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Shop made line reactor
- Thread starter CalG
- Start date
- Replies 35
- Views 14,751
The real Leigh
Diamond
- Joined
- Nov 23, 2005
- Location
- Maryland
Hi Cal,
I just researched this with the intention of doing the same thing.
I found a two-page paper from Allen-Bradley entitled "Line reactors and AC drives" that gives a good discussion
http://www.ab.com/drives/techpapers/Line Reactors and AC Drives1.pdf
Line reactors can be used for several different purposes:
1) To protect other equipment connected to the AC supply from noise and harmonics generated by the drive;
2) To protect the drive from noise and transients on the AC supply line;
3) To protect the drive from damage due to high inrush current at turn-on.
The "filtering" that you mentioned may be incorporated in commercial reactors to enhance the performace in case #1 by attenuating high-frequency harmonics more effectively.
A line reactor is just an inductor, and of relatively small value.
For single-phase power you only need one. For three-phase you need one on each phase (commercial products have all three in one housing).
Peter was kind enough to clarify the terminology for me.
Line reactors are defined in terms of "percent", meaning a percentage of the load impedance, with typical values of 2% to 5%.
You can calculate the various parameters and come up with an accurate value for the reactor impedance, but since that number will vary with motor loading, it's hardly worth the effort.
The impedance I got for a 5 hp motor on single-phase 220v power was 5.5 ohms. A 3% reactor would have an impedance of 0.165 ohms and an inductance of 0.438 millihenries.
Peter suggested five turns of the wire that feeds the motor wound on a piece of iron pipe. That's probably close enough for our purposes.
- Leigh
I just researched this with the intention of doing the same thing.
I found a two-page paper from Allen-Bradley entitled "Line reactors and AC drives" that gives a good discussion
http://www.ab.com/drives/techpapers/Line Reactors and AC Drives1.pdf
Line reactors can be used for several different purposes:
1) To protect other equipment connected to the AC supply from noise and harmonics generated by the drive;
2) To protect the drive from noise and transients on the AC supply line;
3) To protect the drive from damage due to high inrush current at turn-on.
The "filtering" that you mentioned may be incorporated in commercial reactors to enhance the performace in case #1 by attenuating high-frequency harmonics more effectively.
A line reactor is just an inductor, and of relatively small value.
For single-phase power you only need one. For three-phase you need one on each phase (commercial products have all three in one housing).
Peter was kind enough to clarify the terminology for me.
Line reactors are defined in terms of "percent", meaning a percentage of the load impedance, with typical values of 2% to 5%.
You can calculate the various parameters and come up with an accurate value for the reactor impedance, but since that number will vary with motor loading, it's hardly worth the effort.
The impedance I got for a 5 hp motor on single-phase 220v power was 5.5 ohms. A 3% reactor would have an impedance of 0.165 ohms and an inductance of 0.438 millihenries.
Peter suggested five turns of the wire that feeds the motor wound on a piece of iron pipe. That's probably close enough for our purposes.
- Leigh
Iron pipe or DOM steel ? ;-))
Perhaps an iron window sash weight would be ideal?
this is just like a "stabilizer" for an arc welder. (does anyone remember the publication by entitled "the Stabilizer" ?)
A box above the box would do it. We need a topic in the sticky "show us your line reactors"
Cal
Cal
Perhaps an iron window sash weight would be ideal?
this is just like a "stabilizer" for an arc welder. (does anyone remember the publication by entitled "the Stabilizer" ?)
A box above the box would do it. We need a topic in the sticky "show us your line reactors"
Cal
Cal
The real Leigh
Diamond
- Joined
- Nov 23, 2005
- Location
- Maryland
The sash weight might work, although they're a bit difficult to find these days. 
Any ferrous material would work. For the low value of inductance under discussion the thing would not be very large.
I'll probably use a toroid if I can find a suitable one. Much more stable inductance value, and not susceptible to the surrounding environment.
