inductor voltage lag or lead

[srilankaaa]

Hello
Inductor voltage lag or lead when i apply dc voltage to inductor in parallel does inductor voltage lag or lead current lag or lead

 

[barry]

when you have DC current in an inductor there is no lead or lag, it’s DC.

However, when you first apply DC voltage to an inductor, current will not rise instantly.

 

[srilankaaa]

Hello
when i apply dc voltage to inductor it generate 20V in 9vdc and current when i remove dc it show 20v inductor generate voltage or current

 

[barry]

Hello
when i apply dc voltage to inductor it generate 20V in 9vdc and current when i remove dc it show 20v inductor generate voltage or current

I don’t know what that means.

Yes, when you interrupt current flow in an inductor it will generate a large voltage spike.

 

[D.A.(Tony)Stewart]

Don't confuse DC flyback voltage with AC phase current lagging voltage on an inductor by 90 degrees for a sine wave.

Flyback voltage returns as large spike in the opposite voltage polarity to the polarity of the load (+/-) trying to maintain the stored current in the inductor circulating from the DC source. Upon a dry disconnect, it generates a voltage from equation V=LdI/dt and will be much greater than what was applied.

On fast dry relay contacts there will be thousands of volts! But your meter may not be capturing it accurately because the impulse is too fast. In theory, infinite voltage never occurs because there is always capacitance between opening conductors, and C reduces with radius squared. It might only start from some small pF (picofarads).at a fraction of a mm then capacitance responds to Ic=CdV/dt. Then the slew rate dV/dt reduces with C from the previous inductor current. In fact this LC impulse will oscillate and collapse just as quickly. If it were sustained, you would probably have a DC plasma arc welder with a gap that can sustain the current applied. We call it quenched when the arc cannot be sustained. It is similar to the minimum DC holding current on an SCR or Triac..


Now see if you can compute the actual voltage of the arc. The current limit is limited by the total loop resistance. Try to undertand this before you hurt yourself holding the conductor leads and shock yourself. But for one mA, it is OK. Too much and you now may have a shock through the body and heart (fibrolator.) Be careful.

If you are capable of experiments and want to burn out a surplus relay , let me know and I can show you how to generate kV across the contacts while it burns out asa buzzer ina few minutes, while it burns the contacts out. Wire the normally closed contacts of a SPDT relay in series with the coil and then switch power in series separately. Note that the white light of the arc with ionized air is over 5000'K. Then the contacts will quickly heat up until self-destruction. The inductance of the relay will be in the mH range.

--- Updated Dec 16, 2023 ---

Here are two experiments using a web browser simulation with the scope sampling rate set to 300 ns /step. So if your arc is faster than this you must reduce the sampling time interval. > options> other options> __ time step. It will store up to 2k samples and you can change the play rate with a slider and edit any component values with mouse and/or keyboard.

This ought to raise questions for you to figure out. To see the simulated arc gap arc. see the voltage spike and edit the arc gap voltage. This models ionization time for air about 1 us for small gaps. (bigger for lightning) But one discharged depending on the gap capacitance can be as small as picoseconds or as large as 1 microsecond for lightning (1 us) causing interference you can hear on any AM radio quiet channel.

https://tinyurl.com/yrwzykbk