Ronan Dunne

Supervisor: Dr. Maeve DuffyCo Supervisor: Liam Kilmartin

• 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) 4.7 1 630 55 1.44" " " 40 2.16" " " 20 5" " " 10 8

Capacitor (nF) Frequency(Khz) Distance (mm) Secondary Voltage (V pk-pk) 1 630 55 0.88" " 40 1.38" " 20 2.9" " 10 5.28

Frequency(Khz) Distance (mm) Secondary Voltage (V pk-pk) 300 55 0.12

" 40 0.14" 20 0.18 10 0.22

Vs with magnetic material added to core of receiver coil:

Frequency(Khz) Primary Capacitance Secondary Cap (nF) Distance (mm) Secondary Voltage (V pk-pk)

270 30.38 1 55 3.48

" " " 40 5.52

" " " 20 11.1

" " " 10 19.5

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 = 885W

@ 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

ShieldVs with

Copper shieldVs with

double layer55 1.44 1.2 0.88 0.6440 2.16 1.76 1.32 0.8420 5 3.4 2.4 110 8 5.12 4.56 1.2

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.

Maxwell simulations

Magnetic field without ferrite plate Magnetic field with ferrite plate

Conclusion

• 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.

Questions???