Amidon shows 46 turns of #9 AWG wire on a T-400A powdered iron core of #26 material as 800 microhenries, good for 30 amps. Upsizing to #8 AWG with slightly fewer turns should work fine. This core is 4" OD.
- Leigh
Any ferrous material would work. For the low value of inductance under discussion the thing would not be very large.
I'll probably use a toroid if I can find a suitable one. Much more stable inductance value, and not susceptible to the surrounding environment.
Amidon shows 46 turns of #9 AWG wire on a T-400A powdered iron core of #26 material as 800 microhenries, good for 30 amps. Upsizing to #8 AWG with slightly fewer turns should work fine. This core is 4" OD.
- Leigh
Rody
Aluminum
- Joined
- Aug 7, 2007
- Location
- North Vancouver
Line reactors cost about 150 and are available from any motor drive supplier. Well worth the money.
Chip Chester
Diamond
- Joined
- Dec 13, 2007
- Location
- Central Ohio USA
Sash weights! Get your sash weights here! Free sash weights!
Just pay our low shipping and handling fee, and they're yours!
Seriously, I've got about 50 of 'em so far, from a whole-house window replacement project. So far, I've used a few for ballast on various projects, but it looks like I could go into the 'reactor' business!
Chip
Central Ohio, if you'd like a few...
Just pay our low shipping and handling fee, and they're yours!
Seriously, I've got about 50 of 'em so far, from a whole-house window replacement project. So far, I've used a few for ballast on various projects, but it looks like I could go into the 'reactor' business!
Chip
Central Ohio, if you'd like a few...
peterh5322
Diamond
- Joined
- Dec 15, 2002
- Location
- Monterey Bay, California
"A short (50mm) section of CI vent pipe and a few turns of supply wire"
A piece of 2" conduit or "no hub" C.I. pipe with the feeder conductor threaded through the pipe several times should be good enough.
I'd apply something to protect the conductor from the (possibly) sharp ends of the pipe.
What you're constructing, using "found" materials, is a low-resistance, low-inductance choke.
A factory manufactured choke could be (probably would be) higher performance, but what we're looking for here is a "lossy" element which can absorb unwanted transients, and perhaps a low-performance solution is actually better than a higher performance one.
The low-performance solution certainly would be more economical.
A piece of 2" conduit or "no hub" C.I. pipe with the feeder conductor threaded through the pipe several times should be good enough.
I'd apply something to protect the conductor from the (possibly) sharp ends of the pipe.
What you're constructing, using "found" materials, is a low-resistance, low-inductance choke.
A factory manufactured choke could be (probably would be) higher performance, but what we're looking for here is a "lossy" element which can absorb unwanted transients, and perhaps a low-performance solution is actually better than a higher performance one.
The low-performance solution certainly would be more economical.
DaveKamp
Titanium
- Joined
- Oct 3, 2004
- Location
- LeClaire, Ia
I'm with Chip...
Ann and I just did a whole-house window replacement on our 1919 four-square, and just so happens that this morning, the ground was solid enough for me to drive the Cub Cadet and heavy garden trailer around... I picked up 68 weights from the ground...
And it's obvious by looking at 'em... that they possess a characteristic best described as 'variable-permiability'...
But I'm sure they're good for a few uH...
Ann and I just did a whole-house window replacement on our 1919 four-square, and just so happens that this morning, the ground was solid enough for me to drive the Cub Cadet and heavy garden trailer around... I picked up 68 weights from the ground...
And it's obvious by looking at 'em... that they possess a characteristic best described as 'variable-permiability'...
But I'm sure they're good for a few uH...
DaveKamp
Titanium
- Joined
- Oct 3, 2004
- Location
- LeClaire, Ia
Lossy?
Now... if you use a piece of old cast-iron pipe, and the pipe was rusted through and leaking in a few places... does that make it more 'lossy'?
(yes, that's a joke...)
Now... if you use a piece of old cast-iron pipe, and the pipe was rusted through and leaking in a few places... does that make it more 'lossy'?
(yes, that's a joke...)
