So are you saying the manufacturer who are supplying the product to the OP with line reactors acting as passive filters did not exercise the same care in selling as you did?
VFD Line Side Reactors
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My company was involved in the design, manufacture and the supply of variable speed drives since 1972. We did fit input reactors. Their purpose was not harmonic mitigation.So are you saying the manufacturer who are supplying the product to the OP with line reactors acting as passive filters did not exercise the same care in selling as you did?
I think we are done with this subject.
What else is the purpose?
Here is an article detailing purposes of line reactor for a VFD including its role in
reduction of harmonics on line side.
https://www.ecmweb.com/design/line-reactors-and-vfds
Check the figures. They confirm the point I hade about harmonic mitigation.
Interesting discussion. To be honest I did not question their reason for including the reactors - they were not specified, and there is not a (known) need for them from an IEEE 519 perspective - I was just reviewing the drawings provided for the equipment skid, and was concerned with location of the proposed reactors.
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Besoeker is right, the role of line reactors in harmonic attenuation is often overblown. In my experience they will LOWER the harmonics, from 40-60% THD down to 30-35% THD, basically the same level of attenuation you get by adding a DC bus choke. Adding a Line Reactor to a VFD that already HAS a DC bus choke only brings the 30-35% number down to 25-30%. But either way that is usually not enough to make a significant difference if harmonics are even a problem in the first place. If your total non-linear load is a fraction of the total load, the THD created by VFDs may be insignificant in the big picture, meaning as measured at the PCC per IEEE-519 requirements. My rule-of-thumb is that if your non-linear load is less than 30% of the total load, you may not need to worry about harmonics at all. 30% non-linear loading is the trigger point I recommend for getting a detailed evaluation done.
That's not to say line side reactors are unnecessary, I highly recommend them as "cheap insurance" for the rectifier of the VFD in most installations. To my mind, this is because their best purpose is in lowing down the rise time of line side transients coming in from the utility side that can cause damage to the diode bridge by adding an inductive time constant to the input. This is why one large reactor in front of all 4 drives could serve the same purpose as 4 smaller reactors. Even then, if your source impedance is high enough already, i.e. the source transformer kVA is less than 10x the VFD kVA rating, you have the equivalence of that anyway and a line reactor may not be necessary at all.
The other good reason to use reactors is when using Active Harmonic Filters as your harmonic mitigation strategy, because going from 40-60% THD down to 30-35% can often mean the difference in using one size smaller on the AHF and saving money.
I also disagree with the notion that Utilities require 5% line reactors... I have never had a utility dictate any hardware requirements. What they "dictate" is compliance with IEEE-519, how you get there is your business. 5% line reactors being required would put an undue burden on some applications, because at 5% you can see a voltage drop that MAY interfere with getting full torque from the motor.
That's not to say line side reactors are unnecessary, I highly recommend them as "cheap insurance" for the rectifier of the VFD in most installations. To my mind, this is because their best purpose is in lowing down the rise time of line side transients coming in from the utility side that can cause damage to the diode bridge by adding an inductive time constant to the input. This is why one large reactor in front of all 4 drives could serve the same purpose as 4 smaller reactors. Even then, if your source impedance is high enough already, i.e. the source transformer kVA is less than 10x the VFD kVA rating, you have the equivalence of that anyway and a line reactor may not be necessary at all.
The other good reason to use reactors is when using Active Harmonic Filters as your harmonic mitigation strategy, because going from 40-60% THD down to 30-35% can often mean the difference in using one size smaller on the AHF and saving money.
I also disagree with the notion that Utilities require 5% line reactors... I have never had a utility dictate any hardware requirements. What they "dictate" is compliance with IEEE-519, how you get there is your business. 5% line reactors being required would put an undue burden on some applications, because at 5% you can see a voltage drop that MAY interfere with getting full torque from the motor.
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See my previous post as the value of Line Reactors, they are a good idea in most cases. But to your earlier point, you are correct in that the individual reactors should be DOWNSTREAM of the OCPDs for the drives. If they go with one larger reactor, it can be up stream.
Thanks. Just to confirm - in order for the larger reactor to be installed upstream of the individual OCPDs, it would need to be rated at the upstream OCPD rating (in this case, 400A)?
