Method for detecting an electrically conductive foreign body in a region of a device for inductively transmitting electrical energy and device for inductively transmitting electrical energy

• US 9,623,763 B2
• Filed: 05/24/2012
• Issued: 04/18/2017
• Est. Priority Date: 05/26/2011
• Status: Active Grant

• Current Assignee: ENRX IPT GmbH
• Original Assignee: Conductix-Wampfler GmbH (Delachaux Group SA)
• Inventors: Wechlin, Mathias, Asselin, Pascal
• Primary Examiner(s): Lee, Eric
• Application Number:
  US14/122,262
• Publication Number:
  US 20140191715A1
• Time in Patent Office: 1,790 Days
• Field of Search: 320108
• CPC Class Codes: B60L 2210/30 AC to DC converters
• CPC Class Codes: B60L 2210/40 DC to AC converters
• CPC Class Codes: B60L 2270/147 electro magnetic [EMI]
• CPC Class Codes: B60L 53/122 Circuits or methods for driving the primary coil, e.g. supplying electric power to the coil
• CPC Class Codes: B60L 53/124 Detection or removal of foreign bodies
• CPC Class Codes: B60L 53/38 specially adapted for charging by inductive energy transfer
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility
• CPC Class Codes: Y02T 90/12 Electric charging stations
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles

Abstract

In a method for detecting an electrically conductive foreign body at a device for inductively transmitting electrical energy from a stationary unit having an electrical power supply unit and a primary inductor to a mobile unit having a secondary inductor and an electric load, electrical power is initially fed from the electrical power supply unit into the primary inductor and the feed-in is interrupted. The curve over time of the resulting decay of an electrical operating variable of the primary inductor is measured and at least one parameter of the measured curve is compared with a corresponding parameter of a reference curve in the event of an interruption of the power feed-in into the primary inductor without the presence of an electrically conductive foreign body. The comparison is used to determine whether an electrically conductive foreign body is present in the region of the magnetic field produced by the primary inductor.

Claims

1. A method for detection of an electrically-conductive foreign body in a magnetic field of a device for inductive transmission of electrical energy from a stationary unit having a power supply unit and a primary coil to a mobile unit having a secondary coil and an electric consumer, the method comprising:

feeding an electrical current from the power supply unit into the primary coil;

interrupting feeding of the electrical current into the primary coil, the interruption causing decay in an electrical-operating magnitude of the primary coil;

measuring progression of the decay over time;

comparing at least one parameter of the measured progression with a corresponding parameter of a reference progression, the reference progression determined by interruption of feeding of the electrical current from the power supply unit into the primary coil in absence of an electrically-conductive foreign body in a region of a magnetic field produced by the primary coil;

establishing whether an electrically-conductive foreign body is present in the region of the magnetic field produced by the primary coil from an amount of decay in the electrical-operating magnitude of the primary coil as compared to an amount of decay shown by the reference progression;

sending a report to a higher unit or to a user of the device if presence of an electrically-conductive foreign body is established, the report indicating the presence of the electrically-conductive foreign body;

determining, in the presence of the electrically-conductive foreign body, an amount of power absorbed by the foreign body during normal operation of the device from the progression of decay over time in the electrical-operating magnitude of the primary coil;

reducing, according to the determined amount of power absorbed by the foreign body, electrical current fed into the primary coil so that power absorbed by the foreign body remains below a pre-determined threshold;

inputting a signal acknowledging a foreign-body effect free state of the device;

repeating steps for detection of an electrically-conductive foreign body; and

sending an error report to the higher unit or to the user of the device if the presence of the electrically-conducive foreign body is repeatedly established, the repeated establishment of the presence of the electrically-conductive foreign body indicating a fault state of the device rather than physical presence of an electrically-conductive foreign body.

2. The method according to claim 1, further comprising confirming presence of the electrically-conductive foreign body when a difference between the parameter of the measured progression and the corresponding parameter of the reference progression exceeds a pre-determined threshold.

3. The method according to claim 1, wherein the at least one parameter of the measured progression is a relative change in an envelope curve of progression over time or is an effective value of a measured electrical operating magnitude within a pre-determined interval of time which begins at or shortly after beginning of the interrupting of feeding of the electrical current.

4. The method according to claim 1, wherein the at least one parameter of the measured progression is length of an interval of time beginning at the interrupting of feeding of the electrical current or shortly thereafter within which an envelope curve of progression over time or an effective value of a measured electrical operating magnitude reaches a pre-determined relative change.

5. The method according to claim 1, wherein the at least one parameter of the measured progression is a value of an ohmic resistance R_F serving as a model for an electrically-conductive foreign body positioned in series with the primary coil and calculated according to formula:

R_F=[2L_P/(Δ

t)]·

ln [(I_ref·

I_0F)/(I₁·

I₀)],

wherein L_P is a value of inductance of the primary coil, Δ

t is a length of a pre-determined time interval, I₀ and I_0F are amplitude or an effective value of a primary current I_P before or shortly after interruption of a power feed-in without presence of the foreign body or with presence of the foreign body, and I_ref and I₁ are values at which an envelope curve or an effective value of the primary current I_P decays within the time interval Δ

t after interruption of the power feed-in without the presence of a foreign body or with the presence of the foreign body.

6. The method according to claim 1, wherein the electrical-operating magnitude is a current I_p through the primary coil or a voltage U_p across the primary coil.

