A plant's Rotork actuators are nameplated 380 V, while the supplying bus voltage sits around 415 V long-term. Operations asked whether this is sustainable. This article compiles the views and recommendations.

The Question

• Actuator nameplate: 380 V
• Supply bus: ~415 V long-term (about 9% high)
• Can it run like this indefinitely?

Collected Views

• Not long-term: equipment that must stay in automatic should not run continuously at high voltage — it harms the motor and control boards; find and fix the voltage cause promptly (the majority view)
• Tolerance: some hold that ±10% is the allowable band; 415 V on a 380 V nameplate (+9.2%) is at the edge
• Exception: if the equipment was designed for 415 V/60 Hz (e.g. original imported units), 415 V is fine — the nameplate and design frequency decide

Risk Analysis

• Motor: higher voltage raises flux, core losses and heating, accelerating insulation ageing
• Control section: switch-mode supplies have limited input ranges; sustained high voltage ages power-board components (echoing the power-board failure case)
• Contactors and SSRs: switching overvoltage shortens contact life

Recommendations

• Measure the actual voltage at the actuator terminals (running and idle) to rule out measurement-point error
• Trace the cause of the high bus: plant transformer tap position and regulation method; adjust taps or add voltage regulation if necessary
• If unresolvable short-term, supply the actuators through stepped-down/stabilized feeders and intensify thermal inspections of their power boards and motors
• Check the nameplate frequency: 380 V/50 Hz and 415 V/60 Hz are different systems — do not conflate them

Takeaway

A sustained 9% overvoltage sits at the edge of most manufacturers' allowances; short-term harmlessness does not mean absent cumulative damage. When a batch of actuators shares the same high bus, treat it as a systemic issue rather than watching unit by unit.

Related reading: Rotork IQ Series: Terminal Wiring, Infrared Setter Commissioning & Troubleshooting