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I managed to make variable voltage and current for dummy load using IGBT with PWM control from Arduino, I plan to use the output as a variable power supply. The output from IGBT is a square wave so I plan to use lLC low pass filter from IGBT output to make it pure DC.

How to determine/calculate the spec of inductor and capacitor for up to 100A usage? I tried to simulate with Multisim and tried different values and get 10mH and 4700uF. Is there any issue to apply this?

I found a shop that can make custom inductors, I just need to enter the value of inductance and current and it lists several types with different turns and resistances but same inductance and ampere. I'm not sure with the physical size, it states really small, is the spec legit?

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  • \$\begingroup\$ Have you checked the price of a 100 A 10 mH inductor yet? \$\endgroup\$
    – The Photon
    Jun 7, 2020 at 14:59
  • \$\begingroup\$ What switching frequency do you have and how much ripple can you tolerate given that pure DC is as commonplace as leprechauns? What load range do you want to consider (open circuit down to what resistance)? Is the load largely resistive or does it involve pulses of current? \$\endgroup\$
    – Andy aka
    Jun 7, 2020 at 15:10
  • \$\begingroup\$ @ThePhoton I found a shop that can make custom inductors (script.google.com/macros/s/…) I just need to enter the value of inductance and current and it list several type with different turn and resistance but same inductance and ampere, I'm not sure with the physical size \$\endgroup\$
    – user254674
    Jun 7, 2020 at 16:38
  • \$\begingroup\$ @Andyaka I'm using arduino for PWM with 500Hz/900Hz, I want to use the output to turn on 48V DC fan so this one don't need high current, but I'm thinking about use the output to charge high capacity battery which I can change the output Voltage. I'm not sure about ripple tolerance for that application \$\endgroup\$
    – user254674
    Jun 7, 2020 at 16:53
  • \$\begingroup\$ @user254674 A 100 A-rated 10 mH inductor is going to be massive. Possibly the size of a mini-fridge. And it's going to have a cost that goes along with that--at least a few hundred, probably a few thousand dollars. \$\endgroup\$
    – Hearth
    Jun 8, 2020 at 15:59

1 Answer 1

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https://electronicbase.net/low-pass-filter-calculator/

10mH and 4.7mF give 93Hz cutoff frequency.

Assuming your PWM is at 930Hz. Power falls as 20dB (x100) per decade (x10 frequency). Your filter is just 1 decade below working frequency in this example. So AC power that remains is 20dB lower, or 1% left. It is likely okay.

https://en.m.wikipedia.org/wiki/Cutoff_frequency

Practicality: 10mH 100A is a welder transformer. 10kg.

TLDR: For each x10 frequency difference, AC power drops by x100.

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  • \$\begingroup\$ Thank you for the answer, I found a shop that can make custom inductors (script.google.com/macros/s/…) I just need to enter the value of inductance and current and it list several type with different turn and resistance but same inductance and ampere, I'm not sure with the physical size, It state really small \$\endgroup\$
    – user254674
    Jun 7, 2020 at 16:54
  • \$\begingroup\$ sorry, cant see the link (its required to login. i dont use google) \$\endgroup\$ Jun 7, 2020 at 16:59
  • \$\begingroup\$ I added the image of the inductor offfered \$\endgroup\$
    – user254674
    Jun 7, 2020 at 17:28

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