Square D Rating Columns

[drcampbell]

I encountered an old Square D PAL circuit breaker yesterday. It uses something they call "rating columns" to configure the breaker's operating current.
Visually, I can't see that these are anything more than a plastic stick. There are no electrical contacts, no external clues as to how they work. They're about the size of a toothbrush.

First question: How do they work? Do they come in different lengths and actuate a mechanism that's not visible without disassembling the breaker? Complete a magnetic circuit with a larger or smaller piece of iron inside each different rating column? Black magic?

Second question: Do you know where I can get some information on these breakers? Installation/operation/maintenance manuals, perhaps?

 

[jim dungar]

They determine the Long Time rating of the breaker. The PA breaker is thermal magnetic, so they have something to do with the heating of the thermal 'bimetal'.
In all the years that I sold these, I never bother to figure out how they worked. I always thought of them as resistors, although they could be heat sinks.