I've read here and there "get the most henrys you can fit in your chassis" when it comes to chokes. Lets say I want an LCRCLC filter, and I want the supply to be relatively stiff to around 300mA. I find a 16H 300mA choke that fits mechanically for L1, and great, I can also fit another 16H 300mA choke for L2. Why on earth would I buy a 5H or 9H 300mA choke when these 16H guys fit just fine? The Duncan PSU model shows significantly less ripple with 16H chokes. Am I missing something when it comes to compromising choke henrys against chassis restrictions? The larger chokes also don't need as large capacitors. I asked AI to compute an ideal reactance capacitor size for an LC filter at 120hZ with 16H choke, it came back with a nice 110uF, nice that is DC link territory size wise film caps. With a 5H choke it computed a capacitor size much larger which puts me into using electrolytics, which I am holding on the non-compromising side. Everything is a compromise at some point even against the mechanicals of the chassis. Should I buy these 16H chokes, or go back to the drawing board?
A choke size is determined by:
-Core type
-Core and window size
-Wire gauge, Rdc of choke
-Rated inductance
-Maximum Idc before saturation (both go together)
-Maximum ripple at the required frequency before saturation (both go together)
You can have have both 5H and 16H @300mA on the same core and the same filling of the window. The 5H choke might have been wound with a thicker wire, so lower Rdc. If Rdc turned out to be the same as the 16H, meaning identical turn count, then there would be flux density headroom, which could be used for ripple voltage accross it (suitable for choke input duty). If it wouldn't be used with a higher ripple voltage, then it could withstand more Idc, 960mA.
-Core type
-Core and window size
-Wire gauge, Rdc of choke
-Rated inductance
-Maximum Idc before saturation (both go together)
-Maximum ripple at the required frequency before saturation (both go together)
You can have have both 5H and 16H @300mA on the same core and the same filling of the window. The 5H choke might have been wound with a thicker wire, so lower Rdc. If Rdc turned out to be the same as the 16H, meaning identical turn count, then there would be flux density headroom, which could be used for ripple voltage accross it (suitable for choke input duty). If it wouldn't be used with a higher ripple voltage, then it could withstand more Idc, 960mA.
What is your goal for filtering at each supply takeoff point? What's necessary and what's overkill? Chokes are expensive and heavy. The wheel has already been reinvented about a billion times.
Use the "stepped load" feature in PSUD2 and check your supply for ringing. Most relevant part here is the last LC. Calculate values or DCR, L, and C to get as close as possible to a Q of 0.7.
Calculate critical inductance for your L1 if you want to use a choke input filter.
60Hz power mains, and full wave rectification (120Hz full wave):
Critical Inductance = 350/Load mA.
Example, 300mA load. 350/300mA = 1.16 Henry choke
It is choke input. Surely a 16H 300mA choke would hold up in first position? I can even fit their 12H 400mA version if that is better. Or their 10H 500mA version. All of which have the same physical size. So 16H 300mA, 12H 400mA, or 10H 500mA all fit. Bot the power transformer is rated 350mA the expectation is to make a 300mA PSU, but if oversizing the first choke current rating and reducing the H to 12 or 10 is better I'd do that. Is critical inductance a minimum or a figure to meet exactly?