Systems and methods for supplying an electrical charge for stunning an animal

Abstract

System for supplying electrical charge for stunning an animal, e.g. poultry, the system comprising: power inlet for receiving an input power; frequency converter for converting the input power into a transformed power; control unit configured to control the frequency converter, wherein the control unit is configured to control a switching frequency of the converter to generate the transformed power at a controllable frequency; sine filter configured to filter out harmonics of the voltage of the transformed power to provide a filtered power for providing the electrical charge, wherein the filtered power has voltage with a sine-shaped waveform.

Description

[0001] SYSTEMS AND METHODS FOR SUPPLYING AN ELECTRICAL CHARGE FOR STUNNING AN ANIMAL

[0002] The present invention relates to the field of stunning animals, e.g. poultry. The present invention relates in particular to systems and methods forsupplying an electrical charge for stunning an animal.

[0003] Stunning is a widely used method to render animals unconscious before slaughter. This involves delivering an electrical charge to the animal. The effectiveness of electrical stunning is determined by factors such as voltage, current, waveform, and duration.

[0004] Historically, most electrical stunning systems have relied on analog circuitry to regulate and deliver the electrical charge. While analog systems have been widely implemented due to their simplicity and cost-effectiveness, they exhibit significant limitations in precision, adaptability, and reliability. Analog systems are inherently less flexible in adjusting parameters. This lack of adaptability can result in either insufficient stunning, causing unnecessary animal suffering, or excessive energy delivery, leading to tissue damage and reduced meat quality. Additionally, analog systems are susceptible to drift in component performance over time due to factors such as wear and temperature fluctuations. This can further compromise the consistency and reliability of the stunning process.

[0005] Some modern systems utilize digital systems to regulate the delivery of a direct current (DC) charge. Digital systems offer improved parameter control and adaptability compared to their analog counterparts. However, DC stunning can reduce the effectiveness of the stunning process. Moreover, the high-energy DC pulses often required for effective stunning can cause localized tissue damage, negatively impacting the quality and appearance of the meat.

[0006] It is an object of the invention to overcome the disadvantages of the prior art, or at least provide an alternative to the prior art. It is in particular an object of the invention to provide a charge with alternating current having a sine-shape, which is digitally controllable.

[0007] One or more objects are achieved with system forsupplying an electrical charge for stunning an animal, e.g. being poultry, the system comprising:• a power inlet configured to receive an input power;

[0008] • a frequency converter configured to convert the input power into a transformed power;

[0009] • a control unit configured to control the frequency converter, wherein the control unit is configured to control a switching frequency of the converter to generate the transformed power in a controllable frequency;

[0010] • a sine filter configured to filter out harmonics of the voltage of the transformed power to provide a filtered power for providing the electrical charge, wherein the filtered power has voltage with a sineshaped waveform.

[0011] The invention thus relates, in embodiments, to a system for supplying an electrical charge for stunning an animal. The stunning can e.g. be meant to render the animal unconscious, although in some cases it can also be used to kill the animal. The animal can e.g. be poultry, e.g. chicken, broilers, duck, turkey, geese, pheasant, pigeon. The animal can e.g. be a cattle (e.g. a cow), a pig, a sheep, a goat, a rabbit, fish. The system can e.g. be configured to supply the electrical charge to a bath, e.g. containing a fluid (e.g. water, optionally with some additional components), wherein the animal (e.g. at least the head) is moved through the bath. The system can e.g. be configured to supply the electrical charge to electrodes, e.g. configured to be in contact with the animal, e.g. placed on both sides of the head.

[0012] The system comprises a power inlet configured to receive an input power. The input power can be based on an input voltage (e.g. an alternating voltage). That is, the system is voltage driven and controlled. However, it is envisaged that the invention can also be applied when the input power is based on an input current. The input power can e.g. be a power (e.g. voltage or current) with an alternating voltage / current. The input voltage of the input power can e.g. be at a voltage between 50-600V (e.g. between 380-500V), e.g. at 400V, at 230 V, at 120 V. The input current of the input power can be at a current between 0.5-25A, e.g. between 15-25 A, e.g. at 20A. The input power can have a frequency e.g. at 50Hz or at 60Hz. The input power can e.g. be a one-phase power, a two-phase power, or a three phase power. The input power can e.g. be two-phase power at 400V and 20A.The system comprises a frequency converter. The frequency converter converts the input power into a transformed power. For example, the frequency converter converts the input voltage into a transformed voltage. The transformed power is at a different frequency than the input power. Optionally, the transformed power is at a different voltage than the input power.

