Whilst electrical propulsion systems are generally more tolerant of temperature increases, compared to traditional combustion engines, there is an important area where higher temperatures can have a detrimental effect on the performance of the components within a drivetrain.
Tests undertaken by leading manufacturers show that in order to maintain performance and extend the operating life of drivetrain components, temperatures must be kept as low as possible.
A universal principle of electronics says: 10 °C lower temperature will double the life expectancy of electrical components and that is certainly true for electric marine propulsion systems.
However, whilst component lifecycle is of significant importance, there is another issue to consider, which is that in many electric propulsion systems, sophisticated sensor based controls are used to monitor its health and performance. If the water temperature within the cooling circuit rises beyond specified levels, this will be identified by the sensors and power to the drive train reduced to protect the system components. For users, the implications of this switch into ‘limp mode’ could range from simply frustrating, to the downright dangerous, depending on water and weather conditions.
An example of how one company is overcoming this problem is by designing the cooling circuit of their 100 kW drivetrain to operate at a maximum temperature of 60 °C, based on a maximum cooling water intake temperature of 35 °C and by using Bowman heat exchangers to ensure consistent and accurate cooling of all components.
The rapid development and growth of higher powered (60 kW plus) drivetrains has also created the need for more efficient component cooling circuits to manage the heat loads generated and companies are now designing this in to their ranges.
Primary cooling requirements for these systems include the battery pack and on-board charger (where fitted), AC-DC converter, DC-DC converter, plus the electric drive motor itself.
For over 60 years Bowman has worked with the marine industry to provide highly efficient heat exchangers for cooling engine jacket water, engine lubrication systems, turbo intercoolers and transmissions. Bowman’s shell and tube heat exchangers are renowned for their excellent heat transfer performance and long life reliability, especially with challenging cooling media such as sea water.
Now, as the industry moves towards a new era of eco-friendly propulsion, Bowman is again at the forefront of cooling technology and working with both electric and hybrid motive power system manufacturers to provide the levels of system cooling required for their equipment.
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