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Losses in VFD

08/25/2017 3:04 AM

What are the losses in VFD (Variable frequency Drive)..?

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#1

Re: Losses in VFD

08/25/2017 3:55 AM

Heat and noise.

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#4
In reply to #1

Re: Losses in VFD

08/25/2017 12:24 PM

You left out smoke! If done incorrectly, it might have a significant smoke release.

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#15
In reply to #4

Re: Losses in VFD

08/29/2017 3:19 AM

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#18
In reply to #4

Re: Losses in VFD

08/31/2017 2:57 PM

And money - They cost more than a contactor. JHF

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#2

Re: Losses in VFD

08/25/2017 4:22 AM

...and a small amount of light.

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#3

Re: Losses in VFD

08/25/2017 12:17 PM

Used properly, or used at all, the internet is the best source of information/instruction in our world.

Power losses from VFDs T

he power losses from VFDs can be generated by power electronic devices (converters) that convert the input voltage and current to the desired variable output voltage current.

Different topology of these devices in the VFD produces different properties, including output harmonic distortions.

Converter Losses – Conduction loss in the switching devices, which is proportional to the current, and switching losses, which are proportional to the current and switching frequency, are generated by the circuit components of VFD output power converter. Some VFDs also have an integrated transformer in the design.

This transformer contributes to the overall power loss of the VFD

From this website: Importance of Drive System Efficiency for Your Application

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#5

Re: Losses in VFD

08/25/2017 3:13 PM

Quantitatively, cumulative throughput losses are 2-4% at loads of >80%, as much as 20% at lower speeds and loads, but the percentage losses are as a percent of the load, so because the load drops with speed in centrifugal machines, that increased percentage is mostly insignificant.

Any kind of harmonic mitigation adds total throughput losses.

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#6

Re: Losses in VFD

08/26/2017 12:35 AM

Efficiency, some time power loss and hence money loss.

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#7

Re: Losses in VFD

08/26/2017 2:31 AM

Good question! I'm glad you came here, since this is an engineering site.

I'd like you to think about the answer and if you can't get it, then ask us. I'll show you how to attack the problem.

1. Determine what a VFD is and what it's made of.

2. Since a VFD converts a signal, there will be some sort of loss. AC to DC will be lossy, right.

3. Ask yourself where the loss comes from. Which components are involved and what losses do they have. Transformers? Resistors? Caps? Silicon? Circuit board? Tubes?

4. We know the output of a VFD is _____________. Somehow the current is changed from DC to _________. Repeat #3 for the conversion from DC to the output.

5. After you're done, take your project to the lab and test it.

In many applications, a VFD is suppose to help the efficiency of a factory/building. If this is true, then is this some sort of magic device? We know that it's lossy, so how does it increase efficiency. Here's your answer: http://www.ecmweb.com/harmonics/4-1-1-variable-frequency-drives

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#10
In reply to #7

Re: Losses in VFD

08/26/2017 7:25 PM

Auto broker:

According to this guy, vfd is a magical device.

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#12
In reply to #10

Re: Losses in VFD

08/28/2017 5:47 AM

Did he really say it's a magical device? And is he an engineer or some sort of salesman?

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#8

Re: Losses in VFD

08/26/2017 11:57 AM

42

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#9
In reply to #8

Re: Losses in VFD

08/26/2017 5:50 PM

You forgot to integrate the thermal transfer equation. And don't forget to use the natural log!!!

The correct answer is 4.

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#13
In reply to #9

Re: Losses in VFD

08/28/2017 9:18 AM

How come I keep getting 3?

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#19
In reply to #13

Re: Losses in VFD

09/14/2017 3:16 AM

You need to conjugate the dangling participle! If you don't, you won't get 4.

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#21
In reply to #19

Re: Losses in VFD

09/14/2017 2:23 PM

I, we, you, you, he, she, it, we all sh****.

I beg your pardon, my participle is not dangling, and my shorts are clean.

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#22
In reply to #21

Re: Losses in VFD

09/29/2017 1:31 AM

Yeah, but did you get 4 this time?

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#23
In reply to #22

Re: Losses in VFD

09/29/2017 9:58 AM

Nah, I just had bought two (the front ones), and had the one leaker on the rear plug and patch repaired.

Now I have another leaker on the right rear, but this time I was able to get most of a can of Fix-a-Flat in there, and aired it up - no further problems - yet.

Yet is always a keyword when it comes to automobiles.

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#24
In reply to #23

Re: Losses in VFD

09/30/2017 10:20 PM

Try some of this stuff. They say it'll fix anything! I saw a commercial where he sawed a boat in half, then taped it together and used it on the lake! I think you can stick some of this stuff over the plug or patch.

And see where it says it'll work on automotive stuff - just to the right of the flag!

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#25
In reply to #24

Re: Losses in VFD

10/02/2017 9:49 AM

I know I had zero luck with FlexSeal spray white over concrete water bowl for dogs. It would not adhere to the concrete (well cleaned and wire brushed).

So, no thanks, on that stuff.

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#26
In reply to #25

Re: Losses in VFD

10/03/2017 3:41 AM

A couple months ago, when I came home after a day at the office, I saw some of this stuff on our kitchen counter. My better half bought it! I think she saw the infomercial and thought it was good stuff. It's been in the garage in the area known as "stuff I may use someday in the future".

If you want to coat a surface that's going to get wet, try this stuff. I use it on the base of our swamp coolers. The base is where they rust out, so I paint this stuff on. Works great!

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#11

Re: Losses in VFD

08/27/2017 9:02 PM

The naysayers are usually objecting to what are actually false claims made by overly zealous sales people. VFDs do save very significant energy in SOME SPECIFIC SPPLICATIONS and those savings are documentable. But there is no magic involved for sure. Very simply, VFDs only save energy by allowing flow control in centrifugal machines where energy is wasted by some other means of flow control. That's because in reducing pump/fan speed to reduce flow, the energy reduces faster than it does with mechanical means of flow restriction due to the Affinity Laws. Even then, not every situation will result in energy savings, it needs to be properly studied.

Anything other than that and all you are really doing is reducing work preformed, meaning that even though less energy is used, more time is consumed so the energy per unit of work accomplished is constant.

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#14

Re: Losses in VFD

08/28/2017 9:27 PM

Sir,

VFD manufacturers will list the "waste heat" the VFD produces while it is working. When placed in an enclosure this waste heat must be transferred to the outside of the enclosure or else the electronics of the VFD will be harmed. As a general rule of thumb, for every 10 ºC temp rise over the design temp the electronics' life is cut in half.

Back to your question--this waste heat is your VFD's energy loss, so you should be able to calculate it as a percent of the total energy the VFD is handling. As some others have mentioned, there are some other types of losses, but I suspect they are not the primary one you are interested in.

--JMM

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#16

Re: Losses in VFD

08/29/2017 3:20 AM

Everything that passes through a VFD eventually ends up as heat.

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#17
In reply to #16

Re: Losses in VFD

08/29/2017 10:15 AM

Are you certain? Then why use a VFD at all, if no external work is done (all ends up as heat).

Bad analogy. Everything you eat eventually turns to what now?

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#20
In reply to #17

Re: Losses in VFD

09/14/2017 3:21 AM

To some, the answer is fertilizer - something that helps plants grow. To others, the answer is waste, something that fills up our landfills and sewers.

It's all in the eyes of the beholder.

I think this will help you get the point. To some, Jimmy Carter was the best POTUS every (what's that state above Florida?). To others, he was a weak, ineffectual, bleeding heart, tree hugger, who nearly destroyed our country - thank heavens Mr. Reagan was there to help!

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