[0013] The frequency converter can e.g. be configured to first convert the input power (e.g. having an alternating voltage / current) into a power with a direct current (DC) (e.g. into a DC voltage), e.g. through a rectification process. The frequency converter can e.g. comprise a rectifier stage for this. The rectifier stage can e.g. comprise at least a diode or a thyristor bridge, and optionally a capacitor. The rectifier stage can e.g. comprise an active front end, e.g. comprising one or more active switches (e.g., IGBTs or MOSFETs).

[0014] The frequency converter can e.g. be configured to convert said power (with direct current (voltage) into a power with an alternating voltage / current, e.g. at a desired frequency. The frequency converter may e.g. comprise an inverter stage for this. The inverter stage may comprise one or more switches. The switches can e.g. be insulated-gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs).

[0015] The frequency converter can e.g. be a static frequency converter, a rotary frequency converter, a hybrid frequency converter, a direct frequency converter, a cycloconverter.

[0016] Optionally, the frequency converter comprises a DC link stage, e.g. configured to filter and / or store the direct current voltage. The DC link may e.g. comprise capacitors and / or inductors. The DC link may e.g. be able to provide a stable power supply to the inverter stage.

[0017] The system further comprises a control unit, which may e.g. be or comprise a microcontroller, which may e.g. comprise a digital signal processor. The control unit is configured to control the frequency converter for controlling the transformed power. In particular, the control unit is configured to control the frequency of the voltage (or current) of the transformed power as a controllable frequency. The control unit can e.g. be configured to control a switching frequency of one or more switches (of the frequency converter). This can be used to control the controllable frequency. Theswitching frequency relates to the frequency at which the one or more switches can be switched, which can e.g. be at 150 kHz. The switches can e.g. be IGBTs or MOSFETs, and can e.g. be arranged in the inverter stage. The control unit can e.g. be configured to generate Pulse Width Modulation (PWM) signals or Pulse Density Modulation (PDM) signals to control the switches. When the rectifier stage of the frequency converter comprises active switches (e.g. when comprising an active front end), the control unit can also be configured to control the switches of the rectifier stage.

[0018] The control unit can be any type of suitable type of control unit, e.g. being embodied in a computer, PLC, raspberry pi, or the like. The control unit can e.g. comprise one or more input terminals, output terminals, or communication terminals for communicating with other components. Said communication can be wired or wireless, according to any of suitable communication method or protocol, e.g. using Bluetooth or a Wi-Fi network.

[0019] Optionally, the system comprises one or more sensors configured to generate a sensor signal and provide this to the control unit, wherein the control unit is configured to control the switches based on said sensors signal. The sensors may e.g. be configured to determine or more of the current, and / or voltage, and / or frequency of the input power; and / or current, and / or voltage, and / or frequency of the transformed power.

[0020] Since the transformed power is generated by (digitally) controlling switches, the waveform of the transformed power may be stepped or modulated rather than a perfect or pure sine wave. The waveform may comprise harmonic distortion.

[0021] The system further comprises a sine filter, which preferably is a passive sine filter. The sine filter can e.g. be a low-pass filter or a band-pass filter. The (passive) sine filter provides a filtered power. The filtered power corresponds to the transformed power, having harmonics of the voltage and / or current filtered out. The (passive) sine filter is configured to smooth out the output (the transformed power, in particular the voltage thereof) of the frequency converter. The filtered power as such has a voltage (and current) with a waveform that is significantly less stepped or modulated than the transformed power. The sine filter may e.g. be a low-pass filter.

[0022] The (passive) sine filter may e.g. be configured to filter out harmonics of the voltage of the transformed power when said voltage is at a frequency within a predetermined range (the sine filter can be a band-pass filter in these embodiments).Said predetermined range may e.g. be between 200-1800 Hz, e.g. between 400-1500 Hz, e.g. between 1000-1500 Hz.

[0023] The passive sine filter is configured to remove the high-frequency components from the transformed power (which may be a PWM signal) using one or more passive components. The passive components may e.g. comprise one or more inductors, e.g. configured (and positioned) to block high-frequency components by providing impedance to rapid changes in voltage (or current). The passive components may e.g. comprise capacitors, e.g. configured (and positioned) to smooth out voltage fluctuations by absorbing high-frequency components. The passive components may e.g. comprise resistors, e.g. configured to prevent oscillations.

[0024] The sine filter is configured to provide the filtered power having a sine-shaped waveform. The control unit may be configured to control the frequency converter to generate the transformed power as having a waveform of a stepped approximation of a sine shape, and the sine filter then filters out the high frequency components to generate a pure sine-shaped waveform. In this context, a pure sine-shaped waveform can e.g. correspond to having a (total) harmonic distortion of 3 or less, e.g.2 or less, e.g.

