Electrical energy is transferred through magnetic alternating fields from a charging station to the device to be charged without any wire (thus wireless). This technology is commonly used for electric toothbrushes and is now rising in the areas of smartphones and electric vehicles.
Currently, there are two methods:
The Inductive Power Transfer (IPT) uses a primary coil to generate a magnetic oscillating field at the charging station. This field runs through a secondary coil at the device to be charged and induces an alternating current which can be used with a rectifier to recharge a battery.
The Magnetic Resonance Coupling (MRC) is an extension of the inductive power transfer with additional resonant oscillation circuits in between the coils. The effect results in a higher efficiency factor and a higher operating range but in cost of a lower power limit.
Known technologies and standards are Qi, Powermat, Rezence and WiTricity.
| Measurand | Value | Feature | Remarks |
|---|---|---|---|
| electric field strength | 0.39 V/m (simulated) | 85 kHz | phatom is standing perpendicularly behind the vehicle on level with the reception coil; measures of the phantom: 117 cm, 20 kg; sending and receiving coils are aligned [1] |
| electric field strength | 0.4 V/m (simulated) | - | phatom is standing perpendicularly behind the vehicle on level with the reception coil; measures of the phantom: 173 cm, 65 kg; sending and receiving coils are aligned [1] |
| electric field strength | 0.5 V/m (simulated) | 85 kHz | phatom is standing perpendicularly behind the vehicle on level with the reception coil; measures of the phantom: 176 cm, 73 kg; sending and receiving coils are aligned [1] |
| electric field strength | 0.6 V/m (simulated) | 85 kHz | phatom is standing perpendicularly behind the vehicle on level with the reception coil; measures of the phantom: 173 cm, 65 kg; sending and receiving coils are misaligned [1] |
| electric field strength | 0.65 V/m (simulated) | 85 kHz | phatom is standing perpendicularly behind the vehicle on level with the reception coil; measures of the phantom: 117 cm, 20 kg; sending and receiving coils are misaligned [1] |
| electric field strength | 0.8 V/m (simulated) | 85 kHz | phatom is standing perpendicularly behind the vehicle on level with the reception coil; measures of the phantom: 176 cm, 73 kg; sending and receiving coils are misaligned [1] |
| electric field strength | 0.9 V/m (simulated) | 85 kHz | phatom is standing parallely behind the vehicle on level with the reception coil; measures of the phantom: 117 cm, 20 kg; sending and receiving coils are aligned [1] |
| electric field strength | 0.95 V/m (simulated) | 85 kHz | phatom is standing parallely behind the vehicle on level with the reception coil; measures of the phantom: 173 cm, 65 kg; sending and receiving coils are aligned [1] |
| electric field strength | 1.05 V/m (simulated) | 85 kHz | phatom is standing parallely behind the vehicle on level with the reception coil; measures of the phantom: 176 cm, 73 kg; sending and receiving coil are aligned [1] |
| electric field strength | 1.25 V/m (simulated) | 85 kHz | phatom is standing parallely behind the vehicle on level with the reception coil; measures of the phantom: 117 cm, 20 kg; sending and receiving coils are misaligned [1] |
| electric field strength | 1.3 V/m (measured) | 85 kHz | phatom is standing parallely behind the vehicle on level with the reception coil; measures of the phantom: 173 cm, 65 kg; sending and receiving coils are misaligned [1] |
| electric field strength | 1.6 V/m (simulated) | 85 kHz | phatom is standing parallely behind the vehicle on level with the reception coil; measures of the phantom: 176 cm, 73 kg; sending and receiving coils are misaligned [1] |
| electric field strength | 2.4 V/m (mean, simulated) | 85 kHz | peak value from three different body models, standing at the rear side, directly next to the bumper and looking to the car. Power: 7 kW. [2] |
| electric field strength | 2.81 V/m (maximum, simulated) | 85 kHz | Charging system with 3.3 kW power of an electric vehicle with a battery voltage of 400 V. The value is simulated on the skin of an adult male who is lying on his side next to the car (worst case position). [3] |
