tag:blogger.com,1999:blog-6161778274523938171.post3801820654966525145..comments2023-06-23T04:41:12.261-04:00Comments on Watt's Up?: Measurement of AC plus DC voltageGaryRhttp://www.blogger.com/profile/13342106993487479289noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-6161778274523938171.post-15883666684537520192014-11-19T19:59:44.814-05:002014-11-19T19:59:44.814-05:00Hello John,
Thank you for your questions! The fir...Hello John,<br /><br />Thank you for your questions! The first calculation in your first paragraph is exactly correct: the peak of 100 Vac + 50 Vdc is 191.42 V and agrees with the plot. As for the voltage at time = 0, the sine wave is not synchronized with the time scale shown. So for this example, the sine wave zero crossing does not occur at time = 0. If the sine wave crossed zero volts at time = 0, your observation that the voltage should be 50 V at time = 0 would be correct. In this example, the sine wave is shifted about 0.4 ms to the left, so the voltage at time = 0 is higher contributing to the higher observed voltage [141.42 x sin (2*pi*60*0.0004) + 50 = 71.2 V which is roughly the observed voltage at time = 0].<br /><br />As for the capabilities of these AC sources, yes, the output can produce 300 Vrms or +/-425 Vdc. The 111.80 V is not the input voltage of this AC source; it is the output. Discussing these AC sources can be confusing because they have an AC input and an AC output. In this case, the 111.80 V is the programmed output voltage as a combination of AC + DC settings. For the AC input, these AC sources can be plugged into a standard AC line and the source converts the AC line voltage into a high voltage DC rail, and then uses power electronics (a sophisticated inverter circuit) to reconvert the DC into the well-regulated AC (+DC) output. So I was running this AC source from a standard 120 Vac, 60 Hz outlet and I programmed its output to 100 Vac and 50 Vdc. I could set any AC output voltage between 0 and 300 Vac, and any DC output voltage between -425 and +425 Vdc, and the AC source will regulate its output at this setting (as long as the peaks do not exceed the capabilities). The 6812B AC source I used can be purchased with one of several AC input voltage options to allow it to work from any standard single-phase AC input line in the world (100 Vac, 120 Vac, 200 Vac, 208 Vac, or 230 Vac).<br />GaryRhttps://www.blogger.com/profile/13342106993487479289noreply@blogger.comtag:blogger.com,1999:blog-6161778274523938171.post-5746365659920796542014-11-19T02:10:57.107-05:002014-11-19T02:10:57.107-05:00In the figure with +offset, I can understand a pos...In the figure with +offset, I can understand a positive peak voltage close to 200V, which is [100 * SQRT(2) + 50]V = 191.42. But why at time 0 when the AC is at 0V, the total voltage display is about 70V (50 * 1.414) instead of the 50V DC component.<br /><br />You mentioned that " These AC sources can produce output voltages of up to 300 Vrms and DC voltages up to +/- 425 Vdc." Can you explain how can an input voltage of Vrms = 111.80V produce an output voltage higher than the input? ThanksAnonymoushttps://www.blogger.com/profile/04773354630075470145noreply@blogger.com