The TMA trip gives you an adjustable thermal overload curve plus a fixed magnetic short-circuit pickup — useful for motor or transformer feeder circuits where you need to coordinate with downstream devices without oversizing the breaker. Three poles means it switches all three phases in a single enclosure, standard for 3-phase power distribution in industrial panels.
The TMA trip unit is front-accessible for adjustment without removing the breaker from the panel — helpful when you're commissioning a line and need to dial in the overload setting against the actual motor FLA.