Back to Steve's question for a minute. As noted by Larry and others, the 120V system is pretty much for convenience outlets and lighting. It's a 120V (or maybe 110V) plain delta, meaning there is no neutral. And as mentioned above, there is no bonding of any point in the electrical system to ground (hull). So the electrical systems float. You will read 120V phase to phase, and unpredictable values phase to ground because the electrical system is floating. Same with the 450V system, you'd read 450V phase to phase but unpredictable voltages between any point in the system and ground (hull).
The floating electrical system is for tactical reliability, meaning you can inadvertently have a ground occur at any one point in the system with no effect on operation. There are permanent ground detection systems in place that are operated hourly so if a ground does develop, it can be cleared quickly. Obviously a second inadvertent ground would make for a really bad day.
So imagine this for a moment - you could, if you really wanted to, cut the ground bond on a 240V delta, and the delta would continue to work fine. You would loose basic important safety features, a most serious issue, but the system would work. Shipboard systems are just like that except they have 120V transformer secondaries rather than 240V secondaries.
Shipboard circuit breaker and/or fuse panels that are 120V all have 2 pole CB's or pairs of fuses for each circuit. As I said, it's just like a 240V delta except half the voltage. With no neutral, you need to break both sides of the line.
Don't everyone freak out here - but as best I remember I thing the 3 phase color cose was: Black / White / Red.
So with no system grounding and/or neutrals to worry about, checking the electrical system is somewhat simplified. Phase to phase voltages need to be stable, equal and clean. On my boat the turbine generators and the motor generators supplied 450VAC, the operator (me) had voltage regulator adjusting knobs so one could run the voltage up or down a bit (can't remember how far). The 120V systems were supplied by stepdown transformers from the 450V bus, so a voltage spike would seem unlikely. Plus, a 20V variance on the 450V side would amount to about 5V on the 120V side. So I don't know what else there would be to check so far as the electric system goes.
We did have a static inverter, I think 120V. It had lots of problems so we did not use it. But something like that might cause enough electrical system problems to affect other components. You might ask about that - if there is one in this case.
OK - long enough for now I reckon, someone else's turn. By the way Steve, I may know you. Do you happen to work for a large LA area contractor and assigned around the Union Station area downtown? Or used to be anyway?
Radar
