The Schneider LA9FF4TKF150D3 is a transformer accessory from the TeSys contactor range, rated 150VA with a primary of 280 V and secondary of 120 V. It steps down control voltage for contactor coils or auxiliary circuits in a panel.
The 150 VA rating tells you the transformer's apparent power capacity — enough to energize a few contactor coils or a small control-circuit load. The 280 V primary and 120 V secondary are fixed taps; verify your panel's line voltage matches before wiring.