Power supply LC ripple filter
Power supply LC ripple filter
(OP)
I am trying to construct a simple 72 VDC power supply to charge the batteries on a diesel electric locomotive. I need about 5 amps. I used a standard wallbox lighting dimmer, connect to a bridge rectifier to go from 120VAC to variable DC. I thought I should have some filtering on the output to smooth the ripple. I was going to add an LC filter, but have no clue as to the correct values for the inductor or capacitor.





RE: Power supply LC ripple filter
A standard light dimmer will not provide you with isolation from the AC mains. You could easily create a situation were someone stepping off the locomotive into a puddle of water could get shocked.
I recommend a isolation transformer as a minimum. Note - a variac or auto-transformer does not provide isolation either.
RE: Power supply LC ripple filter
Are you at all aware of what you are doing?
You risk yours and other's lives.
Connecting mains via a dimmer and rectifier to a battery will at best create a short circuit to ground and that's it.
If you have disconnected the battery from the locomotive, you may not blow a fuse. That means that both poles of the battery are connected to the mains. You will hurt/kill yourselves if you handle any blank metal in the circuit - including battery poles and clamps.
What is your name and address? I need it so that I can send an officer to your place. It is a crime that you are about to commit.
Gunnar Englund
www.gke.org
RE: Power supply LC ripple filter
RE: Power supply LC ripple filter
RE: Power supply LC ripple filter
A little money for a lot of peace of mind.
http://www2.northerntool.com/product-1/340592.htm
RE: Power supply LC ripple filter
I can see that you were warned by others as well - I will not send an officer.
Adding a transformer will add reactance in the circuit and that may be enough to "smooth" your current. You do not need to smooth it actually. No normal charger works with a pure DC current. It is always composed of chunks of current that flows when charging voltage is higher than battery voltage. It happens 100 or 120 times per second, depending on 50 or 60 Hz mains.
If you need to add a reactor, it shall not be connected to the DC side of the rectifier. It will get saturated at once and does not do any good. It shall be on the AC side to make the charger "compliant" i.e. give it a soft characteristic.
Gunnar Englund
www.gke.org
RE: Power supply LC ripple filter
RE: Power supply LC ripple filter
Gunnar Englund
www.gke.org
RE: Power supply LC ripple filter
Eventually you try to replace as much as you can.
RE: Power supply LC ripple filter