Control Techniques / Nidec fault record

PS.24V: 24 V Control Supply Overload / Fault

Unidrive reports PS.24V, loses option/module supply, or drops control logic when external loads are connected.

Precision control-supply fault page10 min read

Scope of this technical record

Routes Unidrive PS.24V searches through external 24 V loads, terminal wiring, sensors, option modules and internal supply boundary before condemning the control board.

Safety boundary

Do not bypass or oversize 24 V protection to keep a machine running. Secure the load and document wiring branches before isolating external control loads.

PS.24V load-isolation image

Unidrive PS 24V external load option module and internal supply route diagram
The image turns PS.24V into a branch-isolation record: external loads first, option modules second, internal supply only after evidence.

Searcher intent coverage

PS.24V pages should behave like an intake checklist for control wiring. The user must prove external loads and option modules before an internal supply claim.

Observed situationDecision neededEvidence that satisfies the search
Trip at power-upHard short or internal supplyExternal branch isolation result
Trip when device actuatesSensor/actuator/cable branchBranch current and cable inspection
Trip after module fittedOption-module loadModule identity and removed-module test

What PS.24V users need

PS.24V is a practical fault because it often sits at the boundary between drive electronics and the machine's control wiring. A shorted sensor, damaged I/O cable, option module fault or external load can pull the rail down and look like an internal drive failure.

The useful answer is not simply '24 V overload'. The page must tell the user how to document what is connected, how to isolate branches, and when the internal supply becomes the leading suspect.

Branch-isolation map

A PS.24V record should be organized by connected load, not by guesswork.

24 V evidence route

Observed patternLikely boundaryEvidence to collectEscalation point
Trips at power-upHard load or internal supply collapseRemove documented external branches and retestInternal supply if rail still collapses unloaded
Trips when sensor/actuator enabledExternal device or cable shortBranch current and cable inspectionRepair field device before drive
Trips after option module fittedModule load or module faultModule identity and result without moduleOption-module repair/replacement
Intermittent with door movementControl harness damagePhoto route and flex evidenceHarness repair before board claim
Rail unstable with no loadsInternal supply/control boardVoltage trend and heat evidenceQualified bench repair

Repair boundary

A PS.24V repair request should include a drawing or photo of all connected 24 V loads, whether the fault clears when external loads are removed, which option modules are installed, and whether the fault follows a particular branch or cable movement.

Only after the external loads and option modules are proven should the internal control-supply board be treated as the repair target. This distinction prevents shipping a healthy drive while the real short remains in the machine wiring.

Field record checklist

  • Drive type/frame and option modules
  • All external 24 V loads connected
  • Whether PS.24V clears with branches isolated
  • Terminal and cable photos
  • Trip timing at power-up, enable or device actuation
  • Voltage behaviour with and without external loads

Technical basis and reference documents

This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.

Unidrive SP / M trip-code referencesControl Techniques / public service references

Used for PS.24V trip-family alignment.

Diagnostic workflow