WO2017199114A1 - Magnetic shield for a contactless energy transmission device - Google Patents

Magnetic shield for a contactless energy transmission device Download PDF

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Publication number
WO2017199114A1
WO2017199114A1 PCT/IB2017/052251 IB2017052251W WO2017199114A1 WO 2017199114 A1 WO2017199114 A1 WO 2017199114A1 IB 2017052251 W IB2017052251 W IB 2017052251W WO 2017199114 A1 WO2017199114 A1 WO 2017199114A1
Authority
WO
WIPO (PCT)
Prior art keywords
elements
support
shield
transmission device
ferromagnetic
Prior art date
Application number
PCT/IB2017/052251
Other languages
French (fr)
Inventor
Marcel Jufer
Original Assignee
Mobisystems Sa
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to IB2016052866 priority Critical
Priority to IBPCT/IB2016/052866 priority
Application filed by Mobisystems Sa filed Critical Mobisystems Sa
Publication of WO2017199114A1 publication Critical patent/WO2017199114A1/en

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Classifications

    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00Details of transformers or inductances, in general
    • H01F27/34Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
    • H01F27/36Electric or magnetic shields or screens
    • H01F27/365Magnetic shields or screens

Abstract

The invention relates to a lightweight magnetic shield for a high powered contactless energy transmission device, said shield consisting of a composite material comprising "support" elements and ferromagnetic elements, where the mass made up by the "support" elements is lower than the mass of the ferromagnetic elements which occupy the same volume as that of said "support" elements.

Description

 Magnetic shielding for non-contact energy transmission device

Field of the invention

The invention relates to the transmission of energy without contact, particularly in the field of transport.

State of the art

With high powers, non-contact energy transmission induces magnetic fields that are also high, which may be higher than the standards in force (Fig 1), hence the need to use a magnetic shielding system.

 The magnetic shield must be designed to reduce the magnetic field strength to acceptable values, eg. ex. for a man located near the source of the magnetic field, without however creating excessive losses.

 Solutions of the state of the art resort to protections by metal elements such as sheets or plates (Fig 2).

 With non-ferromagnetic materials (Al, Cu), the protection results from induced currents (eddy currents) whose effect is opposite to the field and thus attenuates it. However, these currents create losses, generally undesirable, which reduce the efficiency and effectiveness of transmission.

 With ferromagnetic materials (Fe, Ni and alloys), it is mainly the high permeability that causes the attenuation of the external field by deflection. Nevertheless, eddy currents also appear. They can however be practically eliminated by a configuration with insulated sheets or with ferrite but in this case it is not possible to make thin elements, ie less than 5 mm, because of the fragility of the material, its mass and the difficulty of fixing it under a vehicle. For a thickness of 5 mm, the size of a plate may not exceed 100 x 100 mm. In this case, it is necessary to make a plate assembly.

There is therefore a need to use a light shielding system. Brief description of the figures:

Fig 1 - Magnetic field created by a coil powered by a current

Fig 2 - Magnetic shielding by a ferrite plate

Fig 3 - Magnetic field created by a current at a distance r

Fig 4 - Representation of the linear flux around a conductor

Fig. 5 - Ferromagnetic screen placed next to a driver

 Fig 6 - Magnetic shielding by lightweight composite structure and integrated geometry

General description of the invention

The present invention is based on the observation that it is possible to obtain a thin magnetic shield, as demonstrated below:

Referring to FIG. 3, the magnetic field H created by the current / is at a distance r:

2nr

 The associated magnetic induction B is then: u 2nr

Referring to FIG. 4, it is possible to deduce the linear flux Φ 'closing around a conductor: φ' = Bdr = ^ 2 -dr = ^ ln

Figure imgf000003_0001

 For :

 / = 400 A

Ssa t = 0.6 T r 2 = 0.15 m to 1 m

In- ~ 2 to 4 e = 0.27 to 0.54 mm

The thickness necessary to ensure sufficient shielding is therefore low, at most a few mm. This is mainly determined by the quality of the material (S sat ).

Another way to demonstrate that the thickness of the shield can be relatively small while remaining effective is presented as follows:

Either a ferromagnetic screen placed opposite a conductor (see Figure 5).

By mirror effect (incident property of the field lines), the distribution of the field lines around the driver is either a circle, a semicircle and two lines. The transition occurs for a radius r d such that the length of a field line in the air is the same for both cases.

