Architecture of Mex Starter

If it's what I'm thinking get rid of it as soon as possible.

They are DANGEROUS!

Wow, I've never actually seen one, but when I worked for Klockner Moeller we had cam switches with that functionality available. I just never saw anyone even consider using one. Here in the US we used to have what we called "one-armed bandit" starters, or "manual compensators" which were manually operated reduced voltage autotransfomer or reactor type starters. The "one-armed bandit" moniker came from their resemblance to slot machines, plus their tendency to "rob" the occasional hand or arm from the operator when they went bad. They are all but gone now thanks to new more stringent arc flash protection regulations. Those things were mayhem in a box. I can't imagine that a star delta version would not be worse.

We used them for 300HP MG sets, some were 550V star delta like the one above. Others were 3.3KV autotransformer. All the same lay out. Handle horizontal for off, down for start and then you had to swing the handle back through the off position to up for run where it mechanically latched.

To be honest I was sad to take the last one out. The last being a 550V Ellison unit. The MG sets had become my pets (I think that came about because I was the only one that was daft enough to work them).

We also had rotary converters and mercury arc rectifiers and a couple of these new fangled things using diodes! The only ones I got photographs of

These were standard Ellison OCB's

Works of art...

Try L & T or Salzer Websites. They do have a diagram, I suppose, for Manual Star Delta Starters. But, please refer them only to understand. Do not use them as they are extremely dangerous as the Change-over time is decided by the operator and there could be premature or post-mature change overs, causing flash-overs.

Or drag a retired Zen master like Tony S out of retirement (or some other guy with just the right touch)?

If those breakers cannot be operated under load, do they ever self-trip under load? If not...what exactly do they do?

There in the control room of a lift bridge in Liverpool. The bridge has been restored so it can carry traffic again but the mechanical side of it was beyond repair so the switchgear is redundant.

We used the same type of OCB's for plant distribution and motor starters. Many years ago

There was one of these installed on a Wadkin circular saw for rip-cutting timber. It had a 26in-diameter blade. Starting in star was exciting. Starting it in delta pulled out the supply fuses to the building...

Thank goodness it has gone now.