| electric field strength | 2.83 V/m (maximum, simulated) | 85 kHz | This peak value was simulated when the adult male model was lying besides the car model and has contact between his shoulder and the chassis of the car. Power: 7 kW. [4] |
| electric field strength | 5.95 V/m (maximum, simulated) | 85 kHz | This peak value was simulated when the adult male model was lying besides the car model and holding his arm between the charging coils. Power: 7 kW. [4] |
| magnetic flux density | 1.98–0.03 µT (maximum, measured) | 20 kHz | Measured in 20 cm distance to the coachwork of a golf car which is charged with 1.14 kW. Measurement bandwidth: 9 kHz - 30 MHz. [5] |
| magnetic flux density | 2.48 µT (maximum, simulated) | 85 kHz | Charging system with 3.3 kW power of an electric vehicle with a battery voltage of 400 V. The value is simulated on the skin of an adult male who is lying on his side next to the car (worst case position). [3] |
| magnetic flux density | 4.84 µT (maximum, measured) | 30 kHz | charging system of a Renault Kangoo under a steel chassis. Measurement on the height of the secondary coil under the chassis. Power: 2 kW. [6] |
| Measurand | Value | Feature | Remarks |
|---|---|---|---|
| electric field strength | 0.021 V/m (maximum, measured) | 90 kHz | measures at the location of the greatest maximum inside the bus; measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coil: 95.5 x 82.6 cm [7] |
| electric field strength | 0.026 V/m (maximum, measured) | 70 kHz | at the location of the greatest maximum inside the bus; measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coil: 95.5 x 82.6 cm [7] |
| electric field strength | 0.1 V/m (maximum, measured) | 30 kHz | at the location of the greatest maximum inside the bus; measures of the bus: 6.71 x 2.44 x 2.44; measures of the coil: 95.5 x 82.6 cm [7] |
| electric field strength | 0.109 V/m (maximum, measured) | 50 kHz | at the location of the greatest maximum inside the bus; measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coil: 95.5 x 82.6 cm [7] |
| electric field strength | 0.1892 V/m (measured) | 20 kHz | measured at the back of the bus; measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coils: 95.9 x 82.6 cm [7] |
| electric field strength | 0.1905 V/m (calculated) | 20 kHz | measured in front of the bus; measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coils: 95.5 cm x 82.6 cm [7] |
| electric field strength | 0.196 V/m (measured) | 20 kHz | measured at the left side of the bus; measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coil: 95.5 x 82.6 cm [7] |
| electric field strength | 0.1985 V/m (measured) | 20 kHz | measured on the right side of the bus at level of the coils; measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coil: 95.5 x 82.6 cm [7] |
| electric field strength | 0.2119 V/m (measured) | 20 kHz | measured inside the bus above the coils; measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coils: 95.5 x 82.6 cm [7] |
| electric field strength | 0.545 V/m (maximum, measured) | 10 kHz | at the location of the greatest maximum inside the bus; measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coil: 95.5 x 82.6 xm [7] |
| magnetic flux density | 0.0053 µT (maximum, measured) | 70 kHz | at the location of the greatest maximum inside the bus: measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coil: 95.5 x 82.6 cm [7] |
| magnetic flux density | 0.0081 µT (maximum, measured) | 30 kHz | at the location of the greatest maximum inside the bus; measures of the bus: 6.71 x 2.44 x 2.44; measures of the coil: 95.9 x 82.6 cm [7] |
| magnetic flux density | 0.0191 µT (measured) | 20 kHz | measured at the left side of the bus; measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coil: 95.5 x 82.6 cm [7] |
| magnetic flux density | 0.0193 µT (measured) | 20 kHz | measured in front of the bus; bus measures: 6.71 x 2.44 x 2.44 m; measures of the coil: 95.5 x 82.6 cm [7] |
| magnetic flux density | 0.0194 µT (measured) | 20 kHz | measured inside the bus above the coils; measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coil: 95.9 x 82.6 cm [7] |
| magnetic flux density | 0.0195 µT (measured) | 20 kHz | measured at the right side of the bus at level of the coils; measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coil: 95.5 x .82.6 cm [7] |
| magnetic flux density | 0.0196 µT (measured) | 20 kHz | measured behind the bus; measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coil: 95.9 x 82.6 cm [7] |
