Yes, PBZ series can be used as an electronic load. Choose the constant current (CC) mode and set the negative current.
However, please note that the power is limited in the bipolar mode where the output voltage is positive and the output current is negative (operation in the second quadrant) as follows: PBZ20-20: 100 W, PBZ40-10: 180 W, PBZ60-6.7: 200 W, PBZ80-5: 200 W.
To use PBZ series as an electronic load, choose the unipolar mode. In the unipolar mode, the negative voltage is not generated, but the operation as an electronic load (the second-quadrant operation) is available with no power limitation (max. 400 W).
For the details, read the user’s manual – chapter of Basic Features – Operation Modes.