[0025] 1.50 or less, e.g. 1.40 or less. Preferably, the harmonic distortion is 1.41 + / - 0.02% or less. For example, Total harmonic distortion (THD) of the output voltage is defined as THD = where I^is the RMS value of the fundamental at / oand ykare RMS values

[0026]

[0027] of the Zc-th harmonics, determined from a spectrum analysis within a specified bandwidth; THD is expressed as a percentage.

[0028] In embodiments, the control unit and the frequency converter are configured to allow the switching frequency to reach 70 kHz or more, preferably 100 kHz or more, preferably 150 kHz or more. For example, the control unit and frequency converter are configured to modulate the power with a switching frequency of 150 kHz. The frequency converter can (e.g. in the inverter stage) comprise one or more switches designed to allow said switching frequencies. Said switches can e.g. include MOSFETs. Said switches can e.g. include wide-bandgap semiconductors (e.g. SiC and / or GaN transistors). SiC (Silicon Carbide) and GaN (Gallium Nitride) transistors can be advantageous to allow high switching frequencies with low losses. Diamond, Ga2O3, or AIN based semiconductor components may also be used to enable high switching frequencies.It may in particular be advantageous when switching frequencies as mentioned above can be reached when the input power is relatively high and / or has a current that is relatively high. For example, the input power may have a current at 10A or more, e.g. at 15A or more, e.g. around 20A. For example, the input power may be at 4 kW or higher, e.g. 8 kW or higher. For example, the input power may be at 400V and 20A, and the switching frequency may be at 150kHz.

[0029] In embodiments, the passive sine filter is a second order filter. The passive sine filter may e.g. comprise two cascaded first order filters, wherein each first order filter may e.g. be an RC filter or an RL filter. The passive sine filter may e.g. comprise two reactive components, e.g. inductors and / or capacitors. The passive sine filter may e.g. be configured to attenuates high-frequency components (such as harmonics or switching noise) at a rate of 12 dB per octave or 40 dB per decade. It has been found that a second order filter achieves a good balance of filtering out high harmonics while limiting power losses, for the application of stunning animals.

[0030] The second order filter may e.g. be an LC filter, having an inductor in series and capacitor in parallel to the load. The inductor smoothens the signal, while the capacitor filters ripples.

[0031] The second order filter may e.g. be a Pi filter, having two capacitors with an inductor in between: one capacitor at the input, one at the output, and an inductor in series. This may provide better harmonic suppression compared to a single LC filter.

[0032] The second order filter may e.g. be a T filter, having two inductors with a capacitor in between: One inductor at the input, one at the output, and a capacitor in parallel. This may provide robust attenuation for high-frequency noise.

[0033] In embodiments, the passive sine filter is an n order filter, wherein n is two or more, optionally three or more. The passive sine filter may e.g. comprise two or more cascaded first order filters, wherein each first order filter may e.g. be an RC filter or an RL filter.

[0034] In embodiments, the system further comprises an active front end. The active front end (AFE) may e.g. be comprised by the frequency converter. For example, the active front end may be configured to convert the input power (which has an AC voltage) into a power with a DC voltage. The frequency converter may further comprisean inverter stage forgenerating the transformed power, wherein the transformed power has an AC voltage. Optionally, the frequency converter also comprises a DC link.

[0035] The active front end may e.g. comprise one or more active switches (e.g., IGBTs or MOSFETs). The control unit may be configured to control said switches. Optionally, the control unit comprises a first microcontroller configured to control the switches of the inverter stage, and a second microcontroller to control the switches of the active (bidirectional) front end.

[0036] The active (bidirectional) front end allows bidirectional power flow. It has been found that, in practice, the stunner may cause a reversed charge to return into the system when said system is supplying the electrical charge. Conventional systems (e.g. rectifiers using only diodes or thyristors) are not designed to receive such reversed charge, which may therefore cause failure of components. The inventors have found that this can be resolved by providing an active front end.

[0037] The control unit may e.g. be configured to apply pulse width modulation (PWM) to control the switches of the active front end. The control unit may e.g. be configured to apply Pulse Density Modulation (PDM) to control the switches of the active front end.

[0038] Optionally, the system comprises one or more sensors configured to generate a sensor signal and provide this to the control unit, wherein the control unit is configured to control the switches of the active front end based on said sensors signal. The sensors may e.g. be configured to determine or more of the current, and / or voltage, and / or frequency of the input power; and / or current, and / or voltage, and / or frequency of the current outputted by the active front end.

