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Content of rectified sine
Looking at the content of a rectified sine wave, this is
what I get, where F1 is twice mains frequency, and values are harmonics of F1 as proportions of rms source V: Mean voltage Vdc: 0.9 - diode drops Ripple Vrms: F1: 0.424 2H: 0.085 4H: 0.032 6H: 0.016 8H: 0.0086 10H: 0.0045 Leaving around 0.014 unaccounted for, widely and comparatively evenly spread over the next 30 or so even harmonics. Note that AFAICS those first few harmonics are not significantly changed by diode drop as long as it's less than about 15% of transformer secondary voltage. The higher harmonics are reduced. All frequencies lead the mains sine by 90 degrees, such that when the rectified sine is at zero, the fundamental and all harmonics are at their peak negative values, which should sum with the mean voltage to give zero. Currents and voltages at any point in a power supply circuit can be calculated by analysing for each frequency and combining the results. The algebraic formula for a generalised circuit is a bit long but once done, a spreadsheet can be constructed so different component values can be tried easily. Here's a reminder of how to deal with vectors: http://www.kwantlen.ca/science/physi...s/Phasors.html Don't forget the effective series resistance of the transformer, which can be estimated from its rated current and regulation. Ian |
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