Depending on what they make some companies may still want an ungrounded delta with ground fault monitoring. If the operation needs to keep running and shut down it a orderly fashion under fault. We had a chemical reaction product that once you added water it had to mix for 45 minutes or it was $$$$$ money for cleanup.
Cowboy
Exactly, it's an older concept still used in some industries. I call it the
"Damn the torpedoes, full speed ahead!" philosophy. In an industrial facility if you have an ungrounded delta* system and you get a ground fault anywhere on it, the system goes from ungrounded delta to "corner grounded delta" for all intents and purposes, so the plant keeps on chugging along because no breakers trip. It's not ideal and you will want to KNOW that this has happened, hence the requirement for a "ground monitoring system", but again, nothing automatically shuts down. I used to work at a steel mill, that's what we had. If the arc furnaces shut down because a ground fault somewhere else caused the main breaker to trip, it would cost
millions to rebuild. Ungrounded delta systems were common at one time, especially during WWII when war production took precedence over life and limb. But it's fallen out of favor now, especially with more modern ways to detect and isolate a fault at the lowest possible level, which also prevents that major shutdown. In addition as mentioned earlier, anything with power electronics will NOT like being connected to a delta system, so VFDs, DC drives, UPS systems, any large 3 phase power electronics. Most utilities now will either not even offer ungrounded delta any more or if they do (which is apparent in this case), they usually make it onerous.
* aka 3 wire in this context, but I agree it's not the best way to refer to it. In a lot of cases you may have a 4 wire secondary on the transformer and ground the X0 point, but if there are no loads that need a neutral, for instance an MCC feeding all 3 phase motor loads or other small single phase transformers, nobody runs a neutral wire out of the service entrance device. So everything after that can be referred to as "3 wire" but it is not a delta system, it's 3 wire from a solidly grounded wye system.
Float glass production lines are a bit like that. Stop it and the liquid glass solidifies in the furnace. Takes weeks to clear it out.
The few we did were DC drives with massive battery back up and mechanical arrangements that allowed two inputs to the gearboxes.
Sorry mods - a bit off topic,
Not really off topic. He did ask why anyone would use it, you gave an example. :thumbsup: