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Hi Adam Ring with Innovative IDM. Now a lot of people often wonder what’s the difference between constant torque and variable torque applications in relationship with variable frequency drives. Well it’s really simple, if you think about as the speed varies for a given application if the torque remains the same, regardless of the speed then that’s considered a constant torque. An example of that might be a conveyor. If a conveyor is running really, really slow, you’ve got a given torque with a given load, as long as that load remains the same if you speed it up it still requires the same amount of torque to move it.
With a variable torque application the torque actually varies with the speed so for example a fan or a pump. Takes a very, very little torque to turn a fan at a very low speed. But as that fan starts to speed up and its pushing more air, then it requires more and more torque to push that load and so we call that variable torque. Now typically when we’re talking about sizing a VFD. They’re designed for a given amount of overload capacity in order to start a load, and so typically for a constant torque application, because it got the full demand of torque right at the start up they’ll give you 150% of overload capacity for 60 seconds. With a variable torque since when you start there’s very little torque requirement we only require 120% overload capacity for 60 seconds.
So if you’d like to learn more information about variable torque and constant torque applications or other questions about variable frequency drives please give us a call or look us up at innovativeidm.com were the home of the legendary customer experience