Would this be covered by Article 470? Interestingly 470 does not specify overcurrent protection for reactors. Nor does the mfr documentation (at least the AB 1321 series docs I looked at). Besides engineering principles, what provides the requirements for OCPDs on line reactors? Is this something that would be specified in UL508A or other standard?
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This is a matter of some debate. I have always done it like this and have never been red-tagged:
- It would fall under Article 210 if the reactor is in the BRANCH circuit, defined as the OCPD being the last protective device before the load. So the 4 individual reactors, if put DOWNSREAM of the breakers, would be covered by 210.20 and all it implies and since the line reactor must be sized per the VFD input current anyway, the OCPD for the VFD covers the protection of the reactor.
- If done as one large reactor feeding the 4 separate drives, the upstream OCPD becomes a "Feeder", so 215.3 would apply, requiring that the OCPD be no more than 125% of the rated equipment. So the reactor would have to be rated for at least 320A (400A/1.25).
RumRunner
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A matter of debate perhaps. . . not as much as opening a kettle of fish.
It will beg for reactions (expressed or unexpressed) not only in this forum but the whole academia.
This forum has a wide reach in terms of readership. . . globally as a matter of fact. (thanks for the magic of Mr. Google)
Anything that we say here will live in perpetuity. . . and any opinion that we offer can be subjected to scrutiny.
This is not to say that one's opinion is a total hogwash. I won't say that one's opinion is hogwash simply because it is outside my line of reasoning.
This often misunderstood that reactors are solely for mitigating harmonics protection of VFDs-- which have been beaten to death in this discussion like a dead horse.
Reactors are there for several reasons which I will mention a few in relevance to this discussion.
1. Bringing the facility in compliance with utility standards.
2. Avoid litigation and damage settlements.
3. Improving true power factor.
4. Reducing cross-talk between drives.
5. Prevent fuse and circuit breakers from blowing and tripping due to high current spikes.
6. Protection of capacitors and other system components from harmonic resonance.
Above list is just a fraction of a complete list of reasons why reactors are there. It seems that most of what we see here is mostly evidence of posters being caught up with just one issue. . . the harmonics and their effects.
Seeing a full view of the forest is completely obscured because of the trees.
I will focus on the first three on the list since this presents contention on what I mentioned on my earlier post.
This was even made an issue.
OP's notion that reactors are rated like energy-consuming appliance is misguided. They are not rated on how much current they will draw like a motor for example.
Science had proven through earlier experimenters like Faraday, Newton and others that their studies that pertain to modern reactors help in reducing in-rush current and thus minimize nuisance tripping of OCPDs.
Reactors are rated in percent (%) of the voltage and current and are deployed-- based on what these reactors are intended to be used.
Hence, often mandated by energy suppliers. The City of LA requires power factor improvement and it is a must under penalty or surcharges if not complied with.
If I may invoke Newton's Law of Energy Preservation-- and further studies that resulted in Lenz Law which states:
“When electromagnetic energy is induced, the resulting EMF opposes the cause of its production.”
As with with all coiled wires, like reactors, it resists change.
Had this LAW never existed, anytime we turn on any energy consuming apparatus will endlessly continue to consume unopposed until all energy is either transformed to heat or dissipate into thin air.
Energy is not lost—it remains in the air. We cannot create energy, we can only transform it.
Thanks for Uncle Isaac and the German scientist Heinrich Lenz.
Further, how electromagnetic circuits obey Newton's Third Law of Motion--as presented in mathematical equations by Heinrich Lenz, offers us a better understanding of this third law of energy conservation by Newton.
Hallelujah!
OP doesn't have any notion they are rated like a motor or energy consuming appliance. They do have a current rating.
RumRunner
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:weeping:
You are asking for confimation
that provide requirements for OCPD on line reactors.
OCPD= OVERCURRENT Protective Device.
You are asking for confimation
that provide requirements for OCPD on line reactors.
OCPD= OVERCURRENT Protective Device.
what part of that question treats the reactor like a motor or other energy consuming device? A conductor requires OCPD too, but isn't a motor or energy consuming device. Reactors are rated in % impedance and current. I'm confirming how the reactor gets protected.
thanks, jraef.
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