AC vs DC voltage Part 1: RMS Equivalent heating value explained
188This is the first video of a three part series, where the root-mean-square (RMS) average value of the AC voltage is explained and compared to DC voltage. When it comes to the 110V AC or 230V AC line voltage, people have the tendency to think that from the wall socket they receive a fixed 110V or 230V voltage. In contrast to this popular believe, the line voltage fluctuates between 0V and a peak voltage according to the shape of a sine wave. The peak voltage is SQRT2 (~1.414) times larger than the nominal AC line voltage. Therefore, in the case of 110V AC the peak voltage coming from the wall socket into a power supply is 155V, wheres in the case of 230V AC the peak voltage is 325V. This has a ramification that the voltage on the filter capacitor will be also SQRT2 (~1.414) times larger than the nominal AC voltage fed into the circuit.
Due to the sinusoidal oscillating voltage, also the current flowing through the circuit will fluctuate accordingly. Thus, it is not straightforward to express the amount of power delivered to a load by an AC power supply. To make the conversion between AC and DC power sources more simple, in electronics and in electric engineering we use the so called equivalent heating value. This means, that a 230V AC sinusoidal power source will produce the equivalent amount of heat on a purely resistive load like a 230V DC power source. Of course, when we look at the shape of the 230V AC sinusoidal voltage, it is not 230V DC, but instead constantly fluctuates between 0V base value, +325V and -325V peak values with a frequency of 50Hz. For comparison, in the US the 110V AC line voltage will fluctuate with a frequency of 60Hz between 0V and the +155V and -155V peak values.
In the following part we will look at the way how the RMS value is being calculated by using Python via Jupyter and doing some very basic mathematics. This way the viewers will become familiar with the method of how RMS is being mathematically evaluated on a sinusoidal function like an AC line input voltage.