hde_electric
Member
I have been tryin to explain to a friend why harmonics are not a problem in single phase vs 3 phase but I cannot find a simple way of explaining will somebody give me some imput on this?
single phase vs 3 phase
- Thread starter hde_electric
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Re: single phase vs 3 phase
Single phase is like a one hole outhouse, used by one individual in one time domain.
Three phase is when three individuals use the one holer at a different time domain. When the three use it at the same time, it creates heat, noise, and an odor.
This is like the neutral smoking on a high THD system.
Single phase is like a one hole outhouse, used by one individual in one time domain.
Three phase is when three individuals use the one holer at a different time domain. When the three use it at the same time, it creates heat, noise, and an odor.
This is like the neutral smoking on a high THD system.
hde_electric
Member
Re: single phase vs 3 phase
what is an outhouse?
what is an outhouse?
G
Guest
Guest
Re: single phase vs 3 phase
I have a lot to learn about harmonics but I believe single-phase does have harmonic issues.
Think about switching regulators in computers-- non-linear loads, electronic fluorescent ballasts, and also electronic dimmer switches, etc.
Here is a link to some single-phase harmonic issues:
http://grouper.ieee.org/groups/harmonic/single/docs/
PS: You don't have to upsize the neutral in a single phase-- as you don't have to worry about the harmonics frying the neutral.
[ September 17, 2003, 06:27 PM: Message edited by: awwt ]
I have a lot to learn about harmonics but I believe single-phase does have harmonic issues.
Think about switching regulators in computers-- non-linear loads, electronic fluorescent ballasts, and also electronic dimmer switches, etc.
Here is a link to some single-phase harmonic issues:
http://grouper.ieee.org/groups/harmonic/single/docs/
PS: You don't have to upsize the neutral in a single phase-- as you don't have to worry about the harmonics frying the neutral.
[ September 17, 2003, 06:27 PM: Message edited by: awwt ]
- Location
- Massachusetts
Re: single phase vs 3 phase
I believe it is because single phase is 180 degrees apposed and 3 phase is 120 degrees apposed.
As Bennie said it is a timing thing.
I believe it is because single phase is 180 degrees apposed and 3 phase is 120 degrees apposed.
As Bennie said it is a timing thing.
- Location
- Massachusetts
Re: single phase vs 3 phase
Here you go step on in and do your business.
charlie tuna
Senior Member
- Location
- Florida
Re: single phase vs 3 phase
you can have harmonics in single phase as well as three phase!
you can have harmonics in single phase as well as three phase!
- Location
- Illinois
- Occupation
- retired electrician
Re: single phase vs 3 phase
Harmonics do exist in single pahse systems, but they do not add and overload the grounded conductor like they do on 3 phase systems.
Don
Harmonics do exist in single pahse systems, but they do not add and overload the grounded conductor like they do on 3 phase systems.
Don
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: single phase vs 3 phase
On many of the buildings I inspect they will ask for a 200% nuetral in (at least) one of the panels. What I find interesting is that on the power plan the branch circuits are often multi wire, but the grounded (nuetral) conductor is the same size as the phase conductors. Am I missing something in the logic there?
On many of the buildings I inspect they will ask for a 200% nuetral in (at least) one of the panels. What I find interesting is that on the power plan the branch circuits are often multi wire, but the grounded (nuetral) conductor is the same size as the phase conductors. Am I missing something in the logic there?
karl riley
Senior Member
Re: single phase vs 3 phase
HDE, your friend is right. Harmonics build up on a neutral on three-phase circuits. You need to see a wave-form diagram to understand it, but the most common harmonic, 180Hz, builds up on the neutral from each phase. Thus the neutral can be carrying more current than either of the phases, which means more than it is designed to carry.
Remedy, one neutral per phase, or a larger neutral (you can now purchase these cables).
Karl
HDE, your friend is right. Harmonics build up on a neutral on three-phase circuits. You need to see a wave-form diagram to understand it, but the most common harmonic, 180Hz, builds up on the neutral from each phase. Thus the neutral can be carrying more current than either of the phases, which means more than it is designed to carry.
Remedy, one neutral per phase, or a larger neutral (you can now purchase these cables).
Karl
brian john
Senior Member
- Location
- Leesburg, VA
Re: single phase vs 3 phase
bennie:
Almost fell out of my chair laughing, and with this hurricane coming I need a laugh. We have been running our *** 's off taking care of customers.
Can I borrow your analogy?
bennie:
Almost fell out of my chair laughing, and with this hurricane coming I need a laugh. We have been running our *** 's off taking care of customers.
Can I borrow your analogy?
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