Those high power bipolar devices were very common in ferroresonant UPS devices, as they only needed a simple heatsink about the size of a shoebox to handle 1kVA of power, fed from a 48V battery bank. You also had on there the 2 smaller Semikron SCR half bridges used to charge the battery and provide float voltage control. The only problem was the bipolar blocks were obscenely expensive, and any fault on the driver board meant a blown 400A Dc bus fuse, and one dead transistor block. I took a few apart, the bipolar active device inside is a pair of 1cm diameter disc of silicon, mounted on a aluminia insulator and then bonded to a massive Kovar heat spreader. Leads are thick ribbons for C and E with a thinner set of leads for the base and the emitter sense connections. Later on you had a half meter long heatsink with a lot of parallel 2N3773 transistors on it, using a thin 1mm wire from each emitter as balancing resistors to prevent hotspotting. Fixing was a matter of repairing the driver board, then test it with some 12V lamps in series then getting a box of 100 power devices and a tub of heatsink compound out. One mistake and you have a lot of smoked silicon.