Hey there. I have a bunch of VFDs that have been sitting in storage that need reforming and currently my company doesn't have a reforming process. I am trying to price a couple of high voltage regulated power supplies to do this process and when I was reading through Rockwell's documentation on the subject they are very specific on the voltage required for this process, however, when it comes to the current requirement they only say not to exceed 500mA. So my question is, when reforming these capacitor banks do I need to source a power supply that can output 500mA or is it ok to use one that has substantially less. I am finding some power supplies that are in the 2-6mA range for decent prices (my company isn't that big so we do have a strict budget). I can't find any documentation that says you need at least a certain current. Any help you all can provide will be much appreciated.

 

Reforming is a process of charging the capacitor. Thus, you can use the formula for time and current (voltage/resistance) , such as here: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capchg.html or here: https://www.allaboutcircuits.com/tools/capacitor-Charge-and-time-constant-calculator/

Because chemical changes are occuring, those time calculations should be considered a minimum.

 

Welcome to AAC!

I can't find any documentation that says you need at least a certain current

Rockwell is specifying a power supply that can provide the forming voltage at a maximum current of 500mA. If you use a supply that starts current limiting, you won't get the correct forming voltage.