Incredible Surge Issue Experience
Mr Toma wanted us to test surge for both differential of 1.5kV and common mode of 2.6kV. We started out by preparing our overly heavy resistance load. We made sure that the full load current was set correctly and the fans were sufficient to cool down the Rload. Without a fan, I presumption we could fry an egg on it in no time. The Rload was bulky and heavy too. It weighed like a 2 year old toddler who needs constant attention. Good thing that the company invested in a cart. This cart was overly used that we realized later on that it saved our spine and back muscle. We pitied our health card since hasn't been used for a century. Just exaggerating.
We also prepared the scope and 2 differential probes to monitor both main and standby output. Since our product is a medical grade, we really needed to focus on the output voltage waveform. We don’t want to see any shutdown or restart.
So we begun and confidently plugged the PSU into the Rload and then hooked in the input cable terminal into the PSU. The surge tester already had a built in program for surge where one will only click twice for the program to execute. We first started in differential mode at 1.3kV and waited for the output to react. From 0 deg no issue, at 45 deg damn, main output had shutdown then restarted for 200msec.
We were not expecting this to happen because this was a variant where it came from a base model which already passed in surge. As engineer I wondered and questioned my subconscious on what did go wrong? what part of the circuit caused this misbehavior? Was it a set up problem? What changes did we make that might have affected a surge? Was it a firmware issue since we changed so much in the code? Was there a defective component? Did the base model really pass in surge? If yes, was it marginally passing? Are we alone on this issue due to other variant claimed that they had no problem in surge? So many question flash instantly AND YET NOT ONE HAVE BEEN ANSWERED.