Inductive Power Transfer Systems and Their Future

Inductive power transfer systems are a revolutionary technology that's changing the way we think about energy transfer. They use electromagnetic induction to transfer power wirelessly between two coils, eliminating the need for physical connections.

The first practical inductive power transfer system was developed in 2006 by a team of researchers at the University of Auckland. This breakthrough paved the way for the widespread adoption of inductive power transfer technology.

As the technology continues to advance, we can expect to see even more innovative applications of inductive power transfer. For example, the ability to wirelessly charge electric vehicles is becoming increasingly viable, with some systems already capable of transferring power at rates of up to 3.5 kilowatts.

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Inductive power transfer is a type of wireless power transfer that uses electromagnetic fields to transfer energy between a power source and a receiver.

It's a technology that's already being used in various applications, including electric toothbrushes and smartphones.

Currently, it's mainly used for low-power applications, but it's expected to be utilized in high-power applications for electric vehicles and trains in the near future.

This technology has the potential to revolutionize the way we think about charging our devices and powering our vehicles.

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Inductive power transfer offers several benefits that make it an attractive option for various applications. It eliminates the hassle of plugging and unplugging cables, improving design aesthetics by removing the need for connectors.

Waterproofing is also made possible without the use of specialized waterproof connectors, making it a great solution for devices that need to be used in wet environments. This can be especially useful for devices used in outdoor or aquatic settings.

Switching to inductive power transfer can also reduce waste and contribute to a more sustainable society by enabling prolonged device usage without disposable batteries.

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Magnetic coupling is a widely used method for wireless power transfer, particularly for applications with relatively short distances. It's efficient and stable, making it suitable for various uses like electric toothbrushes and Qi standard devices.

The coupling method, which includes magnetic coupling, has a high efficiency in power transmission and stable transmission, but it's limited to short distances. This is a significant drawback, but it's a trade-off for the benefits it provides.

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Magnetic resonance is another method that uses electrically resonating transmission and reception circuits to induce electric power in the receiver coil. This method is particularly useful for applications that require high power transmission, such as EV charging.

Here are the different wireless power transfer methods, categorized by their attributes:

These representative technologies are the foundation for the various applications and uses of wireless power transfer. By understanding their attributes and limitations, we can better appreciate the benefits and challenges of this technology.

Wireless power transfer offers several benefits over traditional cable-based power transfer. It eliminates the hassle of plugging and unplugging cables.

One major advantage is improved design aesthetics, as it removes the need for connectors. This makes devices look sleeker and more modern.

Wireless power transfer also enables waterproofing without the use of specialized waterproof connectors. This is a significant advantage for devices that are often used in wet or humid environments.

Switching to wireless power transfer can also contribute to a more sustainable society by enabling prolonged device usage without disposable batteries.

An inductive power transfer system uses inductive coupling between two circuits as its basis of operation, essentially a two-part transformer with a primary coil in the power sourcing element and a secondary coil in the item to be charged.

The primary and secondary coils are in the form of coils to increase the magnetic field of the circuits. This setup allows the transmitter coil to generate a magnetic field when current passes through it, which is then coupled to the secondary coil, inducing a voltage when the primary current changes.

The efficiency of an inductive power transfer system is dependent on several factors, including the coupling, or k, between the inductors and their quality factor. The ratio of diameters of the coils, D2/D1, and the distance between coils have a significant impact on the efficiency, with a ratio of less than 0.1 required for high efficiency levels.

Here are some key factors that affect inductive power transfer efficiency:

In-Wheel technology is a type of IPT that's being developed for heavy-duty vehicles like trucks and off-road vehicles.

The ground clearance of these vehicles is typically between 350 and 550 mm, which requires high driving current to transfer significant amounts of power.

High leakage magnetic fields pose a significant concern to the human body, making it a major design challenge.

New MC geometries with leakage flux control are being investigated to address this issue.

One way to maintain the air gap between the transmitter and receiver pads of the MC is to use the wheels as an intermediary stage between the off-board and on-board sides of the vehicle.

