Calculating Active, Reactive & Apparent Power from Voltage & Current on Transformer (1ms Sampling)

Hello

I am an electronics novice with a question. It measures the voltage and current on the transformer with 1ms sampling. Can the powers given in the topic be calculated from these measurements? I do not know how to determine the fi angle, as long as it can be determined from these measurements.

I don't quite know how to interpret it. Is it that you connect the transformer to some source and measure the voltage and current on the primary winding when idling? The circuit will be inductive. The power dissipated in such a system will be very small.

You measure voltage and current with some device that samples these values every 1ms. You can measure the offset angle between voltage and current (at least approximately) with this.
You will calculate the apparent power (S) on the basis of the rms values of voltage and current.
S = U * J

You will calculate the reactive power (in this system it will have a positive value) from the product of RMS voltage and current and the sine of the phase shift angle.
Q = U * J * sin (? ;)

And the active power is the same as the reactive power, only the cosine of the angle.
P = U * J * cos (? ;)

I don't really understand why such a calculation is. Is it some assignment for school?

That's exactly the job. Only that I do not have a device for measuring this fi angle. I only have to measure voltage and current with 1ms sampling. Is it possible to determine the angle fi on this basis?

Well, the shift can be determined with this device with a certain accuracy.
By measuring voltage and current at intervals of one millisecond and marking the values on the graph, current and voltage waveforms will be generated. Now, from the graph, we can read how many degrees the voltage is ahead of the current (it is an inductive system, so the voltage is ahead of the current). In the ideal coil, the voltage is ahead of the current by an angle of 90 °.

Hello and welcome,

assuming the meter measures the instantaneous value of current and voltage, we have
u = Umsin (?t + ?u) ii = Imsin (?t + ?i), because ? = ?u-?i is the phase shift angle between voltage and current, hence for a moment (sample) e.g. t1 = 3ms you are able to determine the value of this angle.
The instantaneous power can be determined by:
p = u * i = Um * sin?t * Im * sin (?t-? = (Um * Im) / 2 [cos?-cos (2?-? ] =
= U * I [cos?-cos (2?-? ] = U * Icos?-U * Icos (2?t-? .

U * Icos?- is a constant component
U * Icos (2?t-? - sinusoidal variable component

Regards
Stephen

As for the coil, I can write so much
The voltage on the coil is 90 degrees ahead of the current, so yes.
1. Phase shift angle ?
? = ?u - ?i = 90 ° - 0 ° = 90 °

2.Active power
P = U * I * cos? = U * I * 90 ° = U * I * 0 = 0
cos?- power factor
cos90 ° = 0
The coil does not consume any active power, i.e. it does not convert electrical energy into any other type of energy.

3. Reactive power
Q = U * I * son? = U * I * 90 ° = U * I * 1 = U * I
The coil takes reactive power, i.e. it stores electric energy in a magnetic field

4. Apparent power
S = U * I = Q the apparent power is equal to the reactive power

Except in this case it is not a 90 ° phase shift.

The shift angle can be calculated as my colleague Szczepan wrote in the first formula. The instantaneous power p is not needed for this task. Continue counting as I wrote.

So it goes something like this:

?u = arcsin (u / | u | ?2) - ?t
?i = arcsin (i / | i | ?2) -?t

Then I know how to count these powers. I have one more question what is THD and how can it be calculated?

I think this should help:
http://sound.eti.pg.gda.pl/student/pe/02-TorFoniczny.ppt

Someone could look at these patterns above, because I am counting and counting and something does not work out. I understand that the uii values are given to me by this device? a | u | i | i | are absolute values?

These patterns you wrote are wrong. By measuring only the current and voltage, you cannot determine ?, you would have to measure the active power with a wattmeter or register the shift between current and voltage on the oscilloscope, otherwise you cannot do it from your measurements. [/url]

So these formulas written by Szczepanr are not good?

The formulas are OK, but I'm not sure if you can read the sample value for a specific time.

Rae wrote:

These patterns you wrote are wrong. By measuring only the current and voltage, you cannot determine ?, you would have to measure the active power with a wattmeter or register the shift between current and voltage on the oscilloscope, otherwise you cannot do it from your measurements.

Well, the author wrote that he measures the value of current and voltage in some time intervals (probably with an oscilloscope), so you can read the phase shift from it.

I have one more question. What is the matter when the voltage is not purely sinusoidal, i.e. harmonics appear


The above-mentioned patterns are probably not good then?