Take care over BWMS power supplies, professor warns
Retrofits involving high-power electronic systems, such as ballast water management systems (BWMSs), should take account of potential electromagnetic compatibility (EMC) problems, warned Frank Leferink, professor of EMC at University of Twente in the Netherlands and technical authority on EMC for Thales Nederland.
In an exclusive assessment of these concerns prepared for BWTT and summarised here, Prof Leferink said that electronic equipment such as power electronics for energy-efficient lighting, electric propulsion and BWMSs consume power in a pulsed manner, which is completely different from conventional power supply systems, which were designed for mostly linear loads with a power factor (PF) different from unity.
“Modern electronic loads consume pulsed currents, with a high peak current with respect to effective current and, if continuous, a high total harmonic distortion of the current (THDi).” Because the power supply system on a ship has a high internal impedance, the THDi results in a high total harmonic distortion of the voltages (THDv), which can cause problems with sensitive electronic equipment such as navigation, communication and automation equipment and reduce accuracy in measuring equipment.
“All classification societies are extremely concerned about harmonic voltage distortion and the possible consequences should some critical item of equipment malfunction or fail,” Prof Leferink said, and they impose strict limitations on the magnitude of harmonic voltage distortion.
Due to space restrictions with BWMS and other retrofits, cheaper and smaller systems are often selected without active PF circuits and sufficient filtering, causing many severe problems later on, he said. In BWMSs that use UV lamps, “the applied electronic lamp drivers with active PF circuits, low mains distortion, filtering for low EMC levels and improved immunity to mains voltage surges will lead to superior performance,” he said. Overvoltage peaks can deteriorate or destroy the lamps in the ballast water system, he added.
Using proper power systems can also achieve significant cost savings through reduced energy demand, lower operating temperatures and extended electrical equipment life. (Source: http://www.ballastwatermanagement.co.uk)