Description
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Product Introduction
When a critical turbine protection rack drops power mid-run because a single power supply fails, the root cause almost always traces back to a non-redundant PIM that can’t ride through a brief AC line sag.
This half-height rear-slot module is the primary AC power input building block for the 3500 system. It delivers 60W of tightly regulated 24VDC to the rack backplane, and its 2000V RMS isolation barrier blocks line noise that would otherwise corrupt vibration readings on adjacent monitor modules.
125840-02
125840-02
125840-02
125840-02
125840-02
Key Technical Specifications
| Parameter | Value |
|---|---|
| Nominal AC Input Voltage | 110 VAC |
| Full AC Input Range | 85–132 VAC RMS, 120–188 VAC Peak |
| Input Frequency Range | 47–63 Hz |
| Regulated DC Output | 24 VDC |
| Max Continuous Output Power | 60 W |
| Max Output Current | 2.5 A |
| Isolation Voltage | 2000 V RMS |
| Operating Temperature Range | -30°C to +65°C |
| Storage Temperature Range | -40°C to +85°C |
| Non-condensing Humidity Rating | Up to 95% RH |
| Mounting Location | Half-height rear slot of 3500 rack |
| Hot-Swap Support | Full RIUP with redundant paired unit |
Field Application & Technical Pitfalls
This part runs three non-negotiable production-critical roles.
First, it acts as the primary redundant power feed for 3500 racks monitoring 25MW refinery hydrocracker compressors, where a single power loss triggers an automatic full-unit ESD trip.
Second, it delivers isolated clean power for 500MW steam turbine protection systems, blocking VFD line noise that would otherwise cause false high-vibration alarms.
Third, it serves as the backup power input for offshore platform gas turbine safety racks, ensuring no single point of failure can disable machinery protection.
⚠️ Input Voltage Overstress Risk: This module is rated for 132VAC absolute max continuous input. Feed it 240VAC by mistake, and you’ll blow the input rectifier instantly, taking the entire rack offline before the overvoltage protection can trigger.
⚠️ Redundancy Slot Misalignment: The two PIM slots in the rear of the 3500 rack are not interchangeable. If you seat this unit in the lower primary slot without a secondary backup unit installed, the rack will never boot past the power supply health check.
⚠️ Hot-Swap Without Redundancy: If you pull this module out of a single-PIM rack while the system is running, you will drop all power to the entire 3500 chassis immediately. No graceful shutdown, no warning, just full loss of protection.
I watched a senior turbine tech skip the voltage check last winter. He swapped this PIM into a 3500 rack that was accidentally wired to 240VAC from the adjacent lighting circuit. The module blew in 2 seconds, the entire protection rack went dark, and the plant ran for 90 minutes with zero active vibration monitoring while they sourced a replacement unit. That 10-second wiring verification oversight forced the operations team to run the turbine at 60% load the entire shift to reduce risk.
Quality Control (QC) SOP & Transparency
- Inbound Verification: Cross-check the OEM serial number against Bently Nevada’s official part revision database, run anti-counterfeit validation on the module’s laser-etched serial label, and confirm no prior rework traces on the input rectifier solder joints.
- Live Rig Testing: Mount the module in a certified 3500/05 test rack, feed 110VAC nominal input, and verify full 24VDC 2.5A continuous output across 2 hours of 100% load testing.
- Parameter Testing: Perform 2300V AC 60-second dielectric withstand test across the input-to-output isolation barrier, confirm no output voltage drift at 25°C, 50°C, and 65°C, and log all ripple values under full load.
- Final QA & Packaging: Seal the fully tested module in a static-shielding anti-static bag, apply a unique QC passed serial label, and pack it in ESD-dissipative foam with a printed hard copy of the full load test report.
Frequently Asked Questions
- Can I hot-swap this module while the 3500 rack is powered on? Only if you have a second redundant PIM installed in the adjacent rear slot. If you pull it from a single-PIM rack, you will kill all power to the entire chassis instantly.
- What exact 3500 system racks does this part work with? It is fully compatible with all 3500 series racks that accept half-height rear AC power input modules. It will not fit the older 3300 series racks that use a completely different full-height power supply form factor.
- How long is the standard warranty for this new surplus unit? It carries a full 12-month functional warranty. If it fails within that window under specified operating conditions, we cover all return shipping and bench replacement costs.
- How do I tell a genuine OEM unit apart from a refurbished clone? Genuine units have the Bently Nevada hologram sticker on the side of the housing, and the input fuse is a Bently-branded 3A slow-blow part. Refurbished clones use generic fast-blow fuses and skip the official hologram.
- Will this 125840-02 directly replace an older 125840-01 PIM? No. The older -01 variant only supports 47–55Hz input, while this -02 unit extends that to 63Hz. You will need to re-verify the output ripple after swapping to confirm no noise issues on adjacent monitor channels.
- What’s the maximum safe continuous operating temperature at full 60W load? It will hold 24VDC ±1% regulation up to 65°C, though your mileage may vary if the rack cooling airflow drops below 12 CFM and internal component temperatures spike 15°C above ambient.
