Subsubsection Converter Cooling (CCU)
The Converter Cooling cabinet contains the equipment required to remove the heat generated by diodes and IGBTs when the converter is operating. The cubicle contains two circulating pumps (one always in stand-by), a stainless steel plate-type heat exchanger, an expansion tank, a resin deionizing cartridge, stainless steel piping and high pressure hoses.
Deionized water is used as the primary cooling medium. because its low conductivity minimizes corrosion and improves heat transfer, while its purity reduces the accumulation of scale formation.
De-ionized water is circulated by the pump to the cooling pipes and ducts of the high voltage sections. Returning coolant then passes through a the heat exchange and the heat from the de-ionized water is removed by raw water. A three-way thermostatic bypass valve controls the flow of raw water to through the heat exchanger to maintain the coolant temperature at an optimum level.
The coolant pressure, temperature, flow rate and conductivity are closely monitored. A high temperature coolant alarm will sound at 43°C (110° F). If a high conductivity is detected, the coolant is shunted through a resin de-ionizing cartridge until until a satisfactory conductivity level is restored,
