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If you’ve ever listened to a cheesy car commercial, chances are you’ve heard the term “torque” and “horsepower” thrown around.

In the industrial automation industry, even though the concepts are technically the same, determining the required RPM, Horsepower and Torque is paramount to the final decision.

Let’s start with some simple definitions:

Horsepower: A unit of measurement of power used to rate how much work is done.

One Metric Horsepower = the power to raise a mass of 75 kilograms against the Earth’s gravitational force over a distance of one meter in one second

Power: The rate of doing work, the amount of energy transferred over time.

POWER = (FORCE X DISTANCE) / TIME

Energy: The capacity to do work…that’s it! Energy may come in many forms including mechanical, thermal, and electrical.

Work: The measurement of energy transfer which occurs when an object is moved over a distance by an external force at least part of which is applied in the direction of the displacement.

Force: The term used to describe and measure an interaction that causes a change in an object’s motion

Remember Newton’s “3 Laws of Motion”?

Speed: When referring to induction motors, speed refers to the rate that the motor is working. Typically represented by Revolutions Per Minute (RPM)

Ok, I’m sure many of you are wondering why Torque has yet to be mentioned, especially when it’s in the title. It just seems easier to explain the whole concept of torque after clearing up some definitions first.

Torque: A specific type of work that acts upon an object causing it to rotate around an axis. Basically, the force that makes something spin, twist, or turn.

Still following? Great! We’ve got a few more terms to throw at you that will come up when looking for a new motor:

Locked Rotor Torque (aka Starting Torque): The minimum torque developed when the motor is at a stand-still. This will be an important factor to include as applications such as displacement pumps, cranes or conveyor belts will require a higher locked rotor torque compared to a centrifugal or irrigation pump.

Full Load Torque: The torque needed to produce the motor’s rated horsepower at full-load speed. This is generally found on the motor’s nameplate or datasheet.

Pull-Up Torque (aka Starting Torque): The torque developed when a motor is accelerating from zero to full load.

Breakdown Torque (aka Starting Torque): The highest torque potential the motor can obtain while running at the rated voltage/frequency. Basically it’s the motor’s max-out point.

Right about now you’re probably wondering what all of this has to do with selecting a motor.

It all comes down to the relation between…

Torque, Horsepower, and RPM

Our tech support generally hears a lot of similar questions: “I want this to go faster,” “I need to ramp up the production,” “I need a bigger motor to handle heavier loads.” The common misconception is that increasing one of the three variables will increase all of them, not so! Sooooo, what now?!?

With some help from our engineers we were able to visualize the relationships between RPM, HP and motors a little better. Ramping up your RPM might not actually be the solution you’re looking for if more power is what you need.

Just imagine a semi-truck versus a corvette, they may have the same amount of HP, but only one will be able to tow a trailer…while sacrificing speed.

The same can be said for electric motors! 

If you keep the HP the same, you will lose torque if you use a faster rated RPM motor.

Now that we have a better understanding of what torque really is and its relationship with HP and RPM the world of motors should be a little less mysterious. Feel free to contact our tech support at techsupport@wolfautomation.com for assistance in sizing your next motor.

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Visual thinker in a digital spectrum, or in layman’s terms….I make all the visual content for Marshall Wolf Automation 🙂 With a background in video advertisement and film production, I work with MWA’s marketing department to keep our customers reading our blogs and viewing our products.

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