Capacitor only on transformer secondary
Capacitor only on transformer secondary
(OP)
I am looking at a Lestronic II 12 volt battery charger. Looking at the circuit diagram it has 3 secondaries on the transformer. 2 feed thru diodes to supply the 12 v output but the 3rd goes directly to a 3.0 MFD cap. I'm just a tech so I figured I'd ask my uncle, an electronic engineeer for a very long time and he has no idea what that cap does in that curcuit.
The wiring diagram can be seen here http://batterychargerdepot.com/BatteryChargers/13810-74.pdf
So what gives with this capacitor. Thanks for you replies.
The wiring diagram can be seen here http://batterychargerdepot.com/BatteryChargers/13810-74.pdf
So what gives with this capacitor. Thanks for you replies.





RE: Capacitor only on transformer secondary
RE: Capacitor only on transformer secondary
RE: Capacitor only on transformer secondary
The transformer is made with a large leakage inductance which increases impedance so it gets a built-in current limit.
The winding plus capacitor then forms a series resonant load, which draws so much current that the transformer core goes to saturation and the transformer cannot deliver any more voltage.
The voltage produced when core is saturated is constant (same volt-second area regardless of input voltage) and that means that the output voltage is constant regardless of the input voltage - within a range. And that is how constant voltage is achieved.
Compositepro is absolutely right in saying that the resonance circuit works as a fly-wheel. In fact, many CVT:s are used to bridge short interruptions if the grid is unruly. Typically, it can keep voltage up for 50 - 100 milliseconds, if lightly loaded.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Capacitor only on transformer secondary
RE: Capacitor only on transformer secondary