Inductive power transfer is a method of transferring power wirelessly from a source to an object requiring power. Inductive coupling - Inductive coupling involves the use of magnetic fields to stimulate the movement of current through a wire Nikola Tesla – Tesla coil. Recent developments in technology Charging Platforms for mobile devices Biomedical applications Advantage: No hazardous, inconvenient cables and wires.
Charging Platform Contains inbuilt transmitter coils which induce a current in the receiver coils in the mobile devices when they are brought close to the platform. Transmitter & receiver coils must be close together as the magnetic fields they produce are small. Bigger the magnetic field, the less efficient it becomes. Improve efficiency - implement resonant circuits in both the Primary and Secondary sides of circuits.
Biomedical applications: The transmitter and receiver coils in these devices are much further apart resulting in low inductive coupling levels. Inductive coupling is used to transfer pulses from the externally worn transmitter to the implanted receiver circuit. These pulses are applied to the relevant nerve endings
Build demonstrator circuit Investigate Electromagnetic shielding techniques Verify calculations and results by applying analytic and finite element analysis techniques
Demonstrator circuit Transmitter and receiver coils Resonance Electromagnetic shielding Calculations (Matlab) & Simulations (Maxwell) Mutual Inductance Inductance of different coils Shielding Effectiveness
Transmitter coil is connected to power source which produces a magnetic field. For a current to be induced, must add a receiver coil inside the transmitter coils magnetic field. receiver coil must be close to the transmitter coil
Built demonstrator circuit which contains transmitter and receiver coils. Capacitors were added to create resonance on the primary and secondary sides which improves power produced. Inductive power transfer was shown by creating enough power to light an LED.
By adding resonance circuits that have the same resonance frequency the current can tunnel from the transmitter to the receiver coil. This improves the efficiency of energy transfer as energy is not scattered in all directions.
Vs increased by 5.06V (pk-pk) Vs without capacitor (w/o resonance): Vs with 1nF capacitor, resonating @ 630Khz: Vs with resonance on both sides: Vs increased by 11.5V(pk-pk) Primary Cap (Nf)Secondary Cap (nF)Frequency(Khz)Distance (mm)Secondary Voltage (V pk-pk) 4.71630551.44 """402.16 """205 """108 Capacitor (nF)Frequency(Khz)Distance (mm)Secondary Voltage (V pk-pk) 1630550.88 ""401.38 ""202.9 ""105.28 Frequency(Khz)Distance (mm)Secondary Voltage (V pk-pk) 300550.12 "400.14 "200.18 100.22 Vs with magnetic material added to core of receiver coil: Frequency(Khz)Primary CapacitanceSecondary Cap (nF)Distance (mm)Secondary Voltage (V pk-pk) 27030.381553.48 """405.52 """2011.1 """1019.5 Vs increased by 2.72V (pk-pk)
Matlab was used to programme formulas and Maxwell was used to simulate results. Mutual Inductance between two planar windings Magnetic field around the winding Formula for Mutual Inductance
Power across diode was calculated in Excel using results measured on oscilloscope. The Following results were calculated: @ Vp = 2V (Pk-Pk) P = 885 W @ Vp = 4V (Pk-Pk) P = 16.3 mW @ Vp = 6V (Pk-Pk) P = 45.0 mW @ Vp = 8V (Pk-Pk) P = 81.9 mW @ Vp = 10V (Pk-Pk) P = 118 mW
EM shielding is the process of limiting the flow of EM fields by using a barrier made to block the magnetic fields. Several tests to compare shielding performance of different materials. No shield Ferrite shield Copper shield Ferrite and Copper shield
Distance (mm) Secondary Voltage (V pk-pk) Vs with ferrite Shield Vs with Copper shield Vs with double layer 551.441.20.880.64 402.161.761.320.84 2053.42.41 1085.124.561.2 SE = 16.48dB
Maxwell used to simulate the effects of different shielding techniques by placing the plates within the magnetic field created by the transmitter coil. Magnetic field without ferrite plateMagnetic field with ferrite plate
The demonstrator circuit clearly shows Inductive power transfer by creating enough power to light an LED. implementing resonance circuits, increases power produced. Adding magnetic material also increases power. Electromagnetic Shielding was used to block magnetic fields. It was proved that a double layer substrate made of copper and ferrite acts as the best shield. Satisfactory results of up to 16.5dbs were produced. Maxwell was used to simulate behaviour of magnetic fields and to verify results.