What the Q64PN powers and what that means for a MELSEC-Q rack
The Q64PN is the 5 VDC rail supply for a MELSEC-Q PLC backplane — it delivers 8.5 A at 5 VDC, which sets the module count you can populate before you hit the current budget. Input is universal: 100 to 240 VAC, 50/60 Hz ±5%, with a wide tolerance of 85 to 264 VAC. That means it handles brownout conditions down to 85 V without dropping the 5 V rail — useful on sites with weak utility feeds. The inrush is clamped at 20 A for 8 ms or less, so you don't need to oversize the upstream MCB just for the power-up surge.
Output protection thresholds — what trips and what holds
Overcurrent protection kicks in at 9.9 A or more — that's about 16% headroom above the 8.5 A rated output, so a brief transient from a module power-up won't nuisance-trip the supply. Overvoltage protection is set at 5.5 to 6.5 V on the 5 V rail. If the regulation loop fails, the supply shuts down before the backplane logic sees damaging voltage. The ERR contact output (24 VDC, 0.5 A) gives a dry signal you can wire into the PLC's diagnostic input or a panel alarm — useful for remote fault annunciation without pulling the main comms bus.