Power Supply

vksamael · 22nd October 2009, 08:03 AM

I have 2 capacitor 33000uF/70V and what resistor i have put on capacitor power suplly is 45V ( + and - and GND )
thanks

star882 · 22nd October 2009, 02:57 PM

45v/current rating gives you the resistance to use for full load testing. Such a resistor would likely be big and expensive, so it might be possible to use light bulbs or heating elements as a test load. (Calculate resistance with original voltage^2/original wattage.)

If you want precharge, use 45v/peak current rating for the resistor to limit inrush current. You'll need a relay to bypass the resistor after precharge.

AndrewT · 22nd October 2009, 03:16 PM

+-45Vdc sounds like you are using a 32Vac or 33Vac transformer.
You can attach the two 33mF smoothing caps direct to the rectifier without needing a slow charge resistor.

I would fit a soft start for the transformer, again a resistor or thermistor with a relay bypass using a 200ms delayed timer.

22nd October 2009, 08:03 AM	#1
vksamael diyAudio Member Join Date: Dec 2006	Power Supply I have 2 capacitor 33000uF/70V and what resistor i have put on capacitor power suplly is 45V ( + and - and GND ) thanks

22nd October 2009, 02:57 PM	#2
star882 diyAudio Member Join Date: Mar 2007	45v/current rating gives you the resistance to use for full load testing. Such a resistor would likely be big and expensive, so it might be possible to use light bulbs or heating elements as a test load. (Calculate resistance with original voltage^2/original wattage.) If you want precharge, use 45v/peak current rating for the resistor to limit inrush current. You'll need a relay to bypass the resistor after precharge. __________________ "Fully on MOSFET = closed switch, Fully off MOSFET = open switch, Half on MOSFET = poor imitation of Tiffany Yep." - also applies to IGBTs!

22nd October 2009, 03:16 PM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	+-45Vdc sounds like you are using a 32Vac or 33Vac transformer. You can attach the two 33mF smoothing caps direct to the rectifier without needing a slow charge resistor. I would fit a soft start for the transformer, again a resistor or thermistor with a relay bypass using a 200ms delayed timer. __________________ regards Andrew T.

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