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
First Claim
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.
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Accused Products
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.
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Citations
17 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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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:
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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 RF serving as a model for an electrically-conductive foreign body positioned in series with the primary coil and calculated according to formula;
RF=[2LP/(Δ
t)]·
ln [(Iref·
I0F)/(I1·
I0)],wherein LP is a value of inductance of the primary coil, Δ
t is a length of a pre-determined time interval, I0 and I0F are amplitude or an effective value of a primary current IP before or shortly after interruption of a power feed-in without presence of the foreign body or with presence of the foreign body, and Iref and I1 are values at which an envelope curve or an effective value of the primary current IP 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.- View Dependent Claims (16)
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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:
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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.
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Specification