| magnetic flux density | 0.03 µT (maximum, measured) | 90 kHz | at the location of the greatest maximum inside the bus: measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coil: 95.5 x 82.6 cm [7] |
| magnetic flux density | 0.23 µT (maximum, measured) | 50 kHz | at the location of the greatest maximum inside the bus; measures of the bus: 6.71 x 2.44 x 2.44 m [7] |
| magnetic flux density | 7.98 µT (maximum, measured) | 10 kHz | at location of the greatest maximum inside the bus; measures of the bus: 6.71 x 2.44 x 2.44 m; measures of the coils: 95.5 x 82.6 cm [7] |
| Measurand | Value | Feature | Remarks |
|---|---|---|---|
| magnetic field strength | 0.4 A/m (simulated) | 6.78 MHz | at a distance of 15 cm centrally over the mobile phone charging station; size of the station: 14.4 x 8 x 0.2 cm³; simulated for 1 W input power [8] |
| magnetic field strength | 1.2 A/m (simulated) | 6.78 MHz | at a distance of 5 cm centrally over the mobile phone charging station; size of the station: 14.4 x 8 x 0.2 cm³; simulated for 1 W input power [8] |
| magnetic field strength | 3.75 A/m (simulated) | 6.78 MHz | at a distance of 5 cm centrally over the mobile phone charging station; size of the station: 14.4 x 8 x 0.2 cm³; simulated for 1 W input power [8] |
| SAR | 30 mW/kg (maximum, simulated) | 6.78 MHz | a standing adult male backwards to a desk with a charging system. Averaged over 10 g tissue. Scaled to 1.34 A of operating current in the transmitter coils. [9] |
| SAR | 42 mW/kg (maximum, simulated) | 6.78 MHz | a sitting adult male in front of a desk with charging systems. Averaged over 10 g tissue. Scaled to 1.34 A of operating current in the transmitter coils. [9] |
| Measurand | Value | Feature | Remarks |
|---|---|---|---|
| electric field strength | 4.5 mV/m | 140kHz | in situ field while charging at the hand; coils positioned at the chest of a body phanthom [10] |
| electric field strength | 5.8 mV/m (simulated) | 140kHz | in situ field while charging at the forearm; coils positioned at the chest of a body phanthom [10] |
| electric field strength | 9.9 mV/m (simulated) | 140kHz | in situ field while charging in the middle of the chest; coils positioned in front of the chest of a body phanthom [10] |
| electric field strength | 25.2 mV/m (simulated) | 140kHz | in situ field between two charging cycles at the forearm; coils positioned at the chest of a body phanthom [10] |
| electric field strength | 29.2 mV/m (simulated) | 140kHz | in situ field between two charging cycles at the hand; coils positioned at the chest of a body phanthom [10] |
| electric field strength | 57.8 mV/m (simulated) | 140kHz | in situ field between two charging cycles in the middle of the chest; coils positioned in front of the chest of a body phanthom [10] |
| magnetic flux density | 4.1 µT (measured) | 5 - 50 kHz | at a horizontal distance of 160 mm to the circular charger pad (diameter: 4.2 m) [11] |
| magnetic flux density | 5.6 µT (simulated) | 5 - 50 kHz | at a horizontal distance of 140 mm to the ciruclar charger pad (diameter: 4.2 m) [11] |
| magnetic flux density | 7.5 µT (simulated) | 5 - 50 kHz | at a horizontal distance of 120 mm to the circular charger pad (diameter: 4.2 m) [11] |
| magnetic flux density | 11.3 µT (simulated) | 5 - 50 kHz | at a horizontal distance of 100 m to the ciruclar charger pad (diameter: 4.2 m) [11] |
| magnetic flux density | 17.8 µT (measured) | 5 - 50 kHz | at a horizontal distance of 80 mm to the circular charger pad (diameter: 4.2 m) [11] |
| magnetic flux density | 30.2 µT (simulated) | 5 - 50 kHz | at a horizontal distance of 60 mm to the circular charger pad (diamter: 4.2 m) [11] |
| magnetic flux density | 57 µT (simulated) | 5 - 50 kHz | at a horizontal distance of 40 mm to the ciruclar charger pad (diameter: 4.2 m) [11] |
| magnetic flux density | 131.3 µT (simulated) | 5 - 50 kHz | at a horizontal distance of 20 mm to the circular charger pad (diameter: 4.2 m) [11] |
| magnetic flux density | 317.5 µT (simulated) | 5 - 50 kHz | at the circular charger pad (diameter: 4.2 m) [11] |
| SAR | 0.35 nW/kg (simulated) | 140kHz | while charging at the hand, averaged over 10 g of tissue; coils positioned at the chest of a body phanthom [10] |
