Off-Resonance Power Transfer for Efficient Air Core Transformers
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Summary
Problems
Existing inductive power transfer systems using air core transformers typically achieve highest efficiency at resonance frequency, but this efficiency can be improved by operating below resonance frequency, especially for high load power applications where alignment and coupling are less critical.
Innovation solutions
A loosely coupled air core transformer system operates at frequencies between 50% to 95% of its resonance frequency, utilizing an AC voltage supply to transmit power to a back EMF generating device, such as a battery, which enhances transfer efficiency by reducing power draw from the primary circuit.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If air core transformer is used instead of ferromagnetic core transformer, then weight and manufacturing cost are reduced, but coupling coefficient deviates significantly from 1.0
Why choose this principle:
The patent changes the operating frequency parameter from the traditional resonance frequency to an off-resonance frequency (specifically, a frequency lower than the resonance frequency). This parameter change allows the air core transformer to achieve both high power transfer and high efficiency without requiring a ferromagnetic core, thus maintaining the weight advantage while improving the effective coupling performance for high load power applications.
Principle concept:
If transformer operates at resonance frequency, then power transfer efficiency is maximized, but power draw from primary circuit increases
Why choose this principle:
The patent changes the operating frequency parameter from the resonance frequency to an off-resonance frequency (lower than resonance frequency). This parameter change creates a new operating point where the transformer achieves high power transfer efficiency to the back EMF generating device while simultaneously reducing the power draw from the primary circuit, thus resolving the contradiction between maximizing efficiency and minimizing power consumption.
Application Domain
Data Source
AI summary:
A loosely coupled air core transformer system operates at frequencies between 50% to 95% of its resonance frequency, utilizing an AC voltage supply to transmit power to a back EMF generating device, such as a battery, which enhances transfer efficiency by reducing power draw from the primary circuit.
Abstract
A power transmission system includes a loosely coupled air core transformer having a resonance frequency determined by a product of inductance and capacitance of a primary circuit including a primary coil. A secondary circuit is configured to have a substantially same product of inductance and capacitance. A back EMF generating device (e.g., a battery), which generates a back EMF with power transfer, is attached to the secondary circuit. Once the load power of the back EMF generating device exceeds a certain threshold level, which depends on the system parameters, the power transfer can be achieved at higher transfer efficiency if performed at an operating frequency less than the resonance frequency, which can be from 50% to 95% of the resonance frequency.