Moog's Naval Systems Business Unit has developed a peak sine drive controller that can handle 15 times as much power as its predecessor and is about 500 cubic inches smaller. The new design dramatically increases the amount of available power without increasing controller volume by refining topologies and using new fluid technology.
Jason Weiss, engineering manager for the business unit, told us Moog has previously designed 10kW peak sine drive controllers with low structure-borne vibration noise levels. Building on top of that experience, the unit set out to develop a 150kW peak controller and examined the challenges of increasing the power of the drive topology.
A new peak sine drive controller from Moog can handle 15 times the amount of power and is 500 cubic inches smaller than its predecessor. (Source: Moog Inc.)
Weiss said four areas predominantly impact power density: losses, thermal conductivity, operating temperature, and package volume. To reduce the losses within the controller, a trade study on using silicone carbide (SiC) switching devices in a multilevel configuration was performed. SiC MOSFETs have proven to have lower conduction and switching losses and operate at higher temperatures than silicon MOSFETs and insulated gate bipolar transistors.
Increasing the output voltage to approximately double that of the baseline design helped decrease the output current and reduced filter losses. As a result, the design used a multilevel configuration versus a standard inverter, which would provide for a reduction in voltage stress on the desired switching devices. The overall controller was designed for a system efficiency of 95 percent.
Although we were able to increase our efficiency, we still had to manage 7.5kW of heat. Various cooling and heat management methods were investigated, including natural convection, forced air, liquid cooling, and heat pipes. We considered factors such as weight, heat transfer, conductivity, complexity, cost, and feasibility. The areas providing the most benefit for our application were the water cooling for managing external heat and dielectric fluid to handle the internal heat.
To obtain a better understanding of the dielectric fluid immersion along with the SiC devices, Moog developed a test unit that could house high-power resistors, inductors, the SiC devices, and the drive circuitry. Weiss said that the engineered dielectric fluid has slightly higher conductivity than air, but the main heat transfer method of the fluid is phase changing, or boiling from a liquid into a vapor.
When a liquid boils, it takes energy (called heat of vaporization) to change from a liquid to a gas. During this phase change, the temperature of the liquid remains constant. The second part of the two-phase cycle is condensing. All the heat absorbed by the vapor rises with the vapor and must be transferred to the condenser for the phase change from vapor to liquid again. The liquid cold plate removes the heat from the enclosure to an external heat exchanger. A test unit was developed to understand the effects of the dielectric fluid Novec.
I could also see a scaled-down version of this for use in electric cars. Space and weight constraints are even more severe in electric cars than they are aboard ships. Automakers already have experience with liquid cooling and the coolant could also supply cabin heat, instead of the resistance heating or heat pumps now used with pure electric cars (hybrids still use engine coolant from the internal-combustion engine for cabin heat, of course).
Liquid cooling is more efficient, but also more troublesome to maintain. Note that Moog's Naval Systems is developing this. I can easily see the reduced size being very attractive.
The heat has to go somewhere though, so this liquid system would probably interface with some sort of seawater heat exchanger having its own maintenance difficulites.
I can see this unit being quite self-contained - literally sealed. Uncouple the heat exchanger connections, the line in and load out connections, and the control connection and yank the whole thing if it did fail.
Current technology devices that are air-cooled have replacable modules - only a part of them usually fails (well, hopefully only a part fails).
Don't get me wrong - this is really cool stuff (no pun intended). But it doesn't come without a price.
Al, this is an interesting development in the power electronics field that parallels the ones I have seen in the computing world. Even on high preformance desktop computers liquid cooling is being used. For servers in a data center, the densities have forced that. I read a while back that Verizon and at&t were both specing liquid cooling for their data and switching center.
Are they robots or androids? We're not exactly sure. Each talking, gesturing Geminoid looks exactly like a real individual, starting with their creator, professor Hiroshi Ishiguro of Osaka University in Japan.
For industrial control applications, or even a simple assembly line, that machine can go almost 24/7 without a break. But what happens when the task is a little more complex? That’s where the “smart” machine would come in. The smart machine is one that has some simple (or complex in some cases) processing capability to be able to adapt to changing conditions. Such machines are suited for a host of applications, including automotive, aerospace, defense, medical, computers and electronics, telecommunications, consumer goods, and so on. This discussion will examine what’s possible with smart machines, and what tradeoffs need to be made to implement such a solution.