| SAR | 0.62 nW/kg (simulated) | 140kHz | while charging at the forearm, averaged over 10 g of tissue; coils positioned in front of the chest of a body phanthom [10] |
| SAR | 1.1 nW/kg (maximum, simulated) | 140kHz | while charging in the middle of the chest, averaged over 10 g of tissue; coils arranged in front of the the chest of the body phanthom [10] |
| SAR | 13.7 nW/kg (simulated) | 140kHz | between to charging cacles at the hand, averaged over 10 g of tissue; coils positioned at the chest of a body phanthom [10] |
| SAR | 24.9 nW/kg (simulated) | 140kHz | between to charging cycles at the forearm, averaged over 10 g of tissue; coils positioned in front of the chest of a body phanthom [10] |
| SAR | 41.5 nW/kg (simulated) | 140kHz | between two charging cycles in the middle of the chest, averaged over 10 g of tissue; coils arranged in front of the the chest of the body phanthom [10] |
| Measurand | Value | Feature | Remarks |
|---|---|---|---|
| electric field strength | 18 mV/m (maximum, calculated) | 100kHz | analytical and numerical value for center-to-center alignment of the coil; coil diameter: 2.5 m; normalized to 1 A [12] |
| electric field strength | 46 mV/m (maximum, calculated) | 100kHz | analytical and numerical value for Center-to-Center alignment of the coils; coil diameter: 1 m; normalized to 1 A [12] |
| electric field strength | 95–96 mV/m (maximum, calculated) | 100kHz | numerical and analytical value for center-to-center alignment of the coils; coil diamter: 0.25 m; normalized to 1 A [12] |
| electric field strength | 96–97 mV/m (maximum, calculated) | 100kHz | analytical and numerical value for center-to-center alignment of the coils, coil diameter: 0.5 m; normalized to 1 A [12] |
| electric field strength | 180 mV/m (mean, simulated) | 100kHz | vector-averaged value in a body phantom for a coil diameter of 0.25 m; normalized to 1 A [12] |
| electric field strength | 180 mV/m (mean, simulated) | 100kHz | vector-averaged value in a body phantom for a coil diameter of 2 m; normalized to 1 A [12] |
| electric field strength | 190 mV/m (mean, simulated) | 100kHz | vector-averaged value in a body phantom for a coil diameter of 1 m; normalized to 1 A [12] |
| electric field strength | 300 mV/m (mean, simulated) | 100kHz | vector-averaged value in a body phantom for a coil diameter of 0.5 m; normalized to 1 A [12] |
| electric field strength | 380 mV/m (maximum, simulated) | 100kHz | maximum, vector-averaged value in a body phanthom for a coil diameter of 1 m; normalized to 1 A [12] |
| electric field strength | 420 mV/m (maximum, simulated) | 100kHz | maximum, vector-averaged value in a body phanthom for a coil diameter of 2.5 m; normalized to 1 A [12] |
| electric field strength | 500 mV/m (maximum, simulated) | 100kHz | maximum, vector-averaged value in a body phanthom for a coil diameter of 0.25 m; normalized to 1 A [12] |
| electric field strength | 510 mV/m (maximum, simulated) | 100KHz | maximum, vector-averaged value in a body phanthom for a coil diameter of 0.5 m; normalized to 1 A [12] |
| SAR | 23 nW/kg (mean, simulated) | 100kHz | whole body SAR for a body phantom for a coil diameter of 0.25 m; normalized to 1 A [12] |
| SAR | 32 nW/kg (mean, simulated) | 100kHz | whole body SAR for a body phantom for a coil diameter of 2.5 m; normalized to 1 A [12] |
| SAR | 38 nW/kg (mean, simulated) | 100kHz | whole body SAR for a body phantom for a coil diameter of 1 m; normalized to 1 A [12] |
| SAR | 71 nW/kg (mean, simulated) | 100kHz | whole body SAR for a body phantom for a coil diameter of 0.5 m; normalized to 1 A [12] |
| SAR | 73 nW/kg (maximum, simulated) | 100kHz | whole body SAR for a body phantom for a coil diameter of 1 m; normalized to 1 A [12] |
| SAR | 77 nW/kg (maximum, simulated) | 100kHz | whole body SAR for a body phantom for a coil diameter of 2.5 m; normalized to 1 A [12] |
| SAR | 85 nW/kg (maximum, simulated) | 100kHz | whole body SAR for a body phantom for a coil diameter of 0.25 m; normalized to 1 A [12] |
| SAR | 120 nW/kg (maximum, simulated) | 100kHz | whole body SAR for a body phantom for a coil diameter of 0.5 m; normalized to 1 A [12] |
| SAR | 0.3 mW/kg (simulated) | 11.36 MHz | the model (height approc. 170 cm) is located centrally at a distance of 10 cm in front of the transmitting coils; the receiving coils are positioned at a distance of 13.5 cm to the left side; size of the coils: radius: 30.0 cm, width after winding: 20.0 mm, height of coil center (from ground): approx. 115 cm (thorax middle) [13] |
