The single voltage rated MCBs are acceptable for line to line or line to neutral loads at voltages up to 240 VAC.
The double voltage rated MCBs are acceptable for line to neutral loads at voltages up to 230 VAC, and line to line voltages up to 400 VAC.
Bill
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"Why not the best?"
Jimmy Carter
The dual rating means phase to ground can't be higher than 230V but that 2 (or 3) breakers ganged can be used on 400V phase to phase power. So, that means you could use it on a solidly grounded wye connected power system that is 230V phase to ground/400V phase to phase. 2 (or 3) ganged can be used to provide 400V to a load device.
A single pole dual rated breaker like in your picture can't be used any differently than a single voltage rated breaker of the same voltage.
I believe this dual rating is only seen on what's called a supplemental breaker or supplemental protector in North American standards which have limited applications.
