IndustrialDriveDataDrive Board & Diagnostic Database
Control Techniques / Nidec high-performance drive service reference

Control Techniques Unidrive SP / Unidrive M service platform

A family-level diagnostic record for Unidrive SP and Unidrive M cases where the search intent is usually a short trip label, a hoist/winder symptom, a feedback instability complaint or a failed control-supply condition.

Record facts

Common search patternUnidrive trip label plus symptom, such as OI.AC, Over Volts, PS.24V or encoder feedback problem
First diagnostic boundaryMotor/output vector path, DC-bus/brake path, control-supply path, or encoder feedback/noise path
Database roleBridge trip-code lookup to machine-level diagnosis for closed-loop industrial applications

Service notes

  • Unidrive applications often involve encoder feedback, option modules and machine control, so a drive-only diagnosis can miss the real fault.
  • OI.AC and Over Volts must be classified by timing and load condition before electronics replacement is proposed.
  • PS.24V trips require external 24 V loads, option modules and terminal wiring to be checked before the internal supply is blamed.
  • Feedback instability on hoists and winders may be a cable shielding, encoder supply, grounding or option-module issue rather than a power stack failure.

Related technical records

OI.AC
AC Output Overcurrent Trip

Unidrive SP or Unidrive M trips on OI.AC during enable, acceleration, load change or unstable closed-loop operation.

Open →Over Volts
DC Bus Overvoltage Trip

Unidrive trips on Over Volts during deceleration, hoist lowering, winder stop or high line condition.

Open →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.

Open →Feedback / encoder instability
Encoder Feedback Noise or Instability

Closed-loop Unidrive application is unstable, trips under load, hunts, overspeeds or reports feedback-related symptoms.

Open →Circuit
Unidrive Output Current, Vector Control and Feedback Path

Routes OI.AC and unstable closed-loop behaviour through motor cable, output bridge, current feedback, brake release, encoder feedback, shielding and tuning context.

Open →Circuit
Unidrive DC Bus and Braking Path

Routes Over Volts evidence through line voltage, DC bus, load regeneration, deceleration ramp, brake resistor, brake chopper and feedback-induced instability.

Open →Circuit
Unidrive Control Supply, Option Module and Feedback Path

Routes PS.24V, thermal feedback and encoder instability through external 24 V loads, option modules, feedback wiring, sensor supply, heatsink feedback and control-board evidence.

Open →Workflow
Unidrive OI.AC Overcurrent Diagnostic Workflow

Unidrive SP/M reports OI.AC or trips during enable, acceleration, load change or closed-loop instability.

Open →Workflow
Unidrive Over Volts Braking and Regeneration Workflow

Unidrive reports Over Volts during deceleration, lowering, stop, winder unwind or unstable closed-loop operation.

Open →Workflow
Unidrive PS.24V / Thermal / Feedback Evidence Workflow

Unidrive reports PS.24V, thermal feedback symptoms, O.ht/O.ht1 or feedback instability with option modules and external control wiring.

Open →