Baldor inverter / motor controller model VS1SP420-1B (supports AC V/Hz and Sensorless Vector modes). Input of 480 VAC, 3PH 50/60 Hz; output 480 VAC, 3PH 0-500Hz. Standard Operating zone: 2.5 kHz PWM; Quiet: 5 kHz PWM. Some minor scratches on accompanying manual. New/Surplus, in original packaging.