Electronics > Projects, Designs, and Technical Stuff
Snubber for capacitive loads
ricko_uk:
Hi,
I need to charge a large capacitive-only load of 3,000uF at 250V from the mains using a triac (to switch at zero crossing). Do I need to use a snubber across the triac or are snubbers used only for inductive loads?
Thank you
Circlotron:
If your locality has 240v mains then your 250V capacitor is likely going to charge to 339VDC. Let's see a schematic of what you are proposing to do.
ricko_uk:
Thank you Circlotron :)
Please find schematic attached. The steps/sequences are as follows:
1) At zero crossing I enable the triac for a full cycle (or maybe even 2 full cycles if required) and charge all 4 caps so that across MAINS_GND and UV_SIDE_A there are almost 680V and the same between MAINS_GND and UV_SIDE_A.
2) Disable the triac to isolate the system from mains
3) Discharge the top pair of caps (i.e. across MAINS_GND and UV_SIDE_A) into a coil and wait for full discharge of those 2 caps (still working on the schematic of the discharge part - I am thinking of using a half bridge configuration)
4) Discharge the bottom pair of caps (i.e. across MAINS_GND and UV_SIDE_B) into a coil and wait for full discharge of those 2 caps
5) start the cycle again
Any suggestions or improvements?
Thank you for your feedback :)
Circlotron:
First off, I would put the live side to the junction of the two diodes and the neutral to the junction of the two capacitors. The neutral that would now be at the capacitor junction is at nominally the same potential as mains ground, so grounding the lower capacitor as you have done is going to cause a bit of unwanted excitement. Looking forward to your discharge cct. :-+
TimNJ:
This is surely what was intended..just a schematic typo!
Voltage doubler:
Navigation
[0] Message Index
[#] Next page
Go to full version