RS Components | Electronic and Electrical Components ... s/4890425/
Am I right in thinking that a common mode choke such as this can be wired in two ways?
The normal way (according to the datasheet) is "both dots on the left". Used for noise rejection, and to prevent noise from the load being passed back into the PSU. Happy to be corrected. I believe in such mode the choke provides almost no inductance and therefore almost useless for power smoothing in a filament supply.
My question is, can such a choke be wired "top dot left, bottom dot right" so that it DOES provide inductance and in conjunction with a cap would provide some smoothing and ripple reduction?
Am I right in thinking that a common mode choke such as this can be wired in two ways?
The normal way (according to the datasheet) is "both dots on the left". Used for noise rejection, and to prevent noise from the load being passed back into the PSU. Happy to be corrected. I believe in such mode the choke provides almost no inductance and therefore almost useless for power smoothing in a filament supply.
My question is, can such a choke be wired "top dot left, bottom dot right" so that it DOES provide inductance and in conjunction with a cap would provide some smoothing and ripple reduction?
Yes, you can always wire a CM choke in two ways. One way gives you CM rejection and high current handling, but almost no smoothing; the other way gives higher inductance (typically x4) and good smoothing but usually much lower current handling.
Sorry for broken link.
Wurth 20 mH ±30% Leaded Inductor, 3A Idc, 160m? Rdc WE-CMB HC | 744825320 | RS Components
Wurth 20 mH ±30% Leaded Inductor, 3A Idc, 160m? Rdc WE-CMB HC | 744825320 | RS Components
Ok thanks DF96. The linked item is specified as 20mH, max 3A. I assume that is when it's wired in common mode (both dots left).
I couldn't see anything in the datasheet about either differential mode connection or inductance and current handling in such a mode. The 3A will relate to common mode I assume.
CM chokes will saturate at very low currents when not wired so currents go in each direction into and out of the dots. Also the inductance is much lower than specified if used single ended. Might as well use a ferrite bead.
The rated current is only if wired as a CM choke. They do provide high impedance to CM signals/noise but none to differential currents.
The rated current is only if wired as a CM choke. They do provide high impedance to CM signals/noise but none to differential currents.
U might get away with some useful filtering if u wire the two windings in parallel. Both dots to same end. U will get 1/4 inductance but it might handle a few tens of mA.
Edit: the filtering is obviously only significant at high frequency.
Edit: the filtering is obviously only significant at high frequency.
If you use the small power factor correction chokes from computer supplies they are useful. They are air-gapped.
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