Contactless energy transmission system and method for the operation of such a system

Abstract

The invention relates to a contactless energy transmission system, comprising a feed which applies a medium-frequency alternating current to a primary conductor to which at least one secondary coil for supplying at least one consumer is inductively coupled, wherein the feed has a current sensor for detecting the alternating current, wherein the feed has a means for determining a value of the unrest of the peak value of the alternating current, wherein the means is connected to a monitoring means which monitors the value to ascertain whether a permitted degree of deviation from a threshold value is exceeded.

Description

[0001] System for contactless energy transmission and method for operating such a system Description: The invention relates to a system for contactless energy transmission and a method for operating such a system. A system for contactless energy transmission is known from DE 10053373, and in particular Figure 1 thereof, as well as the documents cited therein. Such systems have a feed that impresses a medium-frequency alternating current into an elongated primary conductor. Mobile loads are movable along the primary conductor and have a secondary coil inductively coupled to the primary conductor, by means of which energy can be extracted. In industrial applications, high currents occur, for which the primary conductor must then be designed with a correspondingly large cross-section, which, however, leads to high costs. In addition, high ohmic losses occur. Medium-frequency alternating current is understood here to be an alternating currentwhose frequency is between 10 kHz and 1 MHz. From WO 2006 / 005930 A1, it is known to prevent an arc by means of pulse operation of a system for contactless energy transmission with pulse pauses, which, however, reduces the maximum power that can be transmitted from the feed to the mobile consumers. From DE 102022004254 A1, the closest prior art is a method for inductively transmitting electrical power, wherein the time derivative of the current is monitored and evaluated. The invention is therefore based on the object of increasing environmental protection. According to the invention, the object is achieved in the system according to the features specified in claim 1 and in the method according to the features specified in claim 14. ISI \ EIDOPAT 04.07.2024 Essential features of the invention in the system are that it is provided for contactless energy transmission and comprises a feed,which impresses a medium-frequency alternating current into a primary conductor, to which at least one secondary coil is inductively coupled for supplying at least one consumer, wherein the feed has a current sensor for detecting the alternating current, wherein the feed has a means for determining a value of the unrest, in particular volatility, of the peak value, in particular crest value, of the alternating current, wherein the means is connected to a monitoring means which monitors the value for exceeding a permissible degree of deviation from a threshold value, in particular wherein the monitoring means is designed to display or forward warning information depending on the result of the monitoring and / or to switch off the feed or at least temporarily convert it into pulsed operation.that if an arc occurs – for example, due to a cable break – this dangerous condition is detected by the increased volatility, and therefore a safety-related shutdown or pulsed operation can be implemented. In pulsed operation, the arc is extinguished because the power supply to the arc is temporarily interrupted. The increased volatility can be detected by monitoring the value. The difference between the maximum and minimum values ​​of the peak value of the alternating current can be used as the value. Low-pass filtering reduces the probability of false alarms. The alternating current is preferably detected by the current sensor in such a way thatthat an analog value is provided by the current sensor. After conversion to a digital value, the respective peak value is determined and then a maximum or minimum value is low-pass filtered over time. In this way, a value for disturbance can be determined as the difference between this low-pass filtered, time-sliding maximum value and minimum value and monitored for exceeding a permissible degree of deviation from a predetermined threshold. In this way, when an arc occurs, the large difference between maximum and minimum peak values ​​can be easily and quickly identified, so that safety-related measures can be activated. The advantage of the invention is thatthat no time derivative of the current needs to be calculated, thus requiring little effort, yet still achieving reliable detection of an arc. According to the invention, the respective peak value is determined for each period of the alternating current, and the series of peak values ​​thus determined over time is evaluated with regard to their unsteadiness or volatility. Accordingly, the time derivative is not evaluated, and it is also not monitored whether the time derivative exceeds a threshold. Such steps, i.e., the calculation of the time derivative and the exceeding of a threshold by the time derivative of the current, are optionally addable to the above-mentioned subject matter of the invention. In an advantageous embodiment, the threshold is constant. It is advantageous in this casethat the system can be implemented without any special effort. In an alternative embodiment, the threshold value has different values ​​depending on the operating state of the system, in particular wherein the predetermined threshold value is higher at a first point in time than at a second point in time, in particular at a later point in time, in particular wherein during a period when the feed-in is switched on, in particular at the beginning of the electrical supply of the