There are a litany of problems with trying to resurrect an old VFD.
The first and foremost one is that if the VFD has been unpowered for any length of time, i.e. over a year, chances are that the capacitors will be toast shortly after energizing them. If you have a variable transformer you may be able to "reform" them by slowly increasing the voltage over a period of hours, but even then it may not work if the electrolyte has already dried out. On top of that, the generally accepted lifespan of a capacitor is 5-7 years. Yours are 20 years old! Once the caps are gone, the replacements would be more expensive than buying a new drive.
Problem #2 is the fact that all of the little caps on the PC boards are also old and likely to fail.
Problem #3 is that in most cases, a 480V drive cannot accept 240V 1 phase as an input, it will likely trip off on Low Voltage and/or Phase Loss even if you manage to get it to energize. In 1987 I doubt that AB even bothered giving you an option of disabling the LV/PL protection as some mfrs do now, because they never considered the possibility of using it as a phase converter, especially on a 480V drive. Most of ABs current drives will not allow you to do that.
The last problem I can think of is the Darlingtons. They are not likely made any longer, so if you manage to find some, they will be very very expensive.
Then there is a problem with what you want to do in general. A VFD does not make for a good 3 phase converter for powering a facility. The act of switching a motor on on the downstream side of the drive puts a tremendous strain on the transistors, what is called a di/dt surge (di/dt stands for delta-current over delta-time). Each time you do it, even if the transistors survive, you are doing incremental damage to the silicon substrates. In essence you are chipping away at their life span and it usually takes only a matter of months for them to fail, if not sooner. If you want to produce a 3 phase system for distribution throughout a shop, use a rotary phase converter. If you want 1 converter for 1 motor, use a VFD.  |