Poll: What is the Primary Benefit of a Variable Frequency Drive?

Variable frequency drives (VFD) provide speed or torque control for three-phase AC motors in variable and constant torque industrial applications such as conveyors, fans, pumps, and precision machinery.

Poll Question: What is the primary benefit of a VFD?

Top Comments

dougw over 5 years ago +4

speed control?
Robert Peter Oakes over 5 years ago in reply to dougw +4

yup.... I just ticked Frequency Control because thats what it does in order to achieve Speed Control
mp2100 over 5 years ago +3

Yes, speed control. My other answer is: injecting bad harmonics into the grid. Our experience is vendors don't do a good job rejecting the harmonics, so we add protection to our other equipment. For speed…

slocumjared over 5 years ago

at work we mainly use them for the speed control allowing for run freq, acel/decel freq plus dc brake.
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robogary over 5 years ago

even ancient VFDs provided open loop v/Hz speed control,
cheap & dirty modern VFDs are even better for speed control providing slip compensation ( like DC CEMF regulators) and sensorless vector algorithms
along with S curve and E curve ramps, the VFD babies the mechanics for longer life , less audible noise (fans) , more precise control of process variables
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a531016 over 5 years ago

100%, speed control. That is their primary function. The question is what you do with that, and some of the advanced features that are often onboard. With the right VSD andd the right IO you can build a self contained control system.

Some of the more advanced stuff surrounding energy management, measurement, system control even predictive failure - that's where it get's fun!
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Fred27 over 5 years ago

Another vote for speed control. Why is IoT even an option?
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kmikemoo over 5 years ago

Constant torque at variable speeds. 100% rated torque at 0 RPM is pretty impressive. VFD's also provide a means to limit motor starting currents. All of this at the cost of some impressive harmonics. If you are using VFD's, don't forget the line reactors. These solve a lot of harmonic issues.
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mp2100 over 5 years ago

Yes, speed control. My other answer is: injecting bad harmonics into the grid. Our experience is vendors don't do a good job rejecting the harmonics, so we add protection to our other equipment.

For speed control VFD is great when one pump size is too small and the next size up is too big.
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DAB over 5 years ago

There are a number of uses for VFD.

It was the major control factor for my telescope where you needed to maintain different rotation rate depending upon what you were tracking.
Planets required a different frequency as does the sun, the moon, the stars, comets and satellites.

VFD allows you to maintain more precise rotation of the motor where as PWM does not.

DAB
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Robert Peter Oakes over 5 years ago in reply to dougw

yup.... I just ticked Frequency Control because thats what it does in order to achieve Speed Control
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dougw over 5 years ago

speed control?
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