Is a DC bus choke the same thing as a line reactor?

No, they’re very different. The addition of DC bus chokes of significant inductance in 6 pulse AC drives will result in lower harmonic line currents as compared to drives without those chokes. However, the DC bus choke does not guarantee against the possibility of inverter shut down on DC bus over-voltage trips becuase in normal operation the magnetic structure is near saturation. (The inrush current that is delivered to the bus capacitor when a 2000V AC line voltage transient occurs easily saturates the DC choke, resulting in no circuit inductance.) The drive still trips, bus choke or no bus choke. Drives have a bus over-voltage trip mechanism to prevent against high bus voltages seen when the motor tries to regenerate, and to protect the diode bridge from high line-side voltages. Since the bus choke is not positioned in front of the diode bridge, it is unable to protect the drive from the former. A line reactor drops the high frequency transients that cause short DC bus over-voltage conditions, allowing the drive to continue operation through the transient period.