QualShips Australia recently completed a complex auxiliary generator excitation system repair involving multiple simultaneous faults across the excitation chain of a Taiyo Electric brushless alternator. The job required off-vessel component rewinding, full component renewal, and hands-on fault tracing to identify a concealed insulation breakdown that had been the underlying root cause throughout.
Initial Fault Condition
The Auxiliary Engine No. 02 alternator was reported with the following defects:
• Burnt exciter stator winding
• Burnt exciter transformer (RT)
• Faulty AVR unit
• Generator unable to build up voltage
Scope of Work
The damaged exciter assembly was removed from the generator and transported to a rewinding facility in Sydney. Upon completion, the rewound exciter was returned onboard and reinstalled. A new exciter transformer (RT) and new AVR unit were procured and installed.
Prior to energisation, insulation resistance tests were conducted on the rewound exciter stator winding and main rotor winding — both returned satisfactory results. The SI1 and SI2 rotating rectifier diode assemblies were inspected and confirmed serviceable. The excitation circuit rheostat was renewed, and all excitation power cabling was fully replaced and re-terminated.
Persistent Fault & Root Cause Identification
Following completion of all installation works, the generator still failed to build up voltage. Several hours of systematic circuit tracing were carried out to investigate the fault.
The root cause was identified as an insulation breakdown at the R phase excitation voltage tapping point, located below the CT unit on the stator winding. This breakdown caused the excitation voltage to leak and short-path to earth instead of feeding through the reactor circuit — preventing voltage build-up on every start attempt. This same defect was also identified as the probable root cause of the original exciter winding failure.
The defective tapping point was repaired, insulation integrity was restored, and the excitation circuit was verified. Parts Supplied & Used
• Rewound exciter (QualShips arranged)
• New AVR unit
• New exciter transformer (RT)
• Excitation power cable (full renewal)
• SI2 diode assembly
Why QualShips
This job illustrates the value of methodical fault tracing on complex brushless alternator systems. Replacing components alone did not resolve the fault — identifying the hidden insulation breakdown at the R phase tapping required hands-on circuit analysis by an experienced marine electrical engineer. QualShips provides attending engineer services across Australian ports and internationally for exactly this type of multi-layer electrical fault.
📞 +61 426 785 085 | 📧 info@qualships.com | 🌐 www.qualships.com
Tags: marine generator repair, auxiliary engine alternator, brushless alternator excitation fault, AVR repair, Taiyo Electric alternator, marine electrical engineer Australia, exciter winding rewind, generator no voltage, marine electrical troubleshooting