- #1

Mark_Djorn

- 6

- 2

- TL;DR Summary
- Drift velociry for Alternating Current

Concept of power transmission.

Reactive Power and reverse power

Hi All

I hope this topic makes sense for this forum and somebody can help me to understand.

This is what I understand (please allow numerical approximations):

1. Electrons move in a conductor at a speed anywhere near the speed of light.

2. Electrons gain actual velocity (drift) only when supply is ON. Propagation of EM field is about 270.000 km/s but actual drift in the order of mm/ or ųm/s according to current and conductor section

3. For DC, drift velocity can be calculated.

Now, am I right to say that, in AC, actual average velocity is zero? That's because in a PERIOD, electrons move back and forth. I could calculate the drift in half a period, but in a period would be zero. Correct? This means there is no actual transmissions of electrons from source to load, right?

Under the assumption above, why we keep talking about "power transmission"? As a matter of fact, there is nothing moving from source to load. Electrons simply move back and forth while performing work and the actual drift is in the order of mm/s in obe direction, and same drift in opposit direction. Hence leaving their velocity to zero. Correct?

Under the considerations above, can anyone explain the concept of "reactive power going back and forth from source to load" in cases where power factor is lesser than 1?

I cannot figure out the concept of power "moving" or simply the concept of "reverse power". If in average electrons don't actually travel, what's truly causing reactive power to go back to the source?

Thank you very much in advance!

I hope this topic makes sense for this forum and somebody can help me to understand.

This is what I understand (please allow numerical approximations):

1. Electrons move in a conductor at a speed anywhere near the speed of light.

2. Electrons gain actual velocity (drift) only when supply is ON. Propagation of EM field is about 270.000 km/s but actual drift in the order of mm/ or ųm/s according to current and conductor section

3. For DC, drift velocity can be calculated.

Now, am I right to say that, in AC, actual average velocity is zero? That's because in a PERIOD, electrons move back and forth. I could calculate the drift in half a period, but in a period would be zero. Correct? This means there is no actual transmissions of electrons from source to load, right?

Under the assumption above, why we keep talking about "power transmission"? As a matter of fact, there is nothing moving from source to load. Electrons simply move back and forth while performing work and the actual drift is in the order of mm/s in obe direction, and same drift in opposit direction. Hence leaving their velocity to zero. Correct?

Under the considerations above, can anyone explain the concept of "reactive power going back and forth from source to load" in cases where power factor is lesser than 1?

I cannot figure out the concept of power "moving" or simply the concept of "reverse power". If in average electrons don't actually travel, what's truly causing reactive power to go back to the source?

Thank you very much in advance!