Ampere's Law is written for a field line:

 ΗάΙ = I

For a circle: l 2nr

 For a semicircle and two straight lines:

H = -L- nr + 2d

 Transition radius rd:

2nr d = nr d + 2d

 2d

The magnetic induction for r> is:

Β = μ 0 Η =

 nr + 2d

We deduce the flux per unit length over a radius between r d and 4r d :

Figure imgf000004_0001
In the ferromagnetic medium of the screen, there is a maximum of B 0.5T. The corresponding thickness is:

 _ Φι

 Bsat

 For / = 1000 A, we have: e = 0.8 mm.

The invention therefore relates to a lightweight magnetic shielding, of equivalent protection to a thin shield which consists exclusively of a ferromagnetic material.

In this document, "light" means "of less weight than a state of the art shielding which would have an equivalent volume".

More specifically, the magnetic shielding according to the invention consists of a composite material comprising "support" elements and ferromagnetic elements, the mass constituted by the "support" elements being smaller than the mass of the ferromagnetic elements which would occupy the same volume than that of the "support" elements.

Preferably, the support members are made of plastic or formed of fiberglass-epoxy, but any other suitable material may also be used.

The presence of the support elements therefore increases the volume of the shielding, preferably in terms of thickness, which makes it possible to obtain a more robust object with respect to the intended use.

Advantageously, the ferromagnetic elements are powders or fibers.

According to a variant of the invention, the shield forms a vehicle floor element.

In another variant, the shield forms the lateral skirt of a vehicle.

Finally, the shield may be disposed under a floor or a metal frame.

FIG. 6 illustrates an embodiment of the invention in which the shielding is arranged under a metal structure forming p. ex. the floor or metal frame of a vehicle.

It goes without saying that the invention is not limited to this example. It can cover any form and / or structure as defined in the claims.

Claims

claims
Lightweight magnetic shielding for high power non-contact energy transmission device, said shield being made of a composite material comprising "support" elements and ferromagnetic elements, the mass constituted by the "support" elements being less than the mass of ferromagnetic elements that occupy the same volume as that of said "support" elements.
2. Shield according to claim 1 wherein the support elements are made of plastic or formed of glass-epoxy fibers.
3. Shield according to claim 1 or 2 wherein the ferromagnetic elements are powders or fibers.
Shielding according to any one of the preceding claims forming a vehicle floor element.
5. Shield according to any one of claims 1 to 4 forming the side skirt of a vehicle.
6. Shield according to any one of claims 1 to 4 adapted to be arranged under a floor or a metal frame.
7. Shield according to any one of the preceding claims, characterized in that its thickness is greater than 5 mm.
PCT/IB2017/052251 2016-05-17 2017-04-19 Magnetic shield for a contactless energy transmission device WO2017199114A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
IB2016052866 2016-05-17
IBPCT/IB2016/052866 2016-05-17

Publications (1)

Publication Number Publication Date
WO2017199114A1 true WO2017199114A1 (en) 2017-11-23

Family

ID=58800859

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2017/052251 WO2017199114A1 (en) 2016-05-17 2017-04-19 Magnetic shield for a contactless energy transmission device

Country Status (1)

Country Link
WO (1) WO2017199114A1 (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2976152A1 (en) * 2011-05-31 2012-12-07 Renault Sa Magnetic shielding screen for e.g. receiver of contactless charging system of power supply battery of hybrid car, has wall to define upper surface, where screen is made of composite material obtained from polymer and ferrite powder mixture
US20140346815A1 (en) * 2011-12-21 2014-11-27 Thyssenkrupp Steel Europe Ag Magnetic Field Shield for Electromagnetic Fields and Vehicle Having an Integrated Magnetic Field Shield

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2976152A1 (en) * 2011-05-31 2012-12-07 Renault Sa Magnetic shielding screen for e.g. receiver of contactless charging system of power supply battery of hybrid car, has wall to define upper surface, where screen is made of composite material obtained from polymer and ferrite powder mixture
US20140346815A1 (en) * 2011-12-21 2014-11-27 Thyssenkrupp Steel Europe Ag Magnetic Field Shield for Electromagnetic Fields and Vehicle Having an Integrated Magnetic Field Shield

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None

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