Hello. I am trying to test some used 450V 12000uF electrolytic cornell dublier capacitors. I do not know the age of these capacitors, nor what conditions that they were used in. Visually I can tell by their terminals that they were once used, though they look pretty new and to me their capacitance values seem pretty high for them to be older than 5-10 years.
I have a Keithley 237 SMU that I've been using to test them. After looking online I saw a method using a 470k resistor in series with a capacitor connected to a DC supply of 450V. This would give about 1mA initial charging current. However the CDE application guide, on page 16 it says to apply the rated voltage in series with a 1k resistor for 30 minutes, for capacitors that have been sitting for 5-10 years. For the first capacitor that I tested, I put the SMU to constant voltage mode at 450V with a compliance current of 10mA. I let it sit for about 5 hours after it was brought up to 450V. Initially my leakage current was swinging from 7-9mA, but as the time went on it settled to about 0.5mA-1mA.
My questions are thus: Is this an acceptable leakage current for a good electrolytic cap? And would I get better results if I set my charging current limit to 1mA? From what I've read it seems that when reforming, the reason to keep the charging current low, is to ensure that there is no excess heat buildup inside the cap, but I don't know if there are other reasons unclear to me. Also most of what I found online about reforming was regarding very old electrolytics inside old tube equipment, and not for modern caps.
Here is the link to the application guide: (Go go page 16 ~ Shelf Life)
Thanks,
Rob
I have a Keithley 237 SMU that I've been using to test them. After looking online I saw a method using a 470k resistor in series with a capacitor connected to a DC supply of 450V. This would give about 1mA initial charging current. However the CDE application guide, on page 16 it says to apply the rated voltage in series with a 1k resistor for 30 minutes, for capacitors that have been sitting for 5-10 years. For the first capacitor that I tested, I put the SMU to constant voltage mode at 450V with a compliance current of 10mA. I let it sit for about 5 hours after it was brought up to 450V. Initially my leakage current was swinging from 7-9mA, but as the time went on it settled to about 0.5mA-1mA.
My questions are thus: Is this an acceptable leakage current for a good electrolytic cap? And would I get better results if I set my charging current limit to 1mA? From what I've read it seems that when reforming, the reason to keep the charging current low, is to ensure that there is no excess heat buildup inside the cap, but I don't know if there are other reasons unclear to me. Also most of what I found online about reforming was regarding very old electrolytics inside old tube equipment, and not for modern caps.
Here is the link to the application guide: (Go go page 16 ~ Shelf Life)
Thanks,
Rob