Toms Wheels
Titanium
- Joined
- Dec 30, 2005
- Location
- Jersey Shore
For $52 I purchased a brand new 30amp 3 phase GE reactor on ebay. 18# of iron and copper. No buzz at all when in use. It was wound with square wire guessing 8awg.
Low-Alloy
Aluminum
- Joined
- Oct 9, 2004
- Location
- Pacific NW (U.S.A.)
Leigh, have you moved forward with a D.I.Y. line reactor? For such a simple devise (I know nothing about them other wire rapped around a ferrous core
) they seem awfully expensive! Can you give a ballpark D.I.Y. design that would satisfy the needs for de-rating VFD's-- 5hp motor/10hp VFD, that sort of thing?
Line filter
After starting this topic, a small capacity AB 3ph unit showed up on Ebay
The price was OK, thinking the innards could be "back engineered.
What do you suppose? The entire thing is cased in metal and potted in Epoxy! Drat!
Well It is a perfctly good 2HP line filter desigend for variable frequency drives (AB 160 line filter)
While doing a bit of web research on the unit, It caught my attention that this device carries differing part numbers for differing voltage applications when built to "Class A", but one part number covers both 200-240 and 380-460 Volt applications under the combination class A&B designation.
Could someone shed light on these class designations and perhaps a stab at the differences referenced?
Attached are three circuit schemes of increasing sophistication and complexity for a conversation starter.
CalG
After starting this topic, a small capacity AB 3ph unit showed up on Ebay
The price was OK, thinking the innards could be "back engineered.
What do you suppose? The entire thing is cased in metal and potted in Epoxy! Drat!
Well It is a perfctly good 2HP line filter desigend for variable frequency drives (AB 160 line filter)
While doing a bit of web research on the unit, It caught my attention that this device carries differing part numbers for differing voltage applications when built to "Class A", but one part number covers both 200-240 and 380-460 Volt applications under the combination class A&B designation.
Could someone shed light on these class designations and perhaps a stab at the differences referenced?
Attached are three circuit schemes of increasing sophistication and complexity for a conversation starter.
CalG
Forrest Addy
Diamond
- Joined
- Dec 20, 2000
- Location
- Bremerton WA USA
Adding my 2 cents.
I made lots of quick and dirty line reaactors back in the day. I used a few turns of the line conductor passed through the eye of a suitable pipe. They worked OK for the most part.
Iron pipe seemed to work the best at snubbing transients and actual E/I cores salvaged from old transformers the worst. My thinking is the "lossier" - that is the poorer - magnetic properties of junkyard steel blots up more transient energy than a high quality transformer iron. I never used cast iron pipe but I wonder if it might even be better
I made lots of quick and dirty line reaactors back in the day. I used a few turns of the line conductor passed through the eye of a suitable pipe. They worked OK for the most part.
Iron pipe seemed to work the best at snubbing transients and actual E/I cores salvaged from old transformers the worst. My thinking is the "lossier" - that is the poorer - magnetic properties of junkyard steel blots up more transient energy than a high quality transformer iron. I never used cast iron pipe but I wonder if it might even be better
Line filter ideas
This information for a large DC drive.
It is interesting that the page shows an R/C device rather than an L/C system
http://www.rockwellautomation.com/relianceelectricdrives/get/d23424.pdf
Cal
Edit: This page shows a table of turns around a torroid suitable for different ampacities etc.
http://www.bytemark.com/products/acapp.htm
This information for a large DC drive.
It is interesting that the page shows an R/C device rather than an L/C system
http://www.rockwellautomation.com/relianceelectricdrives/get/d23424.pdf
Cal
Edit: This page shows a table of turns around a torroid suitable for different ampacities etc.
http://www.bytemark.com/products/acapp.htm
Last edited:
The real Leigh
Diamond
- Joined
- Nov 23, 2005
- Location
- Maryland
Hi Cal,
There are two accessories available for the power input to a VFD, and they serve very different functions.
