Nowadays, wireless power transmission is increasingly emerging as a disruptive technological revolution for industrialists and manufacturers across all sectors. This innovation opens up new perspectives in product design to make:
robots more autonomous,
medical installations more secure, hygienic and efficient,
mobility more convenient, safer, and more ergonomic.
But how do these technologies work? What are their advantages? Their disadvantages? And most importantly, how to choose the right one for your business?
To help you understand the strategic issues related to wireless transmission, here is the outline we propose:
Operating Principle of Wireless Power Transmission (WPT)
Discovered by Michael Faraday and Nikola Tesla in the 19th-20th century, Wireless Power Transmission is based on a simple principle: the electromagnetic wave. This is emitted by a transmitter and then received by a receiver to be converted into electric current.
Today, several variations of this principle exist:
1. WPT by radio waves (or radiofrequency): Electromagnetic waves are sent at high frequency to transmit a signal over long distances. However, the signal weakens with the distance it travels and can cause negative health effects (see European regulations).
2. WPT by microwaves: this technology sends concentrated beams of microwaves, waves of higher frequency than radio waves (generally between 300 MHz and 300 GHz). This process has the same properties as radiofrequency WPT, but magnified.
3. WPT by magnetic coupling: q current flows in a transmitting coil, creating an oscillating magnetic field. When a receiving coil is placed near the emitted magnetic field, an electric current is induced in it. This technology is effective for short-distance energy transfer and commonly used in mobile phone chargers, for example. It preserves the integrity of surrounding goods and people.
There are, however, other non-electromagnetic approaches, such as capacitive or electrostatic coupling. In this case, the technology is based on the transfer of electrons from one metal plate (primary) to another (secondary) when an alternating current is applied. This circulation of electrons causes a rebalancing of the secondary plate, which can be translated into an electric current. This inexpensive system is ideal for transmitting small amounts of power. However, this technique remains minor and is sensitive to electromagnetic interference.
Comparison of the different technologies
Method | Frequency | Range | Efficiency | Advantages | Disadvantages |
Radio waves | 3 kHz - 300 MHz | Large | Low to medium | - Long range - Penetrates obstacles - Flexible positioning | - Low efficiency over long distances - Sensitive to interference - Health risks at high power |
Microwaves | 300 MHz - 300 GHz | Very large | Medium to high | - Very long range - Unidirectional transmission - Efficient for high power | - Requires direct line of sight - Health risks at high power |
Magnetic coupling | 10 kHz - 1 MHz | Short | High | - High efficiency at short distance - No health risks | - Limited range (a few cm to a few m) - Precise alignment needed |
Capacitive coupling | 10 kHz - 10 MHz | Very short | High | - Compact - Low cost - Efficient for low power | - Very limited range (a few mm to a few cm) - Sensitive to interference |
Understanding magnetic coupling WPT, the current reference
As suggested by the table above, magnetic coupling is the most efficient technique at short distances, while being reliable and safe for users. Thus, it proves ideal for eliminating cables in battery charging devices, thereby removing the limitations of using equipment that implements such energy storage devices.
Applications for charging robots in industry (AGV, AMR, and LGV), for example, allow for optimized use of this equipment, which can be charged during downtime without human intervention, making them even more autonomous (or even fully autonomous).
Fleets of electric bikes or scooters no longer need to be manually collected and dispatched. Their chargers can be directly integrated into the docks or other docking stations where they are deposited after use.
Automating the recharging of electric medical furniture notably frees up time for healthcare staff and improves product safety and hygiene.
Focus on optimizing WPT through resonance
Magnetic resonance helps reduce losses related to energy transmission between the transmitting coil and the receiving coil. These losses generate heat in the system. By reducing them, we can thus increase the transmitted power.
Indeed, magnetic resonance allows for optimal transmission efficiency. There are two ways to achieve this: series resonance and parallel resonance. One allows for maximum power transmission, while the other tolerates frequency imperfections (related, for example, to distance or interference).
The ability to combine these two types of resonance results in a high-performance and optimized system.
Conclusion
For your wireless transition projects, be sure to choose a magnetic coupling WPT technology that takes advantage of dual magnetic resonance. This will allow you to benefit from optimal flexibility in using wireless technology and achieve long-term energy savings through an optimized system.
TESC Innovation will be pleased to assist you during this transition.
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