TRANSFORMER RECTIFIER

During the uncontrolled energisation of transformer,
the large transient current due to flux saturation in
the core, which is called inrush current, can reduce the
transformer’s life due to the high mechanical stresses
involved, and can also lead to the unexpected operation
of protective relays and power quality reduction.
This transient current affects costing time and money as
the engineers have to examine closely the transformer
and the protective system, to check for faults.
The large transient current also causes serious
electromagnetic stress impact and shortens the life of
transformer. The over-voltage resulting from the inrush
current may cause damages to other power apparatus.
FRIEM dedicated engineering to provide a solution to
avoid magnetization peak current during start-up of
main rectifier transformer: the Premag unit.
Concept of premagnetization is to pre-magnetize the
transformer core from an independent source in order
not to have a huge voltage variation at the insertion,
thus limiting the inrush current.
The Premag has a specific design for each transformer
or set of transformers.