[0039] In embodiments, the system further comprises a filter for the active front end. The filter for the active front end may herein also be referred to as the AFE filter. The AFE filter may optionally be integrated into the active front end. The AFE filter may be advantageous to mitigate high-frequency noise, harmonics, and / or disturbances generated by the switching devices (e.g., IGBTs or MOSFETs) in the AFE.

[0040] The AFE filter may e.g. be a passive filter. The AFE filter may e.g. be an (active) harmonic filter. The AFE filter may e.g. be a hybrid filter, combing active and passive components. The AFE filter may e.g. comprise one or more inductors, e.g. arranged as input line reactors. The inductor may e.g. be installed at the input of the active frontend. The inductor may e.g. be configured to reduce harmonics and limit current spikes caused by the switching operation. The AFE filter may e.g. comprise one or more capacitors, e.g. configured to filter out high-frequency noise, e.g. by providing a path for high-frequency currents to ground. The AFE filter may e.g. comprise one or more resistors, e.g. arranged as damping resistors, e.g. configured to prevent resonance between the inductors and the capacitors. The AFE filter may e.g. comprise one or more EMI filters, e.g. arranged to reduce electromagnetic interference. The AFE filter may e.g. comprise one or more high frequency chokes, e.g. comprising one or more inductors, e.g. configured to reduce high-frequency noise.

[0041] In embodiments, the system is configured to provide an output voltage (e.g. the voltage of the filtered power) having a waveform in a sine-shape, e.g. having a total harmonic distortion of 3 or less, e.g.2 or less, e.g. 1.50 or less, e.g. 1.40 or less. For example, the total harmonic distortion may be 1.41 + / -0.02% or less. The output voltage may e.g. have a pure sine-shaped waveform. It has been found that a pure sine-shaped waveform may be advantageous for the effectiveness in stunning the animal and animal welfare. Advantageously, the invention allows for a controllable frequency of the sine-shaped waveform, while providing low harmonic distortion.

[0042] In embodiments, the control unit is configured to control the switching frequency such that the controllable frequency is adjustable (e.g. stepless adjustable), e.g. between at least 1000-1500 Hz or between 400-1500 Hz. Thus, the control unit can control the switches of the frequency converter (e.g. in the inverter stage and optionally in the rectifier stage) such that the controllable frequency of the sine-shaped waveform of the filtered power can be at any selected frequency within said range, e.g. within a resolution of 10 Hz or smaller, e.g. 5 Hz or smaller, e.g. 1 Hz or smaller. This may e.g. in particular be achievable when the control unit and the frequency converter are configured to allow the switching frequency to reach 70 kHz or more, preferably 100 kHz or more, e.g. up to 150 kHz or more.

[0043] In embodiments, the input power has a voltage of approximately 400 V and a current of approximately 20 A.

[0044] In embodiments, the frequency converter is a two-phase frequency converter. For example, the input current may be a two-phase current, e.g. from a two-phase electrical system.In embodiments, the frequency converter is a SiC-based frequency converter. The frequency converter may comprise one or more SiC (Silicon Carbide) semiconductor devices (e.g. transistors, switches, MOSFETs, diodes). For example, the switches in the frequency converter (e.g. in the inverter stage and optionally in the rectifier stage, e.g. when comprising an active front end) can comprise SiC. For example, the wafer or base material can comprise or be made from SiC. Optionally, for applicable embodiments, the active regions (e.g. drift region, junction, and / or gate structure) comprise or are made from SiC. These can be doped with impurities (e.g., nitrogen, aluminum) to create n-type and p-type regions for the functioning as a switch. SiC material can form the main conductive channel and the region where current flows during operation.

[0045] Compared to traditional silicon-based components, SiC is a wide-bandgap material which allows for high efficiency, high power, and high performance, in particular at high switching frequencies. This in turn also allows the passive components (e.g. in the sine filter) to be dimensioned smaller.

[0046] For example, the frequency converter may comprise, e.g. in the rectifier stage, one or more SiC Schottky Barrier Diodes or MOSFETs, e.g. to rectify the input AC to DC. This may e.g. result in lower forward voltage drops, reducing conduction losses.

[0047] For example, the frequency converter may comprise, e.g. in the inverter stage, one or more SiC MOSFETs, e.g. for converting the DC to the transformed power (being AC). Using SiC switches allows high switching frequencies (even at high powers) with relatively small harmonic distortion.