7. The method according to claim 1, wherein, if measurement of the amount of power absorbed by the foreign body during normal operation of the device exceeds a pre-determined threshold, the feeding of the electrical current into the primary coil remains interrupted.

8. The method according to claim 1, further comprising reducing the electrical current fed into the primary coil to a value that is smaller or, at most, equal to a value I_Pmax, which is calculated according to formula:

9. The method according to claim 1, further comprising interrupting delivery of power from the secondary coil to the electric consumer before interrupting feeding of electrical current into the primary coil.

10. The method according to claim 9, wherein the interrupting delivery of power from the secondary coil to the electric consumer is due to short-circuiting of the secondary coil or to breaking of a circuit between the secondary coil and the electric consumer.

11. The method according to claim 1, further comprising producing a resonant electrical circuit without any external excitation by interrupting feeding of the electrical current into the primary coil.

12. The method according to claim 11, wherein progression of the measured electrical-operating magnitude has a form of decaying oscillation of the resonant electrical circuit.

13. The method according to claim 1, further comprising arranging at least one measuring coil adjacent the primary coil to effect measurement of the progression over time of the decay in electrical-operating magnitude caused by interrupting feeding of the electrical current into the primary coil.

14. A device for inductive transmission of electrical energy from a stationary unit having a power supply unit and a primary coil to a mobile unit having a secondary coil and an electric consumer, wherein the device is configured and arranged for execution of the method according to claim 1.

15. A method for detection of an electrically-conductive foreign body in a magnetic field of a device for inductive transmission of electrical energy from a stationary unit having a power supply unit and a primary coil to a mobile unit having a secondary coil and an electric consumer, the method comprising:

feeding an electrical current from the power supply unit into the primary coil;

interrupting feeding of the electrical current into the primary coil, the interruption causing decay in an electrical-operating magnitude of the primary coil;

measuring progression of the decay over time;

comparing at least one parameter of the measured progression with a corresponding parameter of a reference progression, the reference progression determined by interruption of feeding of the electrical current from the power supply unit into the primary coil in absence of an electrically-conductive foreign body in a region of a magnetic field produced by the primary coil;

establishing whether an electrically-conductive foreign body is present in the region of the magnetic field produced by the primary coil from an amount of decay in the electrical-operating magnitude of the primary coil as compared to an amount of decay shown by the reference progression;

determining, in the presence of the electrically-conductive foreign body, an amount of power absorbed by the foreign body during normal operation of the device from the progression of decay over time in the electrical-operating magnitude of the primary coil; and

reducing, according to the determined amount of power absorbed by the foreign body, electrical current fed into the primary coil so that power absorbed by the foreign body remains below a pre-determined threshold;

wherein the at least one parameter of the measured progression is a value of an ohmic resistance R_F serving as a model for an electrically-conductive foreign body positioned in series with the primary coil and calculated according to formula;

R_F=[2L_P/(Δ

t)]·

ln [(I_ref·

I_0F)/(I₁·

I₀)],

wherein L_P is a value of inductance of the primary coil, Δ

t is a length of a pre-determined time interval, I₀ and I_0F are amplitude or an effective value of a primary current I_P before or shortly after interruption of a power feed-in without presence of the foreign body or with presence of the foreign body, and I_ref and I₁ are values at which an envelope curve or an effective value of the primary current I_P decays within the time interval Δ

t after interruption of the power feed-in without the presence of a foreign body or with the presence of the foreign body.

16. A device for inductive transmission of electrical energy from a stationary unit having a power supply unit and a primary coil to a mobile unit having a secondary coil and an electric consumer, wherein the device is configured and arranged for execution of the method according to claim 15.

17. A device for inductive transmission of electrical energy from a stationary unit having a power supply unit and a primary coil to a mobile unit having a secondary coil and an electric consumer, comprising:

means for feeding an electrical current from the power supply unit into the primary coil and for subsequent interruption of this feeding;

means for measuring progression over time of decay of an electrical-operating magnitude of the primary coil caused by interruption of the feeding of electrical current thereto;

means for comparing at least one parameter of the measured progression of decay with a corresponding parameter of a reference progression, the reference progression determined by interruption of feeding of electrical current into the primary coil in absence of an electrically-conductive foreign body in a region of a magnetic field produced by the primary coil;

means for establishing whether an electrically-conductive foreign body is present in the region of the magnetic field produced by the primary coil from an amount of decay in the electrical-operating magnitude of the primary coil as compared to an amount of decay shown by the reference progression;

means for sending a report to a higher unit or to a user of the device if presence of an electrically-conductive foreign body is established, the report indicating the presence of the electrically-conductive foreign body;

means for determining an amount of power absorbed by the foreign body during normal operation of the device from the progression of decay over time in the electrical-operating magnitude of the primary coil;

means for reducing electrical current fed into the primary coil so that power absorbed by the foreign body remains below a pre-determined threshold;

means for inputting a signal acknowledging a foreign-body effect free state of the device;

means for carrying out repeated steps for detection of an electrically-conductive foreign body; and

means for sending an error report to the higher unit or to the user of the device if the presence of the electrically-conducive foreign body is repeatedly established, the repeated establishment of the presence of the electrically-conductive foreign body indicating a fault state of the device rather than physical presence of an electrically-conductive foreign body.