# Understanding the fundamental component of a wave

Discussion in 'Electronics Homework Help' started by JonnyDriller, Apr 15, 2020.

1. ### JonnyDriller

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0
Apr 6, 2020
We were supposed to design these circuits in Matlab but the plague happened so. I'm trying to work backwards here to understanding something. See this figure here, can someone explain to me how the fundamental can be 89.99?
I'm assuming this is percent, but percent of what? Relative to what?
I'm also assuming that the fundamental is 20.33% of the overall frequencies at work in the wave.
So whats the story with Mr. 89.99?

2. ### duke37

5,364
772
Jan 9, 2011
It looks to me to be a 1200Hz carrier which is FM modulated with 50Hz. At a certain level of modulation, The carrier disappears..
The harmonics of the 50Hz are 1,2,4,5,

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3. ### JonnyDriller

9
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Apr 6, 2020
And you got all that from that chart? You're a better man than me.
How can you see the harmonics numbers? 1 obviously is the fundamental.

edit sorry ok the carrier disappears @duke37
2 would be 100Hz right? but there's nothing there either.
Now obviously you can tell I'm a harmonics beginner, I'm starting to grasp the concepts but only barely.

The thing is one phase of a 3 phase PWM circuit. This is the signal output

Last edited: Apr 16, 2020
4. ### JonnyDriller

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Apr 6, 2020
You know what @duke37. I think you're right about the 1200HZ value, it states the carrier is 24 times the base.

5. ### duke37

5,364
772
Jan 9, 2011
There is a line 50Hz below 1200Hz and another 50Hz above 1200Hz and so ad infinitum.
I think the modulation only has odd harmonics but I could be wrong.

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6. ### JonnyDriller

9
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Apr 6, 2020
I've read through it a few times can't see anything about odd harmonics. Whats the 89.99 thing @duke37.
The setting in this say Max frequency is 2000 Hz and the period is 0.02. I keep seeing people multiplying these.
So is Mr 89.99 the percentage of the product of that? Hmmm?

7. ### JonnyDriller

9
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Apr 6, 2020
Right... right right I get it now. Cheers dudes, please consider the topic closed. Thx duke