![]() ![]() Some even allow entry of cost/kWh to obtain total cost. ![]() Or you can purchase dedicated power analyzers that display RMS voltage, current, power, power factor, phase angle, and total (and peak) watt-hours. You can just purchase one of the many three phase wattmeter and power analyzer ICs and add the required external PTs and CTs, and interface it to a microcontroller to log and display the values. Given the current and voltage of a consumer electronic device, how to calculate its power draw?.What's the most economical way to digitally measure 240V mains voltage, current and power factor?.Is Induction Wattmeter ,Energy Meter and Watt Hour Meter the same thing.How is the power factor part involved in wattmeter reading?.Use this method in the equivalent of a two or three wattmeter method. Then you accumulate the \$v \times i\$ sampled value over (say for instance) 1 second and divide by the samples per second. If you sample and multiply at a higher rate then even better. Going back to \$v \times i\$, you can employ modern digital techniques and sample at around 20 times the line frequency as a minimum to avoid current waveform harmonics contributing too much of an error. Sure there are 3-phase heating elements and these'll be OK but, in the main, you'll be disappointed with V.I.Cos(φ).īut, if your supply is both amplitude and phase balanced and feeds a linear load then you can use that method. It's folly to think you might be able to do this for practical loads except a kettle and, I don't think they make three phase kettles. In other words, your formula assumes a balanced and linear load with a voltage source that is balanced both in amplitude and 120° phase angles. not wholly resistive) therefore, using zero-crossing detectors (for example) for estimating phase angle, is a bit useless and, gives rise to significant errors. If you try and calculate power using power factor then you have to measure phase angle between \$v\$ and \$i\$ and, the massive problem with this, is that a typical load may be somewhat non-linear (i.e. In other words, it's \$v \times i\$ with no worries about power factor. Image from Measurement of Three Phase Power: Three Wattmeter Method and, again I'm showing old fashioned wattmeter methods because, if you want accuracy despite non-linear loads or asymmetrical voltage supplies you have to look at what a wattmeter does.Ī wattmeter is an analogue multiplier of the voltage and current waveforms. There is also the three wattmeter method:. Image from Two Wattmeter Method of Power Measurement and, I mention this because, it is a true 3-phase measurement of power into a 3-phase load. The simplest way is probably this the two wattmeter method:. ![]()
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