hde_electric
Member
Why is it that harmonic currents are not such a big problem with Single phase and they are on three phase? What happens if you have someone with 5 computers and non-linear loads in a residence will this be a problem?
Harmonic Currents In Single Phase
- Thread starter hde_electric
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karl riley
Senior Member
Re: Harmonic Currents In Single Phase
In single phase the neutral will not be carrying any more current than the hot.
In three phase with one neutral, the harmonics build up on the neutral due to the fact that 180Hz, etc does not cancel between the phases, so the neutral can be carrying more current than any of the phases. One remedy is using 3 neutrals, so that it is like 3 single-phase circuits. The other remedy is a larger neutral.
To prevent harmonics check with Dereck!
Karl
In single phase the neutral will not be carrying any more current than the hot.
In three phase with one neutral, the harmonics build up on the neutral due to the fact that 180Hz, etc does not cancel between the phases, so the neutral can be carrying more current than any of the phases. One remedy is using 3 neutrals, so that it is like 3 single-phase circuits. The other remedy is a larger neutral.
To prevent harmonics check with Dereck!
Karl
brian john
Senior Member
- Location
- Leesburg, VA
Re: Harmonic Currents In Single Phase
Durn I love the internet:
(and all of you harmonic causing end users)
HDE check this out
http://www.copper.org/pq/issues.html
Durn I love the internet:
(and all of you harmonic causing end users)
HDE check this out
http://www.copper.org/pq/issues.html
karl riley
Senior Member
Re: Harmonic Currents In Single Phase
Thanks Brian, great source. Tells it all.
Karl
Thanks Brian, great source. Tells it all.
Karl
Re: Harmonic Currents In Single Phase
I read the white paper and found it informative. However I found thier reccomended solutions a little biased, which they alluded too. All the solutions were copper based, which is what you would expect from the copper industry. What they did not mention was the most effective means such as MG and dual conversion UPS. Just some food for thought.
- Location
- Illinois
- Occupation
- retired electrician
Re: Harmonic Currents In Single Phase
dereck,
They also never talk about the use of true single phase distribution to prevent excessive current on the neutral with nonlinear loads.
don
dereck,
They also never talk about the use of true single phase distribution to prevent excessive current on the neutral with nonlinear loads.
don
brian john
Senior Member
- Location
- Leesburg, VA
Re: Harmonic Currents In Single Phase
hde A good book for your library.
http://web.idirect.com/~a1parts/mw_handbook.html
hde A good book for your library.
http://web.idirect.com/~a1parts/mw_handbook.html
scott thompson
Senior Member
- Location
- Anaheim, California
Re: Harmonic Currents In Single Phase
Just wanted to add a little to the previously made informative posts.
Yes, there will still be Harmonic Currents involved with a 1? System, but the effects on the Common Grounded (Neutral) Conductor of Multiwire Circuits aren't like those of Polyphase Multiwire Circuits (3? 4 Wire Wye Systems).
The level of Distortion needs to be considered. 10% THD would include an additional 10% Line Current on the 2 Wire Circuit. 20% THD adds 20% more, and 33% adds 33% more.
On 3? 4 Wire Wye Systems using 4 Wire Multiwire Branch Circuits for Loads having ? 30% THD, the Common Grounded Conductor will be carrying upto (or possibly more than) 200% of the Load Current.
I have given some very basic, simple descriptions here, but they cover the topic enough to give you more ideas of what to look for in studies.
Scott
p.s. - it's been Eons since my last post in this forum! How are all of you?
Scott35
Just wanted to add a little to the previously made informative posts.
Yes, there will still be Harmonic Currents involved with a 1? System, but the effects on the Common Grounded (Neutral) Conductor of Multiwire Circuits aren't like those of Polyphase Multiwire Circuits (3? 4 Wire Wye Systems).
The level of Distortion needs to be considered. 10% THD would include an additional 10% Line Current on the 2 Wire Circuit. 20% THD adds 20% more, and 33% adds 33% more.
On 3? 4 Wire Wye Systems using 4 Wire Multiwire Branch Circuits for Loads having ? 30% THD, the Common Grounded Conductor will be carrying upto (or possibly more than) 200% of the Load Current.
I have given some very basic, simple descriptions here, but they cover the topic enough to give you more ideas of what to look for in studies.
Scott
p.s. - it's been Eons since my last post in this forum! How are all of you?
Scott35
pierre
Senior Member
- Location
- Westchester County, New York
Re: Harmonic Currents In Single Phase
Hey Scott
Hope the reason for not hearing from you was you had a busy and fun summer!
Its good to hear from you.
Pierre
Hey Scott
Hope the reason for not hearing from you was you had a busy and fun summer!
Its good to hear from you.