The inWIPT system, first mentioned in 2017, involves placing coils in the inner rubber surface of the tire, connected in series with a capacitor and a H-bridge rectifier to form a DC bus.

However, this configuration requires the use of slip rings to transfer the DC bus from the wheel to the on-board side, which has low reliability and high maintenance.

An alternative approach is to place the receiver pad in the inner side of the rim, reducing the air gap between the transmitter and receiver pads, but this requires the use of carbon fiber-reinforced plastic rims, a costlier solution to traditional aluminum rims.

A double coupling in-WIPT system was proposed in 2021 by a research group from University of Coimbra, which avoids the use of slip rings and shields the leakage flux lines above the receiver coils using the aluminum rim.

Inductive power transmission systems use inductive coupling between two circuits as the basis of their operation, effectively making them a two-part transformer.

The primary and secondary coupled circuits are in the form of coils to increase the magnetic field of the circuits. This setup allows the transmitter coil to generate a magnetic field when a current passes through it, which is then coupled to the secondary coil and induces a voltage.

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The voltage induced in the receiver or secondary coil can then be used to drive a battery charger or other circuitry as required. This process relies on the magnetic field generated by the transmitter coil to induce a voltage in the receiver coil.

The efficiency of any inductive power transmission system is dependent upon a number of factors, including the coupling, k between the inductors and their quality factor. Inductor sizes, shape, distance between coils, and coil resistance all play a significant role in determining the efficiency of the system.

A key characteristic of IPT systems is the spatial freedom of the receiver pad towards the transmitter pad due to the vehicle's movement. This movement has a direct impact on the coupling factor, which ranges between 0.05 and 0.3.

To achieve maximum coupling, the inductive coils should be kept very close together, often by using mats onto which the equipment to be charged is placed. This setup allows for maximum efficiency and minimizes the impact of movement on the coupling factor.

The positioning of the receiver pad can be affected by various degrees of freedom, including vertical displacement, lateral displacement, tilt, and rotation. These factors can impact the coupling factor and leakage magnetic fields, making it essential to consider them when designing IPT systems.

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Resonant configurations, such as Series-Series (SS), Series-Parallel (SP), Parallel-Series (PS), and Parallel-Parallel (PP), can be used to compensate for self-inductance and improve the power transfer capabilities of IPT systems. These configurations can be tailored to specific applications, such as high-power or dynamic applications.

Here are some key factors to consider when designing IPT systems:

By understanding these fundamental principles and factors, you can design efficient and effective IPT systems that meet the needs of your specific application.

In the world of transmission basics, one of the most important decisions you'll make is whether to use a track or a pad for your transmitter coil. A track is a continuous power transfer system that offers a constant coupling factor, but it requires higher voltage levels and can be limited by its large inductance.

The choice between a track and a pad ultimately comes down to the specific requirements of your application. If you need a high-power transfer system, a track might be the way to go. However, if you're looking for a more flexible solution that can handle a range of charging positions, a pad might be a better fit.

One key consideration is the impact of the EV movement on the mutual inductance (M12) profile between the transmitter and receiver pads. In DIPT systems, the M12 profile is affected by the lateral displacements between the pads, resulting in a bell-shaped pattern.

Here are some key differences between track and pad systems:

Ultimately, the choice between a track and a pad will depend on the specific needs of your application and the trade-offs you're willing to make. By understanding the pros and cons of each option, you can make an informed decision and choose the best solution for your transmission system.

Inductive power transfer is a technology that allows for the efficient transfer of power between two coils.

The efficiency of inductive power transfer is heavily dependent on the coupling between the coils, which is affected by the ratio of diameters of the coils.

A direct impact on the coupling is made by the ratio of diameters of the coils, D2/D1.

The shape of the coils also plays a role in the level of coupling of magnetic flux.

The distance between the coils has a major effect on the efficiency of inductive power transmission, with efficiency levels of 90% or more only achievable if the distance to coil diameter ratio is less than about 0.1.

Coil resistance causes power to be dissipated as heat, reducing the Q or quality factor of the coils in the system.

Here are some key factors that affect transmission efficiency:

To achieve maximum coupling and efficiency, inductive power transmission systems often incorporate mats onto which the equipment to be charged is placed.

