Electronics > Beginners
transients in capacitor droppers
LaserTazerPhaser:
Is the zener of any use if the application is for electroplating? Electroplating with this form of supply can be hazardous but its useful since it bares a high DC voltage which readily overcomes electrolytic resistance especially the more series dropper capacitors the smaller the resistance of the fusible resistor.
However a TVS zener is needed for loads involving semiconductors after the rectifiers.
Gyro:
You really need something to kill the supply if one of the series capacitors goes short. The Zener will act as a clamp in these circumstances - either blowing the resistor (hence the fusible, flameproof bit) or, less likely, the fuse. Expect the Zener to go short too.
In your circuit , as originally drawn, you show a 470uF (so presumably electrolytic) capacitor on the output of the bridge. Without the Zener to clamp it, the voltage across it would either rise past its rated voltage, or store up enough energy to really make a splash.
As you say, using this form of non-isolated power supply for Electroplating use is hazardous but you're on your own with that one - at least if you have nobody else to take safety responsibility for.
EDIT: This is becoming rather more like Frankenstein's laboratory - I think this is the first time that you have revealed that it's to be used for electroplating.
Doctorandus_P:
For small things such as LED's a resistor is often used to limit the inrush current.
With a 10uF capacitor the steady state current is a lot higher hen needed for a LED, and this makes a a simple series resistor less attractive, because of excessive engy loss.
You may want to consider to use an inductor to limit inrush and transient currents, and also add a resistor to lower the Q of the LC circuit just enough to limit peaking.
LaserTazerPhaser:
That 470uF filter capacitor would not be present for electrolytic loads. The filter cap was only for loads which had semis involved in which case a TVS would be implemented along side it, also its voltage rating would be well over the fullwaved peak voltage.
The capacitor droppers are 630v and they are self healing. The only things which can cause the series capacitors to short out is over voltage, heat and defects. The zener TVS would likely combust, they are only intended for short duration transients, they aren't made to conduct shorted mains supply.
What off the shelf inductor packages & values are ideal? Currently only thru hole torroids appear usable for this. But there are those costly inductors which are made with flat copper wire which can be surface mount, but they have so much ferrite it might saturate and short out for almost any inrush current.
Gyro:
If the load is a plating bath, you are probably past the point where you care about noise spikes - they will simply be integrated by the plating process. Worst case, the capacitors will self-heal themselves to death.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version