Hot line reactor
Hot line reactor
(OP)
I recently installed four VFD's for four air handlers. These are 208v 3 ph motors from 10-20 hp. Three of four drives are running well. Motor currents and temperatures are good at 60 hz.
A 15 hp drive has a line reactor which is excessively hot at 60 hz. It does vibrate quite a bit as well.
I have tried two different reactors with the same result.
Motor currents are normal and the electronic drive does not appear to be having any problems. The system is working normally except for the hot reactor. Reactor current is about 75% of full load.
The supply conductors are about 125 feet long and oversized at #2 rw90.
The motor is original and not designed for invertor duty.
I performed a harmonic study on these systems as well as the building service. Although intrepreting the results are a little bit over my head, I am on the understanding there are no immediate problems with the results. THVD on this drive is about 1.6% and THID 55%.
I ran a separate ground wire #6 back to the station bus.
Any ideas?
Batfastard
A 15 hp drive has a line reactor which is excessively hot at 60 hz. It does vibrate quite a bit as well.
I have tried two different reactors with the same result.
Motor currents are normal and the electronic drive does not appear to be having any problems. The system is working normally except for the hot reactor. Reactor current is about 75% of full load.
The supply conductors are about 125 feet long and oversized at #2 rw90.
The motor is original and not designed for invertor duty.
I performed a harmonic study on these systems as well as the building service. Although intrepreting the results are a little bit over my head, I am on the understanding there are no immediate problems with the results. THVD on this drive is about 1.6% and THID 55%.
I ran a separate ground wire #6 back to the station bus.
Any ideas?
Batfastard





RE: Hot line reactor
RE: Hot line reactor
Reactors add impedance, i.e. 1-1/2%, 3%, 5% etc. etc. Since that impedance isn't creating electromotive force as a motor does (except vibration to a certain extent), it is dissipated as heat. As davidbeach alluded, your interpretation of heat may be well below the design tolerance of the reactor.
As to excessive vibration, first off realize that just like heat, there is always going to be some vibration, it is a magnetic device. It shouldn't be more than what you would expect from a transformer hum however. Excessive noise is usually a bad installation, bad manufacturing, bad design or a combination of any of the above. I have run across several installations where I had an excessively noisy one, replaced it with another of the same brand and saw no difference, then replaced it with a different brand and the problem went away. Most of the time however it has to do with the installation, a mechanical harmonic in the reactor vibration spectrum that interacts with something peculiar to that location. You can also try relocating it and making sure you have vibration isolation of some sort.
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RE: Hot line reactor
If not, its time for a new properly spec'ed reactor.
RE: Hot line reactor
The temperature in this reactor appears to be within limits.
What my concern is, there are similar reactors in other drives which are carrying more current (% of full load) and not near as hot as this one.
Could this be a symptom of something else not right in the system or just a case of not everything is created equal.
RE: Hot line reactor
Isn't 55% a little high?
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RE: Hot line reactor
I am on the understanding if these THID values are not causing problems elsewhere in the building, (phantom trips etc.) then maybe we can live with it. Please correct me if I am wrong.
I do not think it is the harmonics that is causing the line reactor to heat up like that as another drive installed at the same time has higher current harmonics, yet its reactor is not as hot.
Perhaps these reactors are spec'd wrong?
Please advise
RE: Hot line reactor
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RE: Hot line reactor
The drive with higher THID and a cooler running reactor must have a lower impedance reactor. Perhaps it is that one that is wrong. The "hot" reactor seems to be well within its temperature rating. Perhaps all of the others are oversized (lower impedance and higher current rating).
RE: Hot line reactor
Did you mean C, or is it only a 21 C rise on a device rated for a 115 C rise?
RE: Hot line reactor
The reactor is a TCI KDRD24L, 208/240v 15 hp 46.2a with a watt loss of 85. I believe it is 3%, but I do not know the inductance.
RE: Hot line reactor
regarding your post dated July 9th:
If that would be the reason for an reactor to get hot, then what is the difference between an reactor and a resistor ?
RE: Hot line reactor
Now that I re-read it I guess I edited that too many times and ended up oversimplifying it too much. The point I wanted to make was that reactors are never pure inductance, there is always resistance in the circuit so they will always be hot to some extent. In addition, as the reactor doesn't pass higher frequencies, those are converted to heat. So the more harmonics that are present, especially in the higher bandwidths, the hotter the reactor will get.
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Eng-Tips: Help for your job, not for your homework Read FAQ731-376