IPT systems are made up of two main components: the off-board and on-board sides. The off-board side typically includes a high-frequency power supply, a resonant compensation network, and the transmitter power pad of a magnetic coupler.

An IPT system's electrical configuration is crucial for efficient power transfer. The system uses two magnetically coupled coils, also known as power pads, to transfer energy between the off-board and on-board sides.

The movement of the receiver power pad in relation to the transmitter power pad due to a vehicle's movement can impact the system's power transfer capabilities. High operating frequencies and resonant compensation networks are used to increase power transfer capabilities and minimize losses.

The free-movement of the receiver pad creates challenges such as vehicle position detection, stray magnetic fields compliance, and foreign object detection between the transmitter and receiver pads.

When developing an IPT (Inductive Power Transfer) system, it's essential to choose the right ICs to ensure efficient and reliable power transfer.

You can try ABLIC's Wireless Power ICs for a seamless experience.

The S-8471/3/4 Series from ABLIC offers a range of ICs for receiver and transmitter control.

The S-8471 Series is a receiver control IC that can be used for various applications.

The S-8473 Series is a receiver control IC with a built-in charge function, which can be useful for powering devices that require a constant charge.

The S-8474 Series is a transmitter control IC that can be used to control the power transfer between the transmitter and receiver.

Here's a quick rundown of ABLIC's Wireless Power ICs:

IPT System Development Areas are crucial for creating efficient and effective IPT systems. The main constituents of IPT systems include electrical configuration of the compensation networks.

Electrical configuration of the compensation networks is a key area of development. Power converters topology is another area that requires careful consideration.

Power converters topology involves the design of the power converters that enable efficient energy transfer. Design optimization of the magnetic coupling structure is also essential for IPT system development.

Design optimization of the magnetic coupling structure is critical for minimizing energy losses and maximizing efficiency.

An IPT system, in its simplest form, uses two magnetically coupled coils, also known as power pads, to transfer energy between the off-board and on-board sides.

The off-board side typically consists of a high-frequency power supply, a resonant compensation network, and the transmitter (Trm) power pad of a magnetic coupler (MC).

The on-board side includes the receiver (Rec) power pad of the MC, a resonant compensation network, the on-board converter, and battery pack.

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An intrinsic characteristic of EV IPT systems is the movement of the Rec pad in relation to the Trm pad due to the vehicle's movement, which affects the coupling factor and system power transfer capabilities.

High operating frequencies together with resonant compensation networks are used to increase power transfer capabilities and minimize losses.

The free movement of the Rec pad creates new challenges like vehicle position detection, stray magnetic fields compliance, and foreign object detection between the Trm and Rec pads.

A two-part transformer is the basis of an IPT system's operation, with the primary contained within the power sourcing element and the secondary contained within the item in which the batteries are to be charged.

The primary and secondary coupled circuits are in the form of coils to increase the magnetic field of the circuits.

The transmitter coil has a current pass through it that generates a magnetic field, which is coupled to the secondary coil and induces a voltage when there is a change in the transmitter primary current.

In a resonant configuration, a capacitor is placed in each side of the power pad coils to compensate for the self-inductance and improve power transfer capabilities.

Four classical resonant configurations can be derived: Series-Series (SS), Series-Parallel (SP), Parallel-Series (PS), and Parallel-Parallel (PP), each with its own intrinsic characteristics and response to coupling, load, and frequency variations.

The SS configuration offers output current independence of load and resonant frequency, making it preferable for high-power applications.

The EDEN system's simplicity and ability to offer true position-free charging on various surfaces are major advantages. Its extremely thin transmitting and receiving pads, which measure less than 0.1 mm, make it compatible with both metallic and non-metallic devices.

Extensive simulations were performed during the EDEN system's development, and one example showed that powering a 15-in. laptop at a 2 mm distance with a 290- × 200-mm receiver pad size provided 160 pF of capacitive coupling.

This capacitive coupling delivered 100 W of power at an efficiency of 88%.

The system's efficiency is impressive, with the potential to deliver around 1700 W/m.