Ok! I got the covers painted, then I turned my attention to the electrical portion of the power supply. I began by reinstalling all of the indicator lights and switches that were removed for painting. The process was relatively uneventful, although one of the contacts for an indicator light broke. It was soldered originally, and under spring pressure, but a little shimming allowed me to extend the terminal so it could be re-soldered.
I had a bit of trouble following some of the wires when reattaching, although in the end all was well. While the wires are all identified with tags, some of the tags were buried in the loom.
I had previously removed the switch used for switching the capacitors. It had been rusted to the point where it would not function. A simple device, a series of cams which active a serious of microswitches, which, in turn, activate numerous contactors. The shaft was polished, along with related components, with contacts cleaned, then it was re-assembled, and had been placed in storage until needed. It was retrieved and installed. I now regret I took no pictures of that operation. I also dismantled the switch used for switching the furnace voltage, and didn't get pictures of that, either. There's a high frequency transformer included with the machine, with eight positions. Voltage is selected so full power can be achieved, plus the capacitor switch allows for power factor correction, so the unit operates at unity. The contacts were burnished and the switch cleaned up and lubricated, then reassembled.
It is important to understand that power factor is ever changing with an induction furnace, as it relates to the state and size of the charge. As it melts, unity shifts, so it requires constant attention. The third generation of induction furnaces are solid state, with power factor adjusted without intervention. My dinosaur unit (motor generator) lacks that nice feature, but I'm happy to have the unit, as a solid state induction furnace is well beyond my finances.
In order for the generator to not be able to run wild, there's a detector (a lightning arrestor is used) to instantly kill the power that excites the generator. A disruption of power to the furnace can give cause for an almost instant high voltage spike of the generator, so this unit is intended to prevent such a situation, which destroys the generator. There is no simple test to determine if the arrestor was good, or not, so I perused ebay to see if I could find a new one. Turns out the one in the machine is obsolete, but the replacement, which mounts slightly differently, would suffice. I found an offer to buy them, new, for $20 each, so I purchased a pair, one as a backup, should it be needed. I had to modify the mounting ever so slightly, but it installed without issue. That circuit is activated ONLY upon failure, at which time the far left red light on the control panel is lighted. It is never lighted otherwise, not even upon starting the unit. All of the others show red until they are reset, which then permits the motor starter to engage.
While the 400 amp disconnect had power, I had not yet run leads to the supply, but I wanted to determine if the control circuits were operational. In studying the prints (provided to me years ago by Ajax), I determined that the entire control system operated on 120 volts, so I removed the secondary leads from the transformer in the power supply and connected the two leads directly to 120 volts. By shunting the water pressure switch, I was then able to try each of the controls. I was not pleased, as the exposure to weather, coupled with the many years the unit sat out of service, the control relays were not reliable, and the relays that switch the capacitors, as well as the contactors for the motor starter and the furnace power were extremely noisy.
When the button was pushed to reset the relays, a necessity in order to start the motor/generator, some of the control relays would, some would not, and it wasn't always the same units that failed to work. Here's a picture of the relays, which are the seven square items in the second row of components.
Failure of the relays to reset was random. That would make the startup of the unit questionable, so I tried to find new relays, only to discover that they were obsolete, thus, no longer available. It was virtually impossible to access the contacts so they could be cleaned, as the assemblies were staked together, and the lower set of contacts were not accessible even when they were opened. I decided that new relays would be required, so I perused ebay until I found a deal on several, which were purchased. They were easily changed to function as needed, so I decided to mount them at the bottom of the panel, where there was just enough room to do so without interfering with other details inside the cabinet. I also concluded that using the original relay bases would simplify wiring, so each relay was gutted, and a grommet installed in the left side of the housing so wiring could be introduced through the housing. A proper sized grommet was fitted to protect the wires from the sharp edges of the thin sheet metal covers. By removing the original contacts, I could solder the wiring to the holes where they were mounted. That required bending them, so the lower contact could be removed, which was to my benefit, as it allowed for much easier soldering. You can see the added relays in the picture, below, along with the wiring leading to the original relay housings. There was adequate room to mount the new relays under the existing electrical devices, so I made a rack and did so.
The circuit discussed above, the one with the lightning arrestor, triggers a DC circuit. It required a different relay, which you can see is clearly different from the AC relays. It's the one on the right. Interestingly, this power supply is old enough that rectification for the various DC circuits is accomplished by various selenium rectifiers. I was really showing my age when Patio and I discussed them. He is a modern day electrician and had never experienced one.
I addressed each of the contactors by burnishing the contacts, and hand cleaning the rust on the armatures that was preventing each from making intimate contact. That eliminated the vast majority of the noise each was making, although they all have the characteristic hum of such items. I figured the limited noise wouldn't be much of an issue when the unit was in operation, so I considered my efforts to be a success. They all worked, and I could move on with other issues.
Out of time for now, but I'll add to this in the near future. Thanks for looking.
H