feed-in by the public AC voltage supply network, the predetermined threshold value is higher than during later operation, in particular continuous operation, of the feed-in. The advantage here is that false alarms can be reduced. This is because in operating states in which large current changes occur,could be confused with the occurrence of an arc. Therefore, adjusting the threshold value enables more stable system operation. In an advantageous embodiment, the value of the disturbance is a temporally determined fluctuation range of the peak values, in particular peak values, of the alternating current. The advantage here is that a simple and fast calculation method can be used. In an alternative embodiment, the value of the disturbance is determined as the difference between - a PT1 and / or low-pass filtered maximum value of the peak values, in particular a temporally determined PT1 and / or low-pass filtered minimum value of the peak values. The advantage here is thatthat individual outliers can be suppressed by means of low-pass filtering. In an advantageous embodiment, the current sensor has an analog-to-digital converter for providing the recorded current values ​​as a digital data stream. The advantage here is that In an advantageous embodiment, the value of the disturbance is determined for each time step as the difference between a maximum value and a minimum value, wherein in each time step, the newly updated maximum value Î_LastMaxFilter is assigned the value of the peak value, in particular the crest value, of the alternating current if this peak value is greater than or equal to the value Î_LastMaxFilterPT1, and otherwise the newly updated maximum value Î_LastMaxFilter is assigned the value Î_LastMaxFilterPT1, which is determined in each time step bythat it is determined as the sum of the value Î_LastMaxFilterPT1 which is one time step older and the difference between the peak value, in particular the crest value, and the value Î_LastMaxFilterPT1 which is one time step older, multiplied by the factor K_T, in particular where the factor K_T is chosen to be much smaller than 1, in particular smaller than one tenth. The advantage here is that the maximum value is determined using a low-pass filter, and thus individual outliers have only an insignificant influence. In an advantageous embodiment, the newly updated minimum value Î_LastMinFilter is assigned the value of the peak value, in particular the crest value, of the alternating current in each time step if this peak value is smaller than or equal to the value Î_LastMinFilterPT1, and otherwise the newly updated minimum value Î_LastMinFilter is assigned the value Î_LastMinFilterPT1, which is determined in each time step bythat it is determined as the sum of the value Î_LastMinFilterPT1, which is one time step older, and the difference between the peak value, in particular the crest value, and the value Î_LastMinFilterPT1, multiplied by the factor K_T. The advantage here is that the minimum value is determined using a low-pass filter, thus ensuring that individual outliers have only a minor influence. In an advantageous embodiment, the feed-in for the event of exceeding the permissible degree of deviation from the specified threshold and subsequent pulsed operation is designed in such a way that a pulse width and / or the amplitude curve of the alternating current can be specified, controlled, or regulated. The advantage here is that environmental protection is increased and costs are reduced because ohmic losses are reduced, thus enabling better utilization of the electrical energy. Furthermore, pulsed operation is advantageous,Because permanent arcing is avoided. When a component or electrical connection is interrupted in the event of a fault or failure, an arc is created that can persist permanently as long as the current is present. However, because there is a pulse width, i.e., no permanent supplying current, the arc is temporarily de-energized. For example, the interruption lasts for a few ms, preferably more than 4 ms. When the power supply is switched back on, i.e., the next current pulse is generated in the primary conductor, the arc can no longer ignite.because the distance at the separated point is too large for the existing voltages. Thus, the pulsed operation also increases the safety of the system. The total energy consumption of the loads can advantageously be transmitted via inductive transmission from the primary conductor. Information can be transmitted separately or by modulating higher-frequency current components onto the primary conductor. Information transmission also takes place, as required, when the primary current disappears. In an advantageous embodiment, the information transmission is additionally synchronized to the zero crossing of the primary current in time periods in which the primary current does not disappear. In an advantageous embodiment, the primary conductor is provided as elongated, in particular with the load being arranged so as to be movable along the primary conductor. The advantage here isthat rail-bound vehicles or vehicles equipped with a track guidance antenna can be supplied without contact. In an advantageous embodiment, the primary conductor is arranged such that the load is rotatably arranged relative to the primary conductor. This is advantageous in that turntables or other rotary axes in systems or machines, such as robots or machine tools, can be supplied. In an advantageous embodiment, the medium frequency is between 9 and 100 kHz. It is advantageous in that electronic power semiconductors, such as IGBTs or MOSFETs, can be used to switch the primary conductor high currents with low losses. This allows for high efficiency. In an advantageous embodiment, the pulse width, pulse width duration, and / or the characteristic time for amplitude modulation, such as the amplitude modulation period, is greater than the period of the medium-frequency current.in particular