Loading the magnetic field of an inductor

[Jdo300]

Hello all,

I have a simple experiment I'm working on where I am pulsing square waves into an air-cored coil with a high inductance (in the mH range). I am wondering if there is a way to calculate what pulse width, on the square wave, I would need to use to completely load the magnetic field of the coil, but no more. I want to see how much of the stored energy I can get back from the field (minus the resistive losses). Ideally, I want all the input power to go into the field and then the pulse would shut off before extra power is wasted and unnecessary current flows through the coil. Any pointers are welcome.

Thanks,
Jason O

 

[ice109]

you can't avoid resistive losses, it's not like an overflowing cup type thing where if you "fill up" the field and then stop none will be lost to resistance.

 

[berkeman]

Hello all,

I have a simple experiment I'm working on where I am pulsing square waves into an air-cored coil with a high inductance (in the mH range). I am wondering if there is a way to calculate what pulse width, on the square wave, I would need to use to completely load the magnetic field of the coil, but no more. I want to see how much of the stored energy I can get back from the field (minus the resistive losses). Ideally, I want all the input power to go into the field and then the pulse would shut off before extra power is wasted and unnecessary current flows through the coil. Any pointers are welcome.

Thanks,
Jason O

I'm not sure what you mean by completely loading the coil. The current is limited by the source voltage and the DCR of the coil. You can calculate the LR time constant, and charge the coil for a few time constants per pulse. What's your DCR? (If it's low, be sure to subtract out your DVM lead resistances in the final reading.)