Could it be the inability to generate sufficient electricity with diesel engines only? Maybe the level of electricity generation was not sufficient to allow the radar and other equipment to function at maximum capacity? For example, the 054B’s power generation does not even match those of the newest class of French frigate, despite the latter also powered by CODAD and have much smaller displacement.
Most warships don't use IEPS.
For propulsion, it can be diesel, gas turbines or steam boilers. Or any combination.
The electricity usually comes from a separate set of diesel generators (engines)
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Given that the Type-055 has 6 x 5MW diesel generators for future electricity demand, I would be very surprised if the Type-054B doesn't have sufficient electricity capacity for the future.
(For comparison, the Arleigh Burkes only have 3 x 4MW electricity generators)
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I would add the latest French (FDI) Frigate and the Type-054B look very similar in terms of sensors, weapons, propulsion and other capabilities.
Yet the Type-054B is over a thousand tonnes heavier. So what are they doing with the extra displacement, if not adding electricity generators?