ten times larger or more. The advantage here is that even with high line inductance, the average available primary current can be adjusted to the needs of the inductively supplied loads. In an advantageous embodiment, the pulse width ratio is matched to the energy buffer and power consumption of the loads. The advantage here is that less current flows than the maximum possible, and thus the ohmic losses are lower. In an advantageous embodiment, the loads with their associated secondary coils are arranged so that they can be moved along the primary conductor. The advantage here is that a contactless supply can be provided for movable loads. In an advantageous embodiment, a line controller is assigned to each primary conductor or sections of the primary conductor. The advantage here is that each line section can be precisely controlled,is adjustable and / or controllable. In an advantageous embodiment, means for data exchange between the feed-in, the line controller and / or the consumer or consumers are included. The advantage here is that data can be transmitted to the feed-in and then taken into account by it. The current in the primary conductor can thus be adjusted to the actual demand. In an advantageous embodiment, the pulse width, the pulse width ratio and / or the amplitude curve of the feed-in can be specified depending on data such as the number of consumers in a section of the line, the amount of energy in the consumer's energy buffer, and the respective power requirement of the consumer. The advantage here is that it is possibleto feed as little current as possible into the primary conductor. In this way, the ohmic losses can be kept to a minimum. Method for operating a system for contactless energy transmission. Essential features of the invention in the method are that medium-frequency alternating current is impressed from a feed into an elongated primary conductor, to which at least one secondary coil for supplying at least one consumer is inductively coupled, wherein the current is fed in such a way that the ohmic losses are as small as possible or minimal. This improves the efficiency of the system and allows the use of cables with a smaller cross-section as the primary conductor. In particular, when feeding in the current, the pulse width, pulse width ratio and / or the amplitude curve are specified, controlled or regulated. Information such as the number of consumers in a section of track,The amount of energy in the consumer's energy buffer and / or the consumer's respective power requirement can be taken into account. In an advantageous embodiment, the power requirement and / or the temporal progression of the power requirement of a consumer is determined in advance, in particular before it occurs. Advantageously, a critical value can thus be exceeded, since the current profile can be determined and thus also the precise thermal load on the primary conductor and other components. The maximum permissible temperature can thus always be taken into account. In an advantageous embodiment, a temporal progression of the current in the primary conductor is provided such that a critical value of the current is exceeded for a period of time, wherein the critical value is the maximum permissible current value for the primary conductor with a constant, permanent current value in the primary conductor and the period of time is so short thatthat no destruction of the primary conductor is to be expected from the current flow during this period. The critical current value is advantageously reached when a constant current value, in particular an effective alternating current value, is continuously applied. The resulting temperature is crucial here. At the critical value, a critical temperature is reached which, if exceeded, would lead to the destruction of the primary conductor. Further advantages arise from the subclaims. The invention will now be explained in more detail with reference to illustrations: Figure 1 schematically outlines a method for determining a value for the unrest of the primary conductor current. A system according to the invention for contactless energy transmission has a feed,which injects a medium-frequency alternating current into an elongated primary conductor of the system. Mobile consumers of the system are movable along the primary conductor and have a secondary coil inductively coupled to the primary conductor, by means of which energy can be extracted. In industrial applications, high currents occur, for which the primary conductor must be designed with a correspondingly large cross-section, which, however, leads to high costs. In addition, high ohmic losses occur. To detect an abnormal operating state of the system, in particular in which arcing fed by the primary conductor current is detectable due to defective compensation components or as a result of a severance of the primary conductor, in particular a line conductor, a value for the unrest of this current is calculated from the recorded values ​​of the primary conductor current. This value is determined as the difference between a continuously determined,in particular low-pass filtered, maximum value and a continuously determined, in particular low-pass filtered, minimum value, and this determined value is monitored for exceeding a permissible degree of deviation from a predetermined threshold. Thus, if the value for the disturbance of the primary conductor current exceeds a critical value, i.e., the threshold, a warning message is displayed and / or forwarded, or the feed-in is shut down. Pulse operation is thus unnecessary, and the associated power losses can also be avoided according to the invention. The value for the disturbance of the primary conductor current Î_Last is determined as the difference between the respectively updated maximum value Î_LastMaxFilter and the minimum value Î_LastMinFilter of the primary conductor current at the respective time step n according to