Polyphase wireless power transfer systems, coil assemblies and resonant networks
Polyphase wireless power transfer systems are provided. The transfer system may be used for charging hybrid and electric vehicles. The systems are capable of transferring over 50 KW over an air gap of 15 cm. The systems use a rotating magnetic field to transfer power. The system may comprise transmitter coil assembly. The coil assembly may be one or more layers. The system may employ either unipolar or bipolar coils. The transmitter also comprises compensating capacitance connected in series with at least one coil for each phase. A value of the compensating capacitance for each phase is determined such that the transmitter has at least two independently excitable resonant modes at a resonant frequency. The transmitter is compatible with a plurality of different receivers including three-phase, single phase with a circular coil and single phase with DD coils.
1 . A double layer bipolar polyphase coil assembly comprising:
a ferrite; and
two coils for each of polyphase, the two coils having an opposite polarity, wherein the two coils for the same phase of a respective polyphase are in different layers, coils for the same phase that have opposite polarity are not aligned in a stacked direction, and a distance between the ferrite and each layer is different,
wherein connections to a compensation network are co-planar with a respective layer.
2 . The double layer bipolar polyphase coil assembly of claim 1 , wherein a number of phases in the polyphase is three.
3 . The double layer bipolar polyphase coil assembly of claim 2 , wherein each coil spans 120° of a respective layer.
4 . The double layer bipolar polyphase coil assembly of claim 2 , wherein a center of the two coils for the same phase that have opposite polarity are offset by 180°.
5 . The double layer bipolar polyphase coil assembly of claim 1 , wherein the ferrite is formed by ferrite tiles.
6 . The double layer bipolar polyphase coil assembly of claim 1 , wherein each coil is positioned in a wireguide.
7 . The double layer bipolar polyphase coil assembly of claim 1 , wherein there is a balanced mutual inductance between coils of different phases.
8 . The double layer bipolar polyphase coil assembly of claim 7 , wherein there is a balanced self inductance of the coils of the different phases.
9 . The double layer bipolar polyphase coil assembly of claim 1 , where each coil comprises 6AWG type 2 litz wire.
10 . A polyphase inductive power transfer system comprising:
a transmitter comprising the double layer bipolar polyphase coil assembly of claim 1 ; and
compensating capacitance connected in series with the two coils for each phase, a value of the compensating capacitance for each phase is determined such that the transmitter has at least two independently excitable resonant modes at a resonant frequency.
11 . The polyphase inductive power transfer system of claim 10 , wherein the at least two independently excitable resonant modes comprise α-axis and β-axis modes.
12 . The polyphase inductive power transfer system of claim 11 , wherein a maximum current density and a magnetic flux density in the at least two independently excitable resonant modes is located in a different position with respect to phases of the polyphase.
13 . The polyphase inductive power transfer system of claim 12 , wherein the different position is a rotation.
14 . The polyphase inductive power transfer system of claim 10 , wherein the double layer bipolar polyphase coil assembly further comprises a housing and wherein the ferrite and the double layer are disposed within the housing.
15 . The polyphase inductive power transfer system of claim 10 , wherein the compensating capacitance is incorporated in the compensation network having a topology of a series wye-capacitance-wye inductance.
16 . The polyphase inductive power transfer system of claim 10 , wherein the transmitter is configured to transfer at least 50 kW at a distance of 15 cm between the transmitter and a receiver when the transmitter and the receiver are aligned with respect to a central axis.
17 . The polyphase inductive power transfer system of claim 10 , wherein the transmitter further comprises a wireless interface and a controller, and wherein when the transmitter receives a type of receiver via the wireless interface from the receiver, wherein the controller controls the transmitter based on the received type of receiver.
18 . The polyphase inductive power transfer system of claim 10 , wherein a transfer efficiency of the transmitter is substantially rotationally invariant to a relative rotation of the transmitter and a receiver when the transmitter and receiver are aligned with respect to a central axis.