The AC Line Filter kit is designed to attenuate high-frequency transients coupled from the transformer primary into the lines feeding the VFD. This is an appropriate application for an R/C snubber. It's connected from the supply lines to ground and does not conduct load current.
The Line Reactor is quite different. It's an inductor, usually on a metal core, with a single winding connected in series with the power line going into the VFD. Thus it must handle full load current. (Three-phase reactors have three separate inductors, one in each wire.)
The purpose of the Line Reactor is to limit inrush current to the VFD. When you turn on any piece of electrical equipment, it presents a short circuit to the power lines until the power supply capacitors charge. This short circuit causes very high current to flow in the primary wiring.
An inductor, by definition, opposes any change in current flow. So when the short-circuit current tries to increase from zero, the inductor opposes that change and limits its magnitude.
Here's a photo of a line reactor I'm using on the 5 hp lathe. It's seven turns of #6 wire on a homemade toroid built from 3/4" iron pipe.
n.b. When characterizing coils, the number of turns only includes complete turns. Partial turns are irrelevant.
- Leigh
Low-Alloy
Aluminum
- Joined
- Oct 9, 2004
- Location
- Pacific NW (U.S.A.)
That is exactly what I was looking for! Thanks The Real Leigh! 
It's hard to Know
The device (AB 160) has the description "Line Filter", but the wiring scheme shows input L1, L2, and L3, along with outputs to the VFD as T1, T2, and T3. (series wired) One would think the load power might pass through the device, but it does not have to be.
If I have time tomorrow, I'll hook it up to the signal generator along with the dual trace scope on the "in and out" and see if there is any knowledge to be gained.
Does your "plumbers puzzle" need to close the circle in order to function as an inductor? I was thinking all three lines (or two as the case may be) wraped around a straight section of pipe might be the trick. No moving parts either ;-))
CalG
Edit
PS I'm gonna throw the amp clamp on the feed lines to the VFD as well. During "bench testing" I could not detect ANY inrush related indications. The VFD initiates at zero frequency (well 6 hz on one machine, I need to re-program that drive!)
The device (AB 160) has the description "Line Filter", but the wiring scheme shows input L1, L2, and L3, along with outputs to the VFD as T1, T2, and T3. (series wired) One would think the load power might pass through the device, but it does not have to be.
If I have time tomorrow, I'll hook it up to the signal generator along with the dual trace scope on the "in and out" and see if there is any knowledge to be gained.
Does your "plumbers puzzle" need to close the circle in order to function as an inductor? I was thinking all three lines (or two as the case may be) wraped around a straight section of pipe might be the trick. No moving parts either ;-))
CalG
Edit
PS I'm gonna throw the amp clamp on the feed lines to the VFD as well. During "bench testing" I could not detect ANY inrush related indications. The VFD initiates at zero frequency (well 6 hz on one machine, I need to re-program that drive!)
The real Leigh
Diamond
- Joined
- Nov 23, 2005
- Location
- Maryland
Line filters are generally between the AC supply and the VFD, either in series or in shunt to ground, depending on the intended function. While it's possible to put a similar device between the VFD and the motor, these are used for very different reasons and in special situations, not related to the current discussion.
A device with a closed magnetic path (i.e. a toroid) will exhibit significantly greater inductance for a particular pipe size and number of turns than a simple straight pipe. You'll have an inductor in either case. All plumbing components must be iron, not copper or brass.
I would not recommend wrapping multiple lines on a common core. When you do so you create a transformer, just like power transformers in power supplies. The effects would be unknown since the phasing and coupling are not fully characterized. Not a good idea. Commercial line reactors have a separate inductor for each line.
You won't see any transients with a clamp-on ammeter.
You need a high-frequency storage scope. Line transients of this type last less than 5 milliseconds, and frequently less than 1 ms.
A 'scope with built-in "glitch" detection is ideal, because you don't have to fiddle with the triggering.
And realize that inrush current can vary by several orders of magnitude from one turn-on event to the next. It all depends on the exact point on the voltage waveform when the switch contacts close.
- Leigh
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