# 3rd, 5th, and higher order Harmonics



## Phatso86 (Sep 9, 2016)

I'm sure this could easily be a conceptual question.

I remember professors specifying that the 3rd harmonic is lower in amplitude than 1st, 5th less than 3rd, 7th less than 5th, etc.  Even in problem statements this was evident by the equation.

BUT this electrical contractor book i'm reading (Mike Holt) says that power dissipated is proportional to the harmonic. This is how they even listed it:

First - I^2

Third - (3xI)^2= 9xI^2

Fifth - (5xI)^2 = 25xI^2 (Book even specifies dangers due to 25x more power dissipation)

There was really no background information on this so I want to know how this occurs or what am I missing from this?


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## Phatso86 (Sep 14, 2016)

Anyone? :huh:


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## Halley_guo (Sep 20, 2016)

I just don't understand your question.

frequency and amplitude are two different concepts.

I don't know why you mixed them up.


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## nukem2k5 (Sep 24, 2016)

I'm no expert on harmonics but I don't think there are any rules of thumb dictating the amplitude of a given harmonic order.  It depends on the attributes of the load in question.


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## Phatso86 (Sep 29, 2016)

Halley_guo said:


> I just don't understand your question.
> 
> frequency and amplitude are two different concepts.
> 
> I don't know why you mixed them up.


thank you for the rude comment, here is mine:

I don't understand why you would post a reply when you have a difficult time comprehending sentences. My post clearly says, " this electrical contractor book i'm reading (Mike Holt) says that power dissipated is proportional to the harmonic." There is no confusion as to what i read. This is evident by the information that followed:

First - I^2

Third - (3xI)^2= 9xI^2

Fifth - (5xI)^2 = 25xI^2 (Book even specifies dangers due to 25x more power dissipation)

if it wasn't clear, the words "first" third" and "fifth"  implied "first harmonic" third harmonic" and "fifth harmonic"


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## Phatso86 (Sep 29, 2016)

nukem2k5 said:


> I'm no expert on harmonics but I don't think there are any rules of thumb dictating the amplitude of a given harmonic order.  It depends on the attributes of the load in question.


yes, i figured it is dependent on the load, i simply do not understand why power dissipation is proportional to harmonics, or when it is.

i'll email the author (he is good a replying) but i doubt i'd get much out of him. He's an electrical contractor, not an engineer.


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## nukem2k5 (Sep 29, 2016)

Harmonics increase the current flowing through the circuit/load, and power = I^2 x R


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## nukem2k5 (Sep 29, 2016)

Oh I see you're asking how the frequency directly amplifies the dissipated power. That's a good question. I'll try to look into it.


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## cupojoe PE PMP (Sep 29, 2016)

Phatso86 said:


> I don't understand why you would post a reply when you have a difficult time comprehending sentences. My post clearly says, " this electrical contractor book i'm reading (Mike Holt) says that power dissipated is proportional to the harmonic." There is no confusion as to what i read. This is evident by the information that followed:


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## matt267 PE (Sep 29, 2016)




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## cupojoe PE PMP (Sep 29, 2016)




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## Halley_guo (Oct 27, 2016)

Phatso86 said:


> thank you for the rude comment, here is mine:
> 
> I don't understand why you would post a reply when you have a difficult time comprehending sentences. My post clearly says, " this electrical contractor book i'm reading (Mike Holt) says that power dissipated is proportional to the harmonic." There is no confusion as to what i read. This is evident by the information that followed:
> 
> ...


Sorry about the former reply. 

I thought it twice. Maybe the author was talking about the power dissipated in the transmission.  In that case, because the current is generated by capacitance paralleling along the transmission line, and the impedance  of the capacitance is invert proportional to the frequency, or Y=jwC I=YU=jwCU   so the lost  would be like this: 

First - I^2

Third - (3xI)^2= 9xI^2

Fifth - (5xI)^2 = 25xI^2 (Book even specifies dangers due to 25x more power dissipation)


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