Hi Gene, Sorry it took me a while to respond.
Re-reading this, Les, I have to ask how old that VFD is? Anything over 4 or 5 years, I would expect that the capacitors would be suffering from poor ESR, which isn't a test feature available on a utility DVM with a microfarads test function.
It is a few years old. The noise I was referring to was not from the main switching transistors but rather from the internal logic power supply. The reservoir caps may have a higher ESR than they originally had but they are ginormous compared to what you would normally fit on a switch mode PSU so their ESR is probably still much lower than most SMPSs would see. Switching noise from the inverter with the spindle running is much less that it's PSU noise.
This inverter is one I bodged on because the original one failed. I bought this inverter on eBay 'Fitted but never used'. Yeah, right. Going by the accumulated dust it had done many hours on a woodworking machine.
I suspect the original failed due to dead caps. It started faulting under heavy load then under light load and now won't even start the spindle. To be fair I am subjecting the caps to a higher load they they were designed for. The inverters were designed for 415V 3 phase and I'm feeding them 415V single phase (I don't have 3 phase).
I do have an LCR meter but I haven't got around to removing the inverter and testing it.
Les ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
