Description
Key Technical Specifications
| Parameter | Value |
|---|---|
| Part number | 125840-01 |
| Module type | Power Input Module (PIM) for 3500/15 |
| Compatible front module | 3500/15 power supply, P/N 127610-01 |
| Input voltage | 175-264 Vac (high-voltage AC) |
| Voltage/current rating | 250 V, 6.25 A |
| Rack position | Left-side power slot, rear I/O position |
| Redundancy support | Yes, dual 3500/15 supplies in upper/lower slots |
| Hot-swap | Supported when redundant supply is present |
| System compatibility | Bently Nevada 3500 Machinery Protection System |
| Compliance | API 670 machinery protection system component |
| Safety marking | Explosion hazard warning; disconnect power before servicing fuses |
| Condition | Surplus / refurbished; verify revision and physical condition |
Product Introduction
A 3500 rack that loses power after a “like-for-like” swap usually points to one mistake: someone ordered a front power module when the failure was actually on the rear power input side. The 125840-01 is not a standalone power supply. It is the rear Power Input Module for the Bently Nevada 3500/15 power supply assembly, and it mates with the front 3500/15 module — typically P/N 127610-01 — to form a complete AC power supply.
This part is specified for high-voltage AC input, commonly 175-264 Vac, and carries a 250 V / 6.25 A rating. It sits behind the 3500/15 front module in the left-side power slot and is used in 3500/15-02 configurations. In redundant racks, one 3500/15 assembly occupies the upper slot and another occupies the lower slot, so either PIM can be replaced without shutting down the rack — provided the other supply is healthy. Bottom line: confirm whether your rack has 125840-01 or 125840-02 before buying. They are not interchangeable.
QA/QC Transparency SOP
- Intake & Origin Verification — Confirm P/N 125840-01 on the label. Check for burned terminals, cracked connectors, corrosion, or missing fuse holders. Verify it matches the installed 3500/15 front module P/N 127610-01.
- Live Functional Testing – Install the PIM into a verified 3500/15 power assembly and seat it in a live 3500/05 rack. Apply rated AC input and confirm the 3500/15 front module powers up, rack bus voltage is stable, and downstream monitor modules report normal status.
- Electrical Parameter Tests — Verify AC input continuity, insulation resistance, and terminal integrity. Check fuse continuity and rating. Measure output to the 3500/15 assembly under load to confirm stable operation within expected rack power limits.
- Firmware/Config Verification — Confirm the 3500/15 assembly reports normal power status through the 3500/22M TDI or 3500/20 RIM. Verify no power-related alarms persist after seating and energizing.
- Final QC & Anti-Static Packaging — Record test results, label the unit with P/N and test date, bag in ESD packaging, and ship in rigid carton. Surplus units are sold as-tested, not as-new OEM.
Field Engineer Gotchas
- 125840-01 vs 125840-02 is not cosmetic. The -01 is the high-voltage AC PIM (175-264 Vac). The -02 is the low-voltage AC variant. Swapping them without checking the rack configuration can leave the supply dead or damage the assembly.
- It is only half of the power supply. The 125840-01 is the rear I/O module. The front 3500/15 module — usually 127610-01 — must also be present and functional. Ordering the PIM when the front module has failed wastes a shutdown window.
- Redundancy slot position matters. In a dual-supply rack, the upper and lower 3500/15 assemblies are independent. Pulling the wrong side during troubleshooting can remove the only healthy supply.
- Fuse and terminal safety are real. The module carries an explosion-hazard warning and requires power disconnection before fuse service. Do not hot-work the AC input terminals in classified areas.
- Backplane seating faults mimic power failures. A partially seated PIM can cause intermittent rack resets. Reseat firmly and verify the front 3500/15 module locks into place.
BENTLY 125840-01
Application Scenarios
- Steam turbine TSI racks: Supplies 3500 rack power from a 220 Vac UPS or plant AC bus. A failed PIM takes out an entire supply assembly, but redundancy keeps monitors alive if the second 3500/15 is healthy.
- Refinery compressor trains: Dual 3500/15 supplies feed vibration, axial position, and differential expansion monitors. Pain point: maintenance replaces the front module when the rear PIM fuse or connector is the actual fault.
- Power generation auxiliary racks: Older 3500 racks still running 125840-01 PIMs face long lead times. Pain point: procurement orders 125840-02 by mistake because both look identical.
- Brownfield rack refurbishments: Cabinet rewiring introduces wrong AC voltage to the PIM. Pain point: 125840-01 expects high-voltage AC; feeding it low-voltage AC results in no output, not a trip.
FAQ
Is 125840-01 a complete power supply?
No. It is the rear Power Input Module for the 3500/15 power supply. The front 3500/15 module, typically P/N 127610-01, is also required.
What is the difference between 125840-01 and 125840-02?
125840-01 is the high-voltage AC PIM (175-264 Vac). 125840-02 is the low-voltage AC PIM. They are not interchangeable.
Can I replace this module while the rack is powered?
Only if the other 3500/15 supply is healthy and carrying the rack load. Even then, treat the AC input terminals as live and follow hazardous-area rules.
What rack slot does it go into?
Left-side power slot, rear I/O position, behind the 3500/15 front power module.
Will this work with any 3500/15 front module?
It pairs with the 3500/15 high-voltage AC configuration, typically P/N 127610-01. Verify the installed configuration before substitution.
Is surplus stock safe for this part?
It can be, if tested under load in a live 3500 rack. The main failure risks are damaged AC terminals, blown fuses, and backplane connector wear. Always request test documentation.
