The Eaton A30-30-10-34 is a 3-pole, non-reversing across-the-line contactor rated for 55 A. It carries a 208 V AC coil and one normally open auxiliary contact. This is the sort of part you'd find in a motor starter for a pump or conveyor — switching the line voltage to the motor, with the auxiliary contact feeding a status back to the PLC or lighting a run light on the panel door.
What the 55 A rating means in practice
For motor loads, you'd size it against the full-load amps of the motor — a 55 A contactor handles a motor drawing around 55 A continuous, with some headroom for inrush on startup. The 3-pole construction switches all three phases, which is standard for three-phase motor circuits in North American 208 VAC distribution.
Panel fit and coil voltage
The 208 V AC coil voltage matches common 208Y/120 V commercial and light industrial panels. If your control transformer is putting out 208 V, this contactor pulls in without a separate step-down. The auxiliary contact (1 NO) gives you one feedback signal — enough for a simple run indication or to seal in the start circuit.