Pierre
scott thompson
Senior Member
- Location
- Anaheim, California
Re: Harmonic Currents In Single Phase
Thanks to both of you for the warm welcome back!
Roger, The Shop / Office of the new Company I'm working with is located right next to the BNSF's very busy San Bernardino Subdivision (was the ATSF 3rd District), just ? mile from Fullerton Depot.
The Junction to Metrolink's San Diego Subdivision (was the ATSF 4th District) is about 100 yards away, so there's a bunch of Passenger traffic also.
I would say that on an average day (between 6:30 AM and 5:00 PM), at least 15 Freight Trains pass by, the Local Switcher passes by twice, around 10 Amtrak "locals" + the Southwest Limited pass by, and something like 8 Metrolink locals pass by.
Since I have been spending most of the time at the Shop / Office, get to see all kinds of runs!
The Block Signals which protect the Junction (and signal for diverging over crossovers) are right behind our yard. Lots of Freights get held at this Block, to keep back for the Commuter Traffic at the Depot, and the high volume of Traffic occupying the Blocks ahead.
Almost all the Locomotives used by BNSF in this territory are C44-9Ws (made by General Electric). Sometimes a few legacy units will be lashed up with Dash 9's (like SD 40-2s, GP 38-2s and such). Along with those, there might be the few odd SD-60Ms, SD-75s and GP-60Ms, which are not legacy units. ("GP"s and "SD"s are made by General Motors / EMD).
All the Metrolink runs use the common B39-8MW units (made by GE), and the Amtrak locals use the common F59PHI (made by GM/EMD). The Southwest uses a 5 unit lash up of P40-8's / P42-8s (made by GE).
There was an exec. Passenger Train one day (on the San Bernardino Subdivision to boot!), which was using an old legacy F40PH unit! (made by GM/EMD).
You could easilly identify it from the signature sound of high idle at stop.
The Train was at the Absolute Block Signal waiting for clearance, and the whole time the prime mover of the F40 was at high speed. (high speed is 900 RPMs max., but being that the prime mover is a 2 stroke 16 cylinder Motor, it sounds like the speed is more like 10,000 RPMs!).
OK, I'll stop boring everyone with this Train junk!!!
Pierre;
If only it was true, that the last 6 or so Months was a nice Vacation! (well, at least having the ex 3rd District only 50 feet away makes things much nicer!). Instead, its been an non-stop Estimation, Design / Engineer and Management fury!
Now everything has come to a screetching halt!
Scott35
Thanks to both of you for the warm welcome back!
Roger, The Shop / Office of the new Company I'm working with is located right next to the BNSF's very busy San Bernardino Subdivision (was the ATSF 3rd District), just ? mile from Fullerton Depot.
The Junction to Metrolink's San Diego Subdivision (was the ATSF 4th District) is about 100 yards away, so there's a bunch of Passenger traffic also.
I would say that on an average day (between 6:30 AM and 5:00 PM), at least 15 Freight Trains pass by, the Local Switcher passes by twice, around 10 Amtrak "locals" + the Southwest Limited pass by, and something like 8 Metrolink locals pass by.
Since I have been spending most of the time at the Shop / Office, get to see all kinds of runs!
The Block Signals which protect the Junction (and signal for diverging over crossovers) are right behind our yard. Lots of Freights get held at this Block, to keep back for the Commuter Traffic at the Depot, and the high volume of Traffic occupying the Blocks ahead.
Almost all the Locomotives used by BNSF in this territory are C44-9Ws (made by General Electric). Sometimes a few legacy units will be lashed up with Dash 9's (like SD 40-2s, GP 38-2s and such). Along with those, there might be the few odd SD-60Ms, SD-75s and GP-60Ms, which are not legacy units. ("GP"s and "SD"s are made by General Motors / EMD).
All the Metrolink runs use the common B39-8MW units (made by GE), and the Amtrak locals use the common F59PHI (made by GM/EMD). The Southwest uses a 5 unit lash up of P40-8's / P42-8s (made by GE).
There was an exec. Passenger Train one day (on the San Bernardino Subdivision to boot!), which was using an old legacy F40PH unit! (made by GM/EMD).
You could easilly identify it from the signature sound of high idle at stop.
The Train was at the Absolute Block Signal waiting for clearance, and the whole time the prime mover of the F40 was at high speed. (high speed is 900 RPMs max., but being that the prime mover is a 2 stroke 16 cylinder Motor, it sounds like the speed is more like 10,000 RPMs!).
OK, I'll stop boring everyone with this Train junk!!!
Pierre;
If only it was true, that the last 6 or so Months was a nice Vacation! (well, at least having the ex 3rd District only 50 feet away makes things much nicer!). Instead, its been an non-stop Estimation, Design / Engineer and Management fury!
Now everything has come to a screetching halt!
Scott35
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