the calculation rule in Figure 2: Here, n counts the time steps, and K_T determines the time constant of the low-pass filtering. The value for unrest is therefore low-pass filtered and expresses the volatility. For each time step, the newly updated maximum value Î_LastMaxFilter receives the value of the peak value, in particular the crest value, of the primary conductor current if this peak value is greater than or equal to the value Î_LastMaxFilterPT1; otherwise, the newly updated maximum value Î_LastMaxFilter receives the value Î_LastMaxFilterPT1, which is determined in each time step by being the sum of the value Î_LastMaxFilterPT1 that is one time step older and the difference between the peak value, in particular the crest value, and the value Î_LastMaxFilterPT1 that is one time step older, multiplied by the factor K_T.For each time step, the newly updated minimum value Î_LastMinFilter is given the value of the peak value, in particular the crest value, of the primary conductor current if this peak value is less than or equal to the value Î_LastMinFilterPT1; otherwise, the newly updated minimum value Î_LastMinFilter is given the value Î_LastMinFilterPT1, which is determined in each time step by being the sum of the value Î_LastMinFilterPT1 one time step older and the difference between the peak value, in particular the crest value, and the value Î_LastMinFilterPT1 one time step older, multiplied by the factor K_T. In particular, the factor K_T is chosen to be much smaller than 1, in particular smaller than one tenth.Instead of the value for unrest determined in this way, a sliding fluctuation range can also be used, which is also monitored for exceeding a permissible degree of deviation from a specified threshold. In each case, the threshold is either specified as a constant value or, alternatively, variable depending on the operating state. In the latter case, for example, a higher value is specified as the threshold when the system is started (i.e., the feed-in is switched on), compared to later, continuous operation, where a correspondingly lower value is specified as the threshold. When the feed-in is switched on, the rectifier is connected to the public AC voltage supply network, thus establishing the DC voltage supply for the output stage. In this way, large load current changes can be achieved without an arc occurring due to a cable break.Therefore, the temporal variation of the threshold value enables adaptation to the respective operating state of the system and thus reduces the probability of triggering false alarms. In a further development of the invention, if the permissible degree of deviation is exceeded, pulsed operation can also be carried out instead of shutdown, thus enabling continued operation of the system with increased safety. Thus, if the arc was only triggered accidentally, for example, by temporary maintenance or construction work, the system initially operates in pulsed mode to prevent permanent arcing. After a specified period of time, it can then return to normal operation, i.e., continuous operation.The overall advantage of controlling or regulating the pulse width of an inverter's output stage is that smaller currents occur over the system's service life or operating time, and thus lower ohmic losses occur. The output stage has at least two series circuits connected in parallel, with this parallel circuit being supplied from a DC voltage source. The DC voltage source is preferably a mains-supplied rectifier which provides the DC voltage on the output side. Each of the series circuits has two semiconductor switches, in particular MOSFETs or IGBTs, connected in series, which are controlled in a pulse-width modulated manner, with the pulse width modulation duration being the period T and the pulse width modulation frequency preferably being in the range between 10 kHz and 1 MHz. The primary conductor is supplied from the center taps of the series circuits.By repeatedly switching the output stage on and off over time, pulsed operation is possible, which extinguishes any arc that may have formed, because the pulse duration of pulsed operation is preferably in the range of 1 ms or more. Pulsed operation can also be operated with pulse-width modulation, whereby the pulse width ratio corresponds to the ratio of the on-time T_E to the off-time T_A. The period duration for pulsed operation is T_P. This is much longer than the period duration T of the medium-frequency current. The latter corresponds to a frequency of approximately 10 to 25 kHz. However, frequencies up to 50 kHz or even 1000 kHz are also usable.The loads comprise an energy buffer fed by the secondary coil, such as a smoothing capacitor connected downstream of the rectifier or a capacitor connected in parallel with the secondary coil, the capacitance of which is dimensioned such that an oscillating circuit is formed with the secondary coil whose resonant frequency is equal to the center frequency of the current in the primary conductor. Additional or different energy buffers can also be used. The energy capacity of the energy buffer(s) is utilized by the invention. This is because, during the time period T_A, the energy buffer supplies the load. During the time period T_E, the feed supplies the load and additionally replenishes the energy buffer. There are several design variants for pulsed operation: A first variant relates to the feed circuit comprising means for current and / or voltage detection, the measured values ​​of which are used to determine a power setpoint.If, for example, the power demand of the consumers increases, this can be detected by the change in the current and / or voltage measurements, and countermeasures can be carried out by increasing the pulse width ratio or the peak value of the primary conductor current. The means for current detection can be attached directly to the primary conductor. A means for voltage detection can be attached to a gyrator included