induction motors typically have a slower max speed. Universal motors are only limited by friction.

4) Torque at Start Up
Induction motors have less torque at start up - think of them as "high gear" on your car or bicycle. Once they're at cruising speed they're good to go, but typically don't much like to be stopped and started frequently. Universal motors typically have great torque at start up that get blades chewing through tough spots. They can cruise too but that leads us to...

5) Longevity
Induction motors are long-lived. There are stories of woodworkers using induction motor powered tools passed on by their grandfathers. Universal motors are more likely to burn out in a shorter period of time. There are stories of universal motors lasting for 20 years and more, but as a very general rule universal motors don't last as long as induction motors.

6) Noise
Induction motors are quieter - far far far quieter - than universal motors. Universal motors are widely known for their shriek and many residential areas have bans on their usage after a certain time of day. (Note: you should wear hearing protection while using either one...)

7) Standardization
Induction motors have been standardized by NEMA. This means that it's easy to replace induction motors in your machines with standard motors from different manufacturers due to standard frames, shaft sizes, mounting dimensions and more. Universal motors are typically characterized by their LACK of standardization, which can sometimes makes replacement difficult.

Energy Efficiency
Induction motors are highly efficient motors that require less amperage per horse power. Universal motors require more amperage per horse power than induction motors. All this extra energy requirement turns into heat in the motor which will sometimes burn them out - literally - if used for extended periods of time.

9) Application: Your Final Decider
Ultimately whether you purchase a tool where there's actually a choice between induction and universal (table saws and planers for example) you will have to ask yourself how often you'll be using the tool and your likelihood of continuing with your hobby.

Your induction motor tools will have a higher resale value if you bail out of woodworking, but will cost you more in the upfront. Your universal motor power tools will have less of a resale value but cost less upfront.

If you walk into your hardware store with a basic understanding of the two major types of electric motors along with a firm idea of what your woodworking projects will be for the next few years you're going to walk away with the right tool for you. And that's the most any woodworker can ask for.

About the Author

Garrett French is the Editor for ToolCrib.com.

At www.ToolCrib.com you can find and compare tools, catch up on the latest topics and debates at the power tool blog and save tons of money on power tools by subscribing via rss or email to our power tool deal of the day.

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