Dynamic Wireless Power Transfer for Moving Vehicles

Background

Tracked vehicles—such as vertical elevators, industrial gantry cranes, monorails, and automated guided vehicles—require a continuous and reliable supply of electrical power to operate vital onboard systems, including lighting, climate control, and control electronics. As modern infrastructure expands vertically and industrial automation accelerates, the demand for efficient, real-time power delivery to moving platforms has grown significantly. Ensuring uninterrupted energy transfer along fixed structural pathways is critical for maintaining operational safety, minimizing system downtime, and supporting the high-duty cycles required in contemporary transit and material-handling environments.

However, conventional methods for delivering power to moving tracked vehicles suffer from significant mechanical and electrical drawbacks. Traditional flexible traveling cables add substantial weight, incur high replacement costs, and introduce severe snagging hazards, particularly in high-rise applications. Alternatively, sliding contact rails experience continuous mechanical friction, leading to rapid physical wear, electrical arcing, and frequent maintenance requirements. While onboard battery storage eliminates physical tethers, it introduces excessive vehicle weight, high capital costs, and operational downtime for recharging. Furthermore, existing inductive wireless power transfer alternatives struggle in these environments because their magnetic fields induce problematic eddy-current losses within the surrounding metallic guide frames and structural pathways.

Technology

This dynamic capacitive power transfer (CPT) system delivers real-time, non-contact electrical power to moving tracked vehicles, such as vertical elevators, monorails, and industrial cranes. Operating between 500 kHz and 1 MHz, the architecture transfers energy across a 25–100 mm airgap via electric field coupling between a stationary metal transmitter track and a compact onboard receiver plate. To complete the circuit, the system uses existing conductive mechanical infrastructure—such as steel suspension cables and rolling guide wheels—as a continuous earth ground return path. The electrical link integrates a ground-side DC/AC inverter, a vehicle-side AC/DC rectifier, and specialized inductive compensation networks (including Series-Series, Series-Parallel, Parallel-Series, and LCL topologies) to cancel coupler reactance and power onboard loads.

This technology is differentiated by its quasi-wireless architecture, which eliminates the mechanical wear, snagging hazards, and excess weight of traditional traveling cables, sliding contacts, and onboard batteries. By utilizing existing structural mechanics for the ground return, it operates with a single-pair plate coupler rather than requiring a dedicated wireless return plate, significantly reducing installation costs and vehicle weight. Furthermore, capacitive coupling avoids the eddy-current losses typical of inductive methods, while the resonant compensation networks ensure stable output regulation and high DC-to-DC efficiencies peaking at 87.3%.

Benefits

• Eliminates the need for flexible traveling cables, sliding contact rails, and heavy onboard battery storage systems
• Reduces mechanical wear, snagging hazards, and replacement costs associated with traditional wired power delivery
• Minimizes onboard vehicle weight and capital costs by utilizing a compact conductive receiver plate
• Simplifies system architecture by using existing grounded mechanical infrastructure as the electrical return path
• Avoids the eddy-current losses typically associated with inductive wireless power transfer methods
• Achieves high power transmission efficiency with peak DC-to-DC efficiency reaching 87.3% and AC-to-AC stage efficiency up to 94.5%
• Maintains stable constant-voltage or constant-current output across dynamically changing load conditions
• Adapts easily to a wide variety of tracked vehicles including vertical elevators, monorails, industrial cranes, and automated guided vehicles

Applications

• Cableless elevator cabin power delivery
• Industrial gantry crane wireless electrification
• Monorail transit contactless power supply
• Automated guided vehicle track charging
• Automated storage shuttle power transfer

Additional info

Fei Lu is an Associate Professor in the Department of Electrical and Computer Engineering at Lehigh University. His areas of research include: Electrical Engineering, Power Electronics, High Voltage DC Power Systems, Semiconductor Device Packaging, Renewable Energy

Assignee: Lehigh University; the patent record also identifies Drexel University as an assignee