in the feed circuit. The gyrator is shown in Figure 1 of DE 10053373, the features of the system for contactless energy transmission disclosed in the description of which are also encompassed by the present invention. In a second variant, the primary conductor has at least one or more track sections throughout the entire system, each of which is assigned a track controller comprising an electronic circuit and capable of exchanging data with the feed circuit.This makes it possible to transmit the number of consumers that need to be supplied in each section of track, as well as other data such as their required power and the available energy capacity in the energy buffer, to the feed-in circuit. This then allows the feed-in circuit to determine the required power and thus also the pulse width modulation ratio and / or the peak current curve in the primary conductor, and to apply it accordingly. In a third variant, the system even features consumers that are connected to the feed-in circuit for data exchange, either directly or via a respective line controller.This allows the loads to transmit the power they currently require and / or the amount of energy available in their energy buffer, and adjusts the primary conductor current feed circuit accordingly, with the pulse width modulation ratio and / or the primary conductor current peak value curve then depending on this transmitted information. State-of-the-art bus systems can be used for data transmission in stationary applications. For transmitting data to or from movable loads, transmission via radio waves, infrared waves, other electromagnetic waves, or ultrasonic waves is advantageous. A slotted coaxial cable laid along the primary conductor can also be used if the mobile component moves a suitable antenna along the slots of the coaxial cable.Modulating the information onto the primary conductor current at frequencies higher than the medium frequency is also advantageous for data transmission. In a fourth variant, the secondary coil is connected to a current-to-voltage converter, the output of which supplies a rectifier. The DC voltage thus generated can be used as an intermediate circuit voltage for a converter powering an electric motor. The current-to-voltage converter is constructed from passive electronic components such as inductors, capacitors, and resistors. Since the primary-side supply circuit injects a medium-frequency current, thus essentially exhibiting current source behavior, the DC voltage provided by the rectifier on the secondary side is constant. This is because the rectifier output is connected to a capacitor acting as an energy storage device, which buffers the DC voltage.If the current peak value Î in the primary conductor were to be reduced, the DC voltage, i.e. the intermediate circuit voltage, would be reduced accordingly, for example by the same factor as the current peak value Î in the primary conductor. However, since the current in the primary conductor is provided with the full current peak value Î in the present invention, the rectified voltage is also always at its correspondingly high value. The energy buffer is designed in such a way that it buffers the voltage over the off-time T_A, i.e. allows it to drop only insignificantly. In a further embodiment of the invention, the current-voltage converter is designed for higher power. It can therefore also be used in a system where the current in the primary conductor is permanently at its peak value. However, the same current-voltage converter can also be used in a system with a pulse width modulation ratio of less than 100%.In this way, the variety of current-voltage converter variants can be restricted. This also allows the costs of the entire system series to be reduced. A drive for a mobile consumer, i.e. a vehicle, for example, comprises a converter to supply the electric motor, which in turn drives the vehicle, or an axle of a machine. Via information transfer, the drive, in particular the converter, is informed that it should start the vehicle from time t_0. This also informs it that the vehicle should reach a specifiable target speed. This enables the converter to specify the maximum torque, and therefore the maximum possible acceleration, from time t_0. After an initial period of time, which can be determined by the converter or a computer, the target speed is reached and only a low torque needs to be applied to overcome rolling and / or sliding friction.As described above, the drive is supplied contactlessly from the primary conductor. Only a critical maximum continuous current value is permitted in the primary conductor. If this value is continuously exceeded, the risk of component damage increases, for example, due to melting of the insulation or the copper wires of the primary conductor. Starting the vehicle as described above requires an idealized temporal profile of the electrical power P, which must be supplied from the primary conductor to the drive, as shown in Figure 2. During pulsed operation, the converter is able to briefly exceed the critical current value due to a sharp increase in power demand.To do this, the converter predicts the power demand and thus also the current flow in the primary conductor and determines the permissible period for the short-term exceedance of the critical current value. The predicted, i.e. previously determined, power demand is reported to the feed-in, which then takes it into account accordingly, i.e., a correspondingly excessive current is fed into the primary conductor. In a further embodiment according to the invention, only one consumer is provided. Thus, the previously determined consumption can be assigned precisely to this consumer, and the current excess is determined for this consumer. In a further embodiment according to the invention, multiple consumers are provided. Each consumer reports its predicted power demand to the feed-in, which then feeds in the total required power.

