Sulzer looks to do away with marine generator exciter pack failure
Equipment repair specialist Sulzer has been on a mission to find a solution to the problem of exciter pack failure within an ice-breaker’s shaft generator.
The research comes as a result of a recent repair job needed to an ice-breaker and an anchor handling tug which both needed a swift and robust solution to get them back to work quickly.
During the repair work, the damaged components were taken from the receiving port in Aberdeen to Sulzer’s Falkirk Service Center, where they were overhauled and rewound.
However, finding the original cause of the exciter failure led to an investigation into the other component parts of the generator set-up to find a root cause.
Exciter load
Sulzer’s technical design team looked at the evidence and concluded that the failure mode was consistent with a sudden spike in exciter load, which led to catastrophic failure, inter-turn or phase-to-phase.
This was supported with evidence from the commissioning engineer who stated that the only active alarms related to low voltage.
The final conclusion to come from the investigation related to the overcurrent protection offered by the AVR.
At the time of the failure, this was not being utilised and Sulzer advised that this option, and a number of other safeguards, should be implemented on all generators as a means of preventing similar failures in the future.
New resistors
The original AVR manual gave a minimum field resistance of 9Ω, which conflicted with the original installation value of 6.753Ω meaning that the AVR had the potential to become unstable and lose optimum performance.
To resolve the situation, Sulzer provided 2.2Ω resistors that could be fitted in line with the DC exciter field to provide more stable voltage control.
This solution, developed in conjunction with the manufacturer ABB, could be implemented on similar units across the customer’s fleet.
The customer was pleased with the overall project conclusion and the vessel’s chief engineer placed a separate order with the service centre to cover further electrical maintenance once the ship was back at sea.
Visit Sulzer at this year’s Seawork International on stand number SR2.
By Anne-Marie Causer
