The A50N2-30-11-51 is a 3-pole NEMA size 2 contactor from the Furnas / Siemens A50 series, rated for 480 V 60 Hz operation. It's a general-purpose power switching device for motor loads and resistive heating banks in industrial control panels.
NEMA size 2 defines the contactor's physical frame and current-carrying capacity — typically rated for motor loads up to about 50 A at 480 V, though the exact AC-3 rating should be verified from the nameplate. The 480 V 60 Hz coil means it pulls in on a 480 V control circuit; verify your control transformer taps before wiring. The 3-pole configuration switches all three phases simultaneously. The 30-11 suffix indicates normally-open and normally-closed auxiliary contact blocks (one N.O. and one N.C. built-in), enough for basic interlocking or status feedback without an add-on block.
This is a panel-mount contactor — no DIN rail base. It bolts directly to a backplate or subpanel. The NEMA size 2 footprint is roughly 4.5 inches wide by 5.5 inches tall; plan for adequate side clearance for arc-chamber venting and wiring access. Use ring terminals sized for the lug capacity (typically #14 to #4 AWG on the power terminals).