NB360 isolation

How it presents

Symptom

Power Electronics NB360 fails isolation during CableCheck, and because the NB360 cabinet uses a multi-module current-share architecture, technicians must confirm whether the fault traces to a single module's contribution or the shared measurement path before opening the whole cabinet. Cable moisture and single-module contamination are the two leading field causes.

Root causes (by observed frequency)

1. #1 Cable insulation breakdown or moisture on the failing connector path

   Prove with a known-good cable dry-swap before touching any module.

2. #2 A single power module's isolation contribution dragging down the overall cabinet reading

   NB360's multi-module architecture means one contaminated or wet module can fail isolation for the whole bank even if the others are clean.

3. #3 ISO measurement hardware fault on the shared measurement path

   Pursue only after cable and individual module checks are clean.

4. #4 Coolant or condensation ingress at a module quick-connect after service

   Check module service history if the fault started shortly after a repair visit.

Diagnostic procedure

1. 1. Classify whether the fault names a single connector, a single module, or the whole cabinet in the service UI.

   Expected: Fault attributed to a specific connector or module rather than being cabinet-wide by default

   Tools: PE service UI

2. 2. Swap in a known-good cable on the failing connector and retest dry.

   Expected: Fault clears with a dry, known-good cable if the original cable caused it

   Tools: known-good cable

3. 3. Identify which individual module is contributing to the isolation fault using the service menu's per-module readings.

   Expected: One module shows an out-of-spec isolation contribution while others read normal

   Tools: PE service tool

4. 4. Inspect the identified module's quick-connects and enclosure for moisture or coolant residue.

   Expected: No visible moisture or coolant contamination at the module interface

   Tools: flashlight, IR camera

5. 5. Escalate to Power Electronics OEM's module isolation service path if cable and module inspection are both clean.

   Expected: OEM confirms and repairs the specific module or shared measurement fault

   Tools: PE OEM support

The fix

Cable first, then isolate to a single module before swapping the entire bank.

• Cable/gun

  Match connector spec

• Power module

  PE OEM part, ordered per identified module

1. Prove the cable with a known-good, dry swap before assuming any module or the shared measurement path is at fault, since cable moisture remains the single most common cause.
2. Use the service menu's per-module isolation readings to identify exactly which module, if any, is dragging down the cabinet-wide measurement rather than replacing multiple modules speculatively.
3. Inspect the identified module's quick-connects for moisture or coolant contamination, since this is a known cause of single-module isolation faults on NB360's shared architecture.
4. Replace only the specific faulted module through Power Electronics' OEM channel once cable and contamination are ruled out, then validate with a full CableCheck and session before returning the bank to service.