Recently, the scale of transport appliances and industrial equipments are getting larger as global industrial and cultural exchange is becoming larger. Especially, when it comes to submarines, it is used in diverse purposes such as tourism and discovering underground resources. And because of the possibility and potential of maritime resources and the drain of the land resources, the value of submarine is gaining much more importance than before. Therefore, in order to response to the change of the worldwide environment and to achieve the competitiveness of our technology, it is necessary to develop an advance submarine by our own. But it is very rare to build up a whole submarine by one company, because the technology of electric propulsion system for the submarines is hold by only a few developed countries. Also the development of this related technology has been lead only by the national institutes, and it is hard to transfer and acquire this technology because of its distinctiveness.
Current domestic submarines are equipped with the electric propulsion system, because space, fuel efficiencies and the speed are important issues for a submarine. It is very important to consider the cooling system, because it stabilizes the operation of the inverter and the electric motor.
These days, domestic submarines cooling system is composed with single of double (dual) cooling system, and mostly use the central fresh water cooling system technology. Also we used the step control and 3-direction valve control of the sea water pump and the fresh water pump to keep the temperature of the fresh water same.
The step control of the sea water and fresh water pump is currently using two steps of control. If the electric motor has a low level of heat or the temperature of the outside sea water gets low and the efficiency of the heat exchanger increases, then overcooling happens inevitably, and the 3-direction valve, which is at the gateway of the fresh water cooling system, controls its conditions to keep the temperature constantly.
The 3-direction valve controls the fresh water flow, which goes into the cooling system, and maintains the fresh water temperature. But this control of the fresh water flow results in an energy loss from the pump.
In this paper, a cooling system of high-power propulsion motor with Energy Saving System (ESS) is described. Normally, the cooling system for ship consists of fresh water pump, sea water pump, 3-way valve and cooler. In the cooling system, F.W(Fresh Water) and S.W(Sea Water) pump are operated on rated rpm, and 3-way valve is controlled to prevent over-cooling. Therefore the power consumption of the pump's motor is changed according to a sea water temperature. In the proposed cooling system, F.W pump and S.W pump are controlled by inverter, and it can reduce the power consumption. We provide simulations results for this novel cooling system.