The old DOS PC running a Phenix Recloser for one of our customers gave up the ghost recently. The use of computer hardware, software and machine hardware means that everything needs to work for anything to work at all. This can make it quite difficult to figure out which sections were damaged and which were still working. So the best option available to investigate further was to dis-connect from the PC and I/O card and use our EDM (Electronic Diagnostic Module) to take over the role of the central controller.
The EDM was able to be fairly easily interfaced to the rest of the machine using the analog and digital IO that we have on board. An add on card was required in order to be able to read the 160V that was required to get enough current for the breaker to trip.
The unit uses two pairs of parallel Variacs to control the output voltage and a small DC drive and motor via a gearbox to do the turning. Position feedback was from a pot on the Variac shaft giving some proportion of 0 to 5v as feedback. The control needed to put a position control loop around the Variac, operate CB under voltage coil and several contractor drives, and look at and interpret the results in terms of minimum tripping current, times to trip and re-close and number of rr-closes. With the EDM in control we were able to verify that the power section of the machine is fully functional. Here is a graph showing a test in which there was two re-closes performed.
The test results included
- Initial tripping current = 21.1 amps
- 1st Reclosing time (1047 – 955)/50 = 1.84 sec
- 2nd Reclosing time (1389 – 1306)/50 = 1.66 sec
Now that we understand the unit and have proved that most of it is still functioning we can either commit to more time trying to repair the original computer or look at our options for replacing the old computer with a more modern interface.