| SAR | 0.4 mW/kg (measured) | 11.92 MHz | the model (height approc. 170 cm) is located centrally at a distance of 10 cm in front of the transmitting coils; the receiving coils are positioned at a distance of 13.5 cm to the left side; size of the coils: radius: 30.0 cm, width after winding: 20.0 mm, height of coil center (from ground): approx. 115 cm (thorax middle) [13] |
| SAR | 0.7 mW/kg (simulated) | 11.36 MHz | the model (height approc. 170 cm) is located centrally at a distance of 5 cm in front of the transmitting coils; the receiving coils are positioned at a distance of 13.5 cm to the left side; size of the coils: radius: 30.0 cm, width after winding: 20.0 mm, height of coil center (from ground): approx. 115 cm (thorax middle) [13] |
| SAR | 0.75 mW/kg (simulated) | 11.36 MHz | the model (height approx. 170 cm) is located centrally at a distance of 1 cm in front of the transmitting coils; the receiving coils are positioned at a distance of 13.5 cm to the left side; size of the coils: radius: 30.0 cm, width after winding: 20.0 mm, height of coil center (from ground): approx. 155 cm (at the height of the armpits) [13] |
| SAR | 1 mW/kg (simulated) | 11.92 MHz | the model (height approx. 170 cm) is located centrally at a distance of 1 cm in front of the transmitting coils; the receiving coils are positioned at a distance of 13.5 cm to the left side; size of the coils: radius: 30.0 cm, width after winding: 20.0 mm, height of coil center (from ground): approx. 155 cm (at the height of the armpits) [13] |
| SAR | 1 mW/kg (simulated) | 11.92 MHz | the model (height approc. 170 cm) is located centrally at a distance of 5 cm in front of the transmitting coils; the receiving coils are positioned at a distance of 13.5 cm to the left side; size of the coils: radius: 30.0 cm, width after winding: 20.0 mm, height of coil center (from ground): approx. 115 cm (thorax middle) [13] |
| SAR | 1.15 mW/kg (simulated) | 11.36 MHz | the model (height approx. 170 cm) is located centrally at a distance of 1 cm in front of the transmitting coils; the receiving coils are positioned at a distance of 13.5 cm to the left side; size of the coils: radius: 30.0 cm, width after winding: 20.0 mm, height of coil center (from ground): approx. 155 cm (at the height of the nose) [13] |
| SAR | 1.55 mW/kg (simulated) | 11.36 MHz | the model (height approx. 170 cm) is located centrally at a distance of 1 cm in front of the transmitting coils; the receiving coils are positioned at a distance of 13.5 cm to the left side; size of the coils: radius: 30.0 cm, width after winding: 20.0 mm, height of coil center (from ground): approx. 95 cm (at the height of the pelvis) [13] |
| SAR | 1.6 mW/kg (simulated) | 11.36 MHz | the model (height approx. 170 cm) is located centrally at a distance of 1 cm in front of the transmitting coils; the receiving coils are positioned at a distance of 13.5 cm to the left side; size of the coils: radius: 30.0 cm, width after winding: 20.0 mm, height of coil center (from ground): approx. 115 cm (thorax middle) [13] |
| SAR | 1.75 mW/kg (simulated) | 11.92 MHz | the model (height approx. 170 cm) is located centrally at a distance of 1 cm in front of the transmitting coils; the receiving coils are positioned at a distance of 13.5 cm to the left side; size of the coils: radius: 30.0 cm, width after winding: 20.0 mm, height of coil center (from ground): approx. 155 cm (at the height of the nose) [13] |
| SAR | 1.85 mW/kg (simulated) | 11.92 MHz | the model (height approx. 170 cm) is located centrally at a distance of 1 cm in front of the transmitting coils; the receiving coils are positioned at a distance of 13.5 cm to the left side; size of the coils: radius: 30.0 cm, width after winding: 20.0 mm, height of coil center (from ground): approx. 95 cm (at the height of the pelvis) [13] |
| SAR | 2.4 mW/kg (simulated) | 11.92 MHz | the model (height approc. 170 cm) is located centrally at a distance of 1 cm in front of the transmitting coils; the receiving coils are positioned at a distance of 13.5 cm to the left side; size of the coils: radius: 30.0 cm, width after winding: 20.0 mm, height of coil center (from ground): approx. 115 cm (thorax middle) [13] |
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