[0002] List of reference symbols 1 Analog-digital converter 2 Maximum value filter 3 Minimum value filter Î_Last Load current, especially primary conductor current Î_LastMaxFilter Maximum value Î_LastMinFilter Minimum value Î_Last_Unruhe Measure for fluctuation or volatility of the load current Î_Last

Claims

Patent claims:

1. System for contactless energy transmission, comprising a feed which impresses a medium-frequency alternating current into a primary conductor to which at least one secondary coil for supplying at least one consumer is inductively coupled, wherein the feed has a current sensor for detecting the alternating current, characterized in that the feed has a means for determining a value of the unrest, in particular volatility, of the peak value, in particular crest value, of the alternating current, wherein the means is connected to a monitoring means which monitors the value for exceeding a permissible degree of deviation from a threshold value, in particular wherein the monitoring means is designed to display or forward warning information depending on the result of the monitoring and / or to switch off the feed or at least temporarily convert it into pulsed operation.

2. System according to claim 1, characterized in that the threshold value is constant or that the threshold value has different values ​​depending on the operating state of the system, in particular wherein the predetermined threshold value is greater at a first point in time than at a second point in time, in particular thus at a later point in time, in particular wherein during a period when the feed-in is switched on, in particular thus at the beginning of the electrical supply of the feed-in by the public AC voltage supply network, the predetermined threshold value is greater than during later operation, in particular continuous operation, of the feed-in. 3.System according to at least one of the preceding claims, characterized in that the value of the unrest is a temporally slidingly determined fluctuation range of the peak values, in particular peak values, of the alternating current or that the value of the unrest is determined as the difference between - a, in particular temporally slidingly determined, PT1 and / or low-pass filtered maximum value of the peak values ​​and - a, in particular temporally slidingly determined, PT1 and / or low-pass filtered minimum value of the peak values.

4. System according to at least one of the preceding claims, characterized in that the current sensor has an analog-to-digital converter for providing the detected current values ​​as a digital data stream.

5. System according to at least one of the preceding claims, characterized in that for each time step, the value of the disturbance is determined as the difference between a maximum value and a minimum value, wherein in each time step, the newly updated maximum value Î_LastMaxFilter is assigned the value of the peak value, in particular the crest value, of the alternating current if this peak value is greater than or equal to the value Î_LastMaxFilterPT1, and otherwise the newly updated maximum value Î_LastMaxFilter is assigned the value Î_LastMaxFilterPT1, which is determined in each time step bythat it is determined as the sum of the one time step older value Î_LastMaxFilterPT1 and the difference between the peak value, in particular the crest value, and the one time step older value Î_LastMaxFilterPT1, multiplied by the factor K_T, in particular wherein the factor K_T is chosen to be much smaller than 1, in particular smaller than one tenth.

