Purchase now: Allen Bradley 1746-P3 DC Power Supply
Purchase now: Atlantechdrives provides you the 1746-P3, a specialized, high-performance DC-to-DC power supply designed by Allen Bradley for the renowned SLC 500 automation architecture. While the majority of control panels operate on AC line voltage, the 1746-P3 is engineered exclusively for systems that run on a 24V DC power grid. This makes it an absolute necessity for remote terminal units (RTUs), solar-powered pumping stations, mobile industrial equipment, and facilities with centralized battery backup systems. The module seamlessly converts the incoming 24V DC control voltage into the highly regulated 5V DC and 24V DC backplane currents required to power the SLC processor and its associated I/O modules.
Technical Specifications of the 1746-P3
The 1746-P3 mounts securely on the left side of any 1746 expansion chassis (4, 7, 10, or 13-slot). It features integrated electrical isolation and overcurrent protection to safeguard the delicate backplane electronics from voltage spikes commonly found in DC battery charging circuits.
- Part Number: 1746-P3
- Component Type: DC System Power Supply
- Compatible System: Allen Bradley SLC 500
- Input Voltage Range: 19.2 to 28.8V DC
- Backplane Output Capacity (5V DC): 3.6 Amps
- Backplane Output Capacity (24V DC): 0.87 Amps
- Inrush Current: 20 Amps maximum
- Isolation: Field wiring to backplane isolation
Expert Installation Advice: Input Voltage Drops and Wire Gauge
When installing a DC-input power supply, wire gauge is far more critical than with AC supplies. Expert Tip: The 1746-P3 can draw significant continuous current from your 24V DC source, and up to 20 Amps of inrush current during startup. If you use thin wire or run the cable over a long distance from the main DC power plant to the PLC cabinet, the resistance of the wire will cause a «voltage drop.» If the voltage dips below 19.2V DC during startup or peak operation, the power supply will fail to initialize or unexpectedly drop the backplane power, crashing the processor. Always use heavy-gauge copper wire (minimum 14 AWG) and keep DC power runs as short as possible to ensure the supply receives a stable 24 Volts.
Maintenance: The «User Power» Difference
A common troubleshooting point for engineers switching from an AC supply (like the P1 or P2) to the DC-powered 1746-P3 is the lack of «User Power.» The AC models provide a small terminal block that outputs 24V DC to power external sensors. The 1746-P3 does not provide external user power. You must power all your field devices, proximity switches, and DC output modules directly from your main external 24V DC grid. Attempting to draw external power from this unit is impossible and requires proper panel planning.
Frequently Asked Questions (FAQs)
Q: What happens if I reverse the polarity on the input terminals?
A: The 1746-P3 features internal reverse polarity protection. The unit will not power up, but it generally will not suffer catastrophic damage. Simply turn off the power, correct the wiring (+24V to DC+ and 0V to DC-), and reapply power.
Q: Can the 1746-P3 power a fully loaded 13-slot chassis?
A: It depends entirely on the modules you select. With 3.6 Amps of 5V DC capacity, it handles most standard digital racks easily. However, if you use many high-density analog modules or network scanners, you must perform a power budget calculation. If you exceed 3.6A, the chassis will fault.
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This 24V DC input power supply is required for mobile or battery-backed SLC systems using the 1746-A7 chassis.
