I attended a conference recently at the National Academy of Sciences in Washington DC, called the Humanitarian Technology Challenge. It was sponsored by the IEEE and the United Nations Foundation, among others. The objective was to organize volunteers from around the world to come up with better ways to apply technology to relieving human suffering.
Even though I am not really a power guy, I found myself engaged in a number conversations about power quality. We were talking about the amount of energy that gets converted to heat from harmonic distortion of the power waveform. Your challenge this month, should you choose to accept it, is to explain why most of the harmonic energy you find on the power mains is in the odd harmonics of the fundamental?
Reply to Butch Shadwell at b.shadwell@ieee.org (email), 904-410-9751 (fax), 904-410-9750 (v), 3308 Queen Palm Dr., Jacksonville, FL 32250-2328. (http://www.shadtechserv.com) The names of correct respondents may be mentioned in the solution column.
Subscribe to:
Post Comments (Atom)
Posts
1 comment:
It seems I am being transformed into a power guy. I hope someone discovers a cure before it is too late. Your challenge this month, should you choose to accept it, is to explain why most of the harmonic energy you find on the power mains is in the odd harmonics of the fundamental?
Derek Paice sent me a very nice answer to this BTC, so I am going to give you his response "Rotating machines are generally symmetrical in the sense that negative half cycles have a similar shape wave to that of the positive half cycles. Mathematically f(wt + pi) = - f(wt).
In a Fourier analysis of a total waveform like this, expressions for individual harmonics of number n include a multiplier of sin (n x pi/2). If n is an even number this expression becomes zero, hence there are few even harmonics from generators.
Individual loads can draw even harmonics, but IEEE Std 519 guideline discourages use of loads causing even harmonics of current, by limiting their tolerable amount to 25% of the allowable odd harmonics." But I bet you already knew that.
Post a Comment