The VW3A7812 is a braking resistor from the Schneider Altivar range, rated at 2.1 Ohm and 75 kW average power at 50 °C. It's an IP23 unit with M10 bar wire connections, sized for high-inertia deceleration or overhauling loads on Altivar drives. The 1140 mm width, 820 mm depth, and 1150 mm height mean it's a floor-standing cabinet resistor, not a panel-mount unit — plan for dedicated floor space and a cable run from the drive's braking terminals.
The 2.1 Ohm value determines the peak braking torque the resistor can absorb — lower resistance draws more current from the DC bus and gives stronger braking, but stresses the drive's braking chopper. The 75 kW average power rating (at 50 °C ambient) tells you the continuous energy dissipation capacity; for intermittent braking duty, the resistor can handle much higher peak power for short periods. Thermal protection is handled via an external thermal overload relay, not built into the resistor itself.
Integration notes
The M10 bar connection is a bolted lug — expect to crimp or weld ring terminals onto your cable, sized for the full braking current. The 1140 x 820 x 1150 mm footprint (W x D x H) requires a floor-standing enclosure or a dedicated compartment; it won't fit on a standard 600 mm deep panel. Ambient storage range is -25 to 65 °C, operating range 0 to 50 °C — if your machine room runs hotter than 50 °C, you'll need to derate the power or add forced ventilation.