Marine Power: Pre-magnetization System

FEATURES

• Virtually eliminates inrush current

• Has been successfully implemented on similar installations

• Is simple and robust, relying on a relatively small pre-magnetization transformer and standard switchgear components.

• Eliminates DC current injection on the medium voltage bus.

• Verifies that the main transformer is healthy before closing the feeder breaker.

AKA’s pre-magnetization system reduces the effects of high inrush currents when power is first applied to the transformer primary. These high inrush current conditions can cause major stress on the power generation systems, even leading to the danger of tripping a generator. Removal of inrush allows the control system to better discriminate between normal and abnormal current. 

In order to limit these current peaks, AKA’s pre-magnetizing system magnetizes the iron core in synchronization with the medium voltage bus prior to connection on all major transformers. Once the medium voltage connection has been made, the pre-magnetization source to the secondary is immediately removed. 

With the use of AKA’s pre-magnetizing system, it is possible to connect large transformers to the bus when only one generator is running. The time taken to reinstate operation after a problem has led to the loss of a bus will be greatly reduced, as it will not be necessary to wait for multiple generators to be sequentially started. It also means that, during normal operations, transformers can be easily connected to the bus without the need to start multiple additional generators.

The pre-magnetization sequence is supervised and also provides an opportunity to assess and determine the health of the transformer and the associated network prior to connection of the primary to the medium voltage bus.