The EMPF is currently working on a project sponsored by NAVSEA titled “Advanced R&D for Navy Integrated Power Systems (IPS)” that focuses on a series of advanced power electronics hardware devices. These devices are being evaluated for their performance to determine the effectiveness of these new technologies for direct use in high power Navy applications. To evaluate these new advanced technologies, the project is broken down into three major subtasks: fiber optic and advanced sensors, wide band gap (WBG) devices, and advanced heat exchangers. These new advanced technologies have the potential to increase system reliability, increase power densities and improve system performance monitoring. The objective is to validate these alternative technologies in suitable demonstration vehicles capable of providing typical IPS environmental extremes. Upon demonstrating the effectiveness of these technologies versus the current standard, The EMPF will assist with the implementation of these technologies within the Navy DDG 1000 IPS systems.
Task 1: Fiber Optic Sensors
Current sensor technologies are incapable of providing the depth of data necessary for today’s advanced power electronics. Fiber optic and advanced sensors presently available offer several advantages over conventional sensors:
- Higher Accuracy
- Higher Resolution
- Higher Sensitivity
- Lighter Weight
- Smaller Size
Fiber Optic Sensors (FOS) are immune to Electromagnetic Interference (EMI) and can operate in hazardous environments such as temperatures as high as 300°C, or pressures to 20,000 psi. Moreover, a single fiber sensor can operate in dual use, measuring both temperature and pressure.
The objective of the FOS task is to develop a conceptual design of a fiber optic and advanced sensor system (FOSS) utilizing these technologies to more accurately and reliably monitor the health and status of the onboard electric power systems. The EMPF is currently evaluating a number of advanced FOS and Radio Frequency (RF) sensor technologies. These have been installed in DDG1000 switchgear at the Land Based Test Site (LBTS) located at the Naval Surface Warfare Center (NSWC) – Philadelphia. After taking data to assess the benefits of specific placement and establish that the sensors present no increased hazards to existing systems, the sensors will undergo adverse condition testing.
By lowering alarm threshold levels, the repeated ability to observe and record sensor alarms will be established. The operational thresholds will be determined by exceeding operational limits in a controlled and monitored environment.
In addition, these sensor outputs will be tied into the Integrated Condition Assessment System (ICAS) for ship wide Condition Based Maintenance (CBM). An open architecture standard is being developed to enable different manufacturers’ sensors to operate within and independently of the power system.
Task 2: Wide Band Gap Devices
 Another task integral to the IPS project is the study of advanced wide band gap power electronic devices and their direct application within the different IPS topologies. Today’s power system development demands that electronics demonstrate the ability to operate at higher temperatures, frequencies and power densities. The benefits of these demands are reduced cooling requirements, smaller magnetics, reduced system weight and improved efficiency. To help meet these demands, The EMPF is studying the different power conversion hardware and power requirements within the IPS architecture and assessing the potential for applying wide band gap devices to those applications. This includes identifying the potential advantages and disadvantages for each application and a transition plan for implementing the devices. The EMPF is modeling IGBTs and SiC VJFETs in the current electrical system. According to results of the theoretical model, the saturation current of the IGBT was almost 50 times larger than the saturation current of the SiC VJFET. Therefore, a single IGBT is capable of producing significantly more current than a single SiC VJFET. However, the transient time for the SiC VJFET is over 200 times faster than the transient time for the IGBT. Hence, the SiC VJFET will change faster and will drive other devices more quickly than the IGBT. The power dissipation of the SiC VJFET is also 25 times less than the power dissipated by the IGBT.
Task 3: Advanced Heat Exchangers
The final task of the IPS project encompasses the assessment of advanced heat exchanger technology within the current Power Electronic Module (PEM) being developed for the DDG 1000 program. There is a need to extract the heat that is generated by the operation of today’s power electronics. Reducing the junction temperatures of electronic devices enables them to operate at higher current densities. Lower operating temperatures also reduce stresses on the device, which leads to improved efficiency and reduced failures.
In order to adequately measure effectiveness in the IPS environment, cold plates are being manufactured with a similar form factor as in the PEM but using different advanced cooling technologies (Figure 5-1). These will be tested side by side in identical environments to compare design effectiveness under identical heat loadings. Heat exchanger technologies being investigated include foamed graphite, micro-channeled copper, copper pin-fin and copper tubing. A variety of thermal interface materials are also being tested including phase change metal alloys, metal foils, and filled thermal pads and greases. This testing will help determine the heat transfer capabilities, heat transfer mechanisms and properties of these advance heat exchanger systems. In addition, the EMPF has already modeled candidates for heat transfer fluids and has selected three for actual testing; water, propylene glycol, and Dynalene HC. At the conclusion of testing, the EMPF will be able to determine the most effective combination of technologies directly applicable to thermal management in a Naval Integrated Power System.
The Navy has plans for advanced and integrated power electronics in future platforms. To fully exploit the electric power available on these new platforms, a fundamental change in how electric power is converted, delivered and managed will be required. The EMPF will utilize its facilities to complete low power testing of the advanced power electronics hardware. For high power testing, the EMPF will partner with NSWC-Philadelphia to utilize the Land Based Test Site (LBTS) facility to complete testing and analyses of these new technologies. Along with increased performance, decreased weight, and higher reliability, benefits to the Navy include reduced system costs, improved maintainability and decreased manpower requirements.
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