6. System according to at least one of the preceding claims, characterized in that in each time step, the newly updated minimum value Î_LastMinFilter is assigned the value of the peak value, in particular the crest value, of the alternating current if this peak value is smaller than or equal to the value Î_LastMinFilterPT1, and otherwise the newly updated minimum value Î_LastMinFilter is assigned the value Î_LastMinFilterPT1, which is determined in each time step bythat it is determined as the sum of the value Î_LastMinFilterPT1 which is one time step older and the difference between the peak value, in particular the crest value, and the value Î_LastMinFilterPT1 which is one time step older, multiplied by the factor K_T.

7. System according to at least one of the preceding claims, characterized in that the feed is suitably designed for pulsed operation, in which a pulse width, pulse width ratio, and / or the amplitude characteristic of the alternating current can be specified, controlled, or regulated, in particular after the permissible degree of deviation from the threshold value is exceeded.

8. System according to at least one of the preceding claims, characterized in that the primary conductor is provided in an elongated manner, in particular laid on the ground, in particular wherein the load is arranged to be movable along the primary conductor. 9.System according to at least one of the preceding claims, characterized in that the center frequency is between 10 and 1000 kHz, and / or that the pulse width, pulse width duration and / or the characteristic time in the amplitude modulation, such as amplitude modulation period duration, is greater than the period duration of the medium-frequency current, in particular ten times greater or more, and / or that the pulse width ratio is matched to the energy buffer and power consumption of the consumer.

10. System according to at least one of the preceding claims, characterized in that the secondary coil is attached to the load, wherein the load is arranged to be movable along the primary conductor with the secondary coil, in particular wherein the primary conductor is provided such that the load is arranged to be rotatable relative to the primary conductor.

11. System according to at least one of the preceding claims, characterized in that a line controller is assigned to each of the primary conductor or sections of the primary conductor, and / or that means for exchanging data from the feeder, the line controller, and / or the load(s) are included. 12.System according to at least one of the preceding claims, characterized in that the pulse width, the pulse width ratio and / or the amplitude curve of the feed-in can be specified as a function of data such as the number of consumers in a section of the route, the amount of energy in the energy buffer of the consumer, and the respective power requirement of the consumer.

13. System according to at least one of the preceding claims, characterized in that a consumer comprises means for determining the temporal course of its power demand or current demand, and / or that a consumer comprises means for transmitting information about the temporal course of its power demand or current demand to the feed-in or to a computer connected to the feed-in for signal or information transmission.

14. Method for operating a system for contactless energy transmission, wherein medium-frequency alternating current is impressed from a feed into an elongated primary conductor to which at least one secondary coil for supplying at least one consumer is inductively coupled, wherein the alternating current is detected, characterized in that a value of the unrest, in particular volatility, of the peak value, in particular crest value, of the alternating current is determined and this value is monitored for exceeding a permissible degree of deviation from a threshold value, in particular wherein, depending on the result of the monitoring, warning information is displayed and / or forwarded or the feed is switched off or at least temporarily converted into pulsed operation.

15. Method according to the preceding claim, characterized in that the current is fed in such a way that the ohmic losses are as small as possible or minimal, and / or that when feeding in the current, the pulse width, pulse width ratio and / or the amplitude curve is specified, controlled or regulated, and / or that information such as the number of consumers in a section of the route, the amount of energy in the consumer's energy buffer and / or the respective power requirement of the consumer is taken into account, and / or that the power requirement and / or the temporal progression of the power requirement of a consumer is predetermined, in particular before it occurs, and / or that such a temporal progression of the current in the primary conductor is provided that a critical value of the current is exceeded for a period of time,where the critical value is the maximum permissible current value for the primary conductor at a constant permanent current value in the primary conductor and the time period is so short that the current flow during this time period is not expected to cause destruction of the primary conductor.

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