Wireless power transfer has long promised a world without cables, where phones, sensors, implants, and electric devices soak up energy simply by sitting near a transmitting coil. A new study published in Scientific Reports brings that promise into sharper focus by tackling one of the technology’s most stubborn problems: what happens when a single transmitter must serve many receivers at the same time. Researchers led by Pragyan P. Mohanty, Sushree S. Biswal, and Durga P. Kar of Siksha ‘O’ Anusandhan Deemed to be University, together with Satyanarayan Bhuyan of the Indira Gandhi Institute of Technology, have shown that the number of devices a wireless charging system can support is governed by a delicate balance between how many receivers are connected and how much electrical load each one presents.
The core finding is deceptively simple but technically profound. In a magnetic coupling based wireless power transfer system, the power delivered to each individual load falls as the number of receiver loads grows. A transmitter that can comfortably charge one device at full power cannot simply split that power among five, ten, or twenty devices without consequences. The team demonstrates that for any given input power level there exists a critical limit on the number of receivers that can be driven with a predetermined amount of power. Push beyond that limit and the system’s performance degrades, leaving every connected device starved of energy.
What makes the new work distinctive is its focus on what happens at that critical boundary. Rather than treating the maximum receiver count as a hard ceiling, the researchers asked how the load values themselves should be chosen when a system operates right at its limit. Their analysis reveals that there is a unique combination between the number of receiver loads and the load value that must be maintained to enrich the overall efficiency of the system. Any deviation from this optimal load value, once the system is driven at the receiver’s critical limit, results in a deterioration of efficiency. In other words, matching the right loads to the right number of receivers is not optional; it is the key to keeping the whole transfer chain healthy.
To reach these conclusions, the team built an equivalent circuit model of a series-series compensated wireless power transfer system supporting n receivers. Series-series compensation is one of the most widely used topologies in magnetic resonance wireless power transfer because it allows the resonant frequency of the system to remain largely independent of the load under certain conditions. By writing out the circuit equations for a transmitter coil magnetically coupled to multiple receiver coils, each terminated in its own load, the researchers derived closed-form expressions for the two quantities that matter most to system designers: the power delivered to each individual receiver and the overall power transfer efficiency of the multi-receiver system.
The mathematics exposes how the receivers interact with one another through the shared magnetic field. Each receiver coil reflects an impedance back to the transmitter, and those reflected impedances add together, effectively changing the operating conditions seen by the source. As receivers are added, the total reflected load grows, the current drawn from the source changes, and the voltage available across each receiver’s load shifts. The model captures these cross-coupling effects and makes it possible to compute exactly how much power each receiver receives under a so-called similar load situation, in which every receiver presents the same load value to its coil.
From this analysis a clear pattern emerges. For a fixed input power, increasing the number of identical receivers reduces the power available to each one, and the efficiency of the entire system traces out a characteristic curve as the load value is varied. At the critical limit of receiver count, there is one particular load value at which efficiency peaks. Choose loads that are too heavy or too light relative to this optimum, and the system wastes energy, dissipating power in the coils and compensation networks rather than delivering it to the devices that need it. The researchers emphasize that this optimal pairing of receiver number and load value must be respected if a multi-receiver system is to perform at its best.
The theoretical predictions were not left to stand on paper alone. The team corroborated the concept with both simulation and experimental tests, comparing the outputs of the equivalent circuit model against measured results from a physical prototype. The agreement between the simulated and experimental data supports the central claim: that a unique load assortment exists for each critical receiver count, and that deviating from it measurably degrades performance. This combination of analytical derivation, numerical simulation, and bench-top validation gives the findings a level of rigor that should make them immediately useful to engineers designing real charging systems.
The implications extend across the growing landscape of wireless power applications. Consumer charging pads that top up several phones at once, industrial systems that power fleets of sensors on a factory floor, and biomedical setups that energize multiple implanted devices all face the same fundamental constraint: a single transmitter’s energy budget must be divided among competing receivers. The new results provide a design rule for such systems. Instead of adding receivers until performance collapses, a designer can use the critical limit framework to decide how many devices to support and then specify the load impedance each device should present, ensuring the system operates at its efficiency optimum rather than past it.
The study also highlights why load matching deserves the same attention in wireless power transfer that impedance matching has long received in radio frequency engineering. In conventional wired systems, loads are largely independent, and the source can be redesigned to accommodate them. In a magnetically coupled multi-receiver system, by contrast, every load participates in shaping the electromagnetic environment that all the other loads experience. The efficiency of the whole is therefore a collective property, and the researchers’ demonstration that a unique optimal load combination exists for each receiver count turns load assortment into a first-order design parameter rather than an afterthought.
As wireless power transfer moves from novelty to infrastructure, studies of this kind mark the difference between systems that work in the laboratory and systems that work reliably in the field. By mapping out the critical limit on receiver numbers and identifying the optimal load value that must accompany it, the Indian research team has given the field a practical tool for squeezing maximum efficiency out of multi-receiver charging architectures. The work, published open access in Scientific Reports, was supported by equivalent circuit analysis, simulation, and experimental verification, and offers a roadmap for anyone building the cable-free ecosystems of the future, where dozens of devices may share a single invisible source of energy without any of them being left behind.
Subject of Research: Optimal load selection for multi-receiver wireless power transfer systems at the critical receiver limit
Article Title: Appropriate load assortment in multiple receiver WPT system driven at receiver’s critical limit
Article References: Mohanty, P. P., Biswal, S. S., Kar, D. P., & Bhuyan, S. (2026). Appropriate load assortment in multiple receiver WPT system driven at receiver’s critical limit. Scientific Reports. https://doi.org/10.1038/s41598-026-76832-y
Image Credits: AI Generated
DOI: 10.1038/s41598-026-76832-y
Keywords: wireless power transfer, magnetic resonance, multiple receivers, load matching, series-series compensation, power transfer efficiency, equivalent circuit model, critical receiver limit, energy science, electrical engineering, Appropriate, load
