Johnny B:
Just wanted to toss a little information in this thread regarding your scenario.
1st off, the wirenuts probably fell off due to these factors:
<OL TYPE=1>
[*]Constant vibration of the Core resonating the entire fixture and conductors,
[*]Heat build up added to the vibrations, causing expansion and contraction,
[*]Wirenuts probably weren't installed correctly to begin with, amplifying the above situations.
</OL>
Seen many Wirenuts which have fallen off due to the scenarios above - along with Wirenuts that fried to dust!
If the connection between the Autotransformer's output and the Reactor's input becomes faulted, this will draw excessive current.
This fault can be from a fried winding or a direct ground fault due to a loose Wirenut falling off, allowing the connection to contact the grounded fixture.
This fault will be limited by the Reactance of the "Primary" circuit, so currents will not act like a direct fault does [with the sparks show and trip breaker real fast].
Depending on the point of the fault, the circuit may not even draw an abnormal overcurrent / overload.
However, if the overload current is 2 or more times that of the designed operating current - and it flows continuously, this will barbeque the coil[s] and the core.
Now if the Reactor circuit becomes faulted - such as a short circuit, this will only load the complete Ballast upto the rated input current flow. This will end up frying the Reactor coil after continued use, since the Reactor is producing lots of heat [the True Power - in Watts - is dissipated in the Reactor coil, not the lamp].
Your example of 50 Amps is not uncommon for shorted Autotransformer sections on CWA / HX Ballasts.
Circuit wise, the Multiwire circuit is fine. The Wire size should be large enough to keep the voltage drop as low as possible.
Don't forget about increased Ambient temperature in these areas! That's one more adjustment factor to use for conductor sizing.
Balancing three lines across one common grounded conductor may be done with an increased common conductor size - to help out with the Harmonics which most likely will pop up.
Harmonics can get generated between components of one fixture and components of another fixure[s]. If a Capacitor from one Ballast can resonate the primary coil on some other Ballast, this will cause currents to flow between the two luminares.
Just a little THD info!
Next, the Ballast circuitry you described is for a Constant Wattage Autotransformer type Ballast [known as "CWA"].
With the CWA Ballast, the Starting current is closely equal to the running current - meaning the level of current flowing will be almost the same no matter if the lamp is starting or operating for 1 hour.
With Hi Reactance ["HX"] and Straight Reactor ["R"] type Ballasts, the Starting current varies from the running current.
These normally have 1.25 to 2x the starting current level [125% to 200% + or - of the running current for starting]. One has lower starting current, other has higher starting current.
One last item would be regarding Capacitors.
Power Factor Caps which have become open or shorted will cause the Ballast to draw higher line current [>150%].
Your Luminare specs should be something like this:
[1] 400 Watt M59 Metal Halide lamp [mogul base / 350 volt lamp].
CWA Ballast - "Quad" Input
120 VAC [4.0 Amps],
208 VAC [2.3 Amps],
240 VAC [2.0 Amps],
277 VAC [1.7 Amps].
Capacitor = 24 MFD @ 400 VAC.
Select a 4 Amp 300 VAC Fuse for protecting this Ballast.
For HID Ballast Schematics to check over, refer to
HID CWA Ballast Schematics in the Technical Reference section.
For other Schematics, see the
Menu For Technical Reference Section to find additional Schematics via links.
Good luck.
Scott s.e.t.
