2-20 BOP HIPWR 1113152.8.2 MULTIPLE UNIT PROTECTIONFor multiple unit configurations it is necessary to configure the protection so that a fault will shutdown all the interconnected power supplies. Figure 2-9 is a simplified diagram showing typicalinterconnections for master/slave configurations.2.8.3 MULTIPLE UNIT SOURCE POWERWhen multiple units are connected in series or parallel, the individual power supplies of the sys-tem may be connected to different phases of a 3-phase a-c power source.FIGURE 2-9. TYPICAL MASTER/SLAVE PROTECTION INTERCONNECTIONSUpon startup, PAR/SER PROT IN PORT pin 8 of the master goes low, and stays low until allslaves are powered up. Normal power up of a unit causes the transistor connecting PAR/SERPROT IN PORT pin 2 and PAR/SER PROT OUT PORT pin 2 to conduct. The transistors of allunits are connected in series, effectively shorting out all the shutdown diodes (the shutdowndiodes of all units are also connected in series) connecting PAR/SER PROT IN PORT pin 1 andPAR/SER PROT OUT PORT pin 1. After all the units are powered up and operating normally,the low at PAR/SER PROT IN PORT pin 8 changes to high, but the conducting transistors keepthe voltage at pin 8 low and the diodes are cut off. If a fault occurs, the transistor between PAR/SER PROT IN PORT pin 2 and PAR/SER PROT OUT PORT pin 2 of the defective unit is cut off,allowing current to flow through the shutdown diodes. This develops internal shutdown signalsthat shut down all units.
