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Abstract-This paper describes the results of experimental testing using a high-speed permanent magnet synchronous machine and its motor drive designed to recover potential energy in mobile gantry crane applications. Rubber-Tired Gantry (RTG) cranes are commonly used in shipping ports around the world to move containers massing up to 40 metric tons. These cranes are mobile and derive their electrical power requirements for the hoist motor from a diesel engine and generator set rather than from the utility system. Because these cranes are independent of the utility system, energy regenerated via the hoist motor as a container is lowered to the ground is typically wasted as heat in dissipator resistors. This paper details the operation and experimental results of a novel long-life flywheel motor and its drive system which can capture the regenerated energy and provide it for subsequent container lifts. Such a flywheel system has proven to significantly reduce fuel usage and diesel engine emissions.

Active Magnetic Bearings (AMBs) are already widely used in rotating machinery and continue to gain popularity due to the ever-present push to higher rotational speeds and decreasing prices of associated electronic components. They offer several advantages over conventional mechanical bearings including non-contact rotor support (thus eliminating mechanical wear and the need for lubricants), ability to tune bearing parameters through software for optimum machine performance, remote monitoring and health diagnostic, etc. In some applications, such as in a vacuum or in aggressive environments, they are often the only viable solution. An electromagnetic actuator, along with a position sensor and control electronics, is a key component of AMBs. While there is a variety of actuator designs described in the literature, most of the AMBs built commercially use heteropolar radial electrical actuators in combination with a dedicated electrically-biased axial actuators. On the contrary, since its inception in 1998, Calnetix Technologies mainly uses homopolar permanent magnet (PM)-biased radial actuators along with a homopolar PM-biased combination radial/axial actuators. In this paper, we provide an overview of the research we have done over the last 15 years in this area focusing on the advantages and disadvantages of this approach and explaining why we have made certain design choices.

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Conventional gas turbine generator sets consist of a high speed turbine coupled to a low speed alternator through a speed reduction gearbox. This is required to maintain the alternator output frequency at 50 Hz or 60Hz, as output frequency is directly proportional to speed. Since power is also directly proportional to speed, the conventional system is bulky and possesses a very large footprint. The advent of solid‐state inverters with their unique ability to efficiently and cost effectively change the alternator output frequency has made it possible to eliminate the need to link the alternator speed to the required 50/60 Hz output frequency. This output can be produced with a high‐speed alternator, eliminating the need for a gearbox and greatly reducing the size, complexity, and weight of the machine by trading speed for torque. A direct drive system in which an alternator is coupled directly to a gas turbine is much more compact and highly efficient and requires much less maintenance. In this paper we will review the design and development of a high‐speed permanent magnet alternator in an advanced cycle gas turbine system for shipboard applications. In addition to the alternator's design features, we will discuss design considerations including electromagnetic design, thermal design and structural design of high speed electrical machines, and review the alternator development including risk mitigation.