TIDUEZ8 May 2021
As Section 1 explained, isolation and a high-voltage bus monitoring circuit is implemented in the schematics and printed-circuit board (PCB). Hardware that measures isolation resistance and leakage current is built with a temporary isolation breaking circuit.
As Figure 2-6 shows, thin film resistors R3, R4, R5, R6, R7, R9, R10, R11, R12, and R13 are used as a potential divider network switched in the high-voltage positive line, whereas R29, R30, R31, R32, R28, R22, R23, R24, R25, and R20 are switched in the high-voltage negative line. Thin film resistors are chosen to have less tolerance, high reliability, and a low temperature coefficient of resistance (TCR). Any deviation in resistor values has an impact on the error of interlock leakage current and isolation resistance calculations.
DC fast chargers supply power to the 400-V battery management system bypassing the onboard battery charger. Conversely, in string inverters, DC lines coming from the PV string panels go up to 1 kV. The current allowed through the resistive bridge determines the delay time in the isolated voltage. Further details are found in Section 1.2.