108/187V Panelboard

[ElectricWoj]

Couldn’t find the correct section to post this in. I am working on a project and we are gathering existing conditions. I have come across a westinghouse split bus panelboard with a voltage of 108/187V.

https://flic.kr/ps/3XMhoj

There’s 120v per phase that enters a buck transformer that brings the voltage down to 108v. The panelboard has a nameplate of 108/187v.

The panelboard has 4 sections. 1 for main breakers. 2 sections for split bus panels. 1 section of ASCO contactors.

Has anyone ever seen something like this? I was able to do a bit of research on this an found out that mercury/metal halide blubs run efficiently on a voltage of around 100V. Could this panel have something to do with this? Maybe the lower voltage eliminates the need for a ballast?

Panelboard was installed sometime during 1970s

 

[hillbilly1]

I’ve seen buck/boosts used as a dimmer for HID fixtures, I wonder if the contactors are the shunts for the dimming?

 

[tortuga]

Can you tell us more about the use of the building?
My guess is it was sized for a large amount of old incandescent lighting (stage film video?) or to run equipment such as 200V motors from Japan.