[0048] In embodiments, the frequency converter is a Gallium Nitride (GaN) based frequency converter, comprising one or more GaN-based semiconductors. In embodiments, the frequency converter comprises one or more diamond-based semiconductors. In embodiments, the frequency converter comprises one or more Gallium Oxide (Ga2O3)- based semiconductors. In embodiments, the frequency converter comprises one or more Aluminum Nitride (AIN)- based semiconductors. In these embodiments, the respective semiconductor can be any of the components mentioned above for SiC. Moreover, different semiconductors based on different materials (including SiC, GaN, diamond, Ga2O3, AIN) can be combined in a single frequency converter.In embodiments, the control unit is configured to receive on input signal, and control the frequency converter based on the input signal. The control unit can e.g. be configured to control the controllable frequency based on the input signal. The control unit can e.g. be configured to control the voltage of the transformed power based on the input signal. The input signal can e.g. relate to a desired frequency of the electrical charge provided to a stunner, and / or the control unit can be configured to determine a desired frequency based on the input signal.

[0049] In embodiments, the system further comprises a sensor system for detecting one or more characteristics of the animals to be stunned, wherein the sensor system is configured to generate to input signal. The characteristics can e.g. relate to one or more of: the type of animal (e.g. species, and / or race / subspecies of a species), the quantity of animals to be stunned at a given moment, the size of the animal, the weight of the animal.

[0050] In embodiments, the system further comprises an operator input system configured to receive commands from an operator, wherein the operator input system is configured to generate the input signal based on a command of the operator.

[0051] In embodiments, the system may comprise an isolation transformer, wherein the isolation transformer may e.g. be configured to receive the filtered power and to provide the electrical charge (e.g. having the outlet voltage) to a stunner. The isolation transformer may be advantageous to electrically isolate the upstream components from the stunner, and prevent a DC (voltage) from passing.

[0052] In embodiments, the invention relates to a stunning system, comprising a system for supplying an electrical charge according to any of the embodiments described herein, and a stunner configured to receive the electrical charge from said system and subject an animal to a potential difference based on said electrical charge.

[0053] For example, stunning system may comprise a fluid bath, configured to receive a part of the animals, e.g. including the head of the animals. The stunner may be configured to apply the electrical charge to the fluid in the bath. The system may comprise an overhead conveyor system for conveying the animals, e.g. in shackles. The shackles can e.g. be grounded, such that the animals are exposed to the potential difference between the fluid bath and the grounded shackles. A plurality of animalsmay be moved through the fluid bath at the same time, e.g. at least 10 animals, e.g. at least 12, or at least 16. The animal may e.g. be poultry.

[0054] However, other embodiments are also possible. For example, the stunner comprise electrodes that are configured to be brought in contact with the animal, e.g. being arranged on the head of the animal.

[0055] The invention further relates to a method for supplying an electrical charge for stunning an animal. Although the method can be performed using the system according to the invention; neither the system, nor the method is limited thereto. Features explained herein with reference to the system have the same meaning with respect to the method unless explicitly defined otherwise. Features explained with reference to the system can be applied mutatis mutandis to the method to achieve the similar advantages, and vice versa.

[0056] One or more objects of the invention can be achieved with a method for supplying an electrical charge for stunning an animal, comprising a step of using a system according to the any of the embodiments described herein, e.g. for supplying the electrical charge, and e.g. further including a step of subjecting one or more animals to said electrical charge.

[0057] One or more objects of the invention can be achieved with a method for supplying an electrical charge for stunning an animal, e.g. being poultry, the method comprising:

[0058] • receiving an input power;

[0059] • converting the input power into a transformed power using a frequency converter;

[0060] • controlling a switching frequency of the converter to generate the transformed power at a controllable frequency;

[0061] • using a sine filter to filter out harmonics of the voltage of the transformed power to provide a filtered power having a voltage with a sine-shape waveform for providing the electrical charge

[0062] The method may further comprise a step of subjecting one or more animals to said electrical charge.It is noted that the active front end may be advantageous for any type of system supplying an electrical charge for stunning an animal. Therefore, the invention may, in embodiments, relate to:

[0063] A system for supplying an electrical charge for stunning an animal, e.g. being poultry, the system comprising: a power inlet configured to receive an input power; an active front end, optionally a filter for the active front end. The active front end and the components associated therewith may be embodied according to any of the embodiment described herein. This system may further comprise any of the components and / or features explained herein. The system comprising the active front end may in particular be used in combination with a stunner, wherein the stunner is configured to supply the electrical charge to a bath, e.g. containing a fluid (e.g. water, optionally with some additional components), wherein the animal (e.g. at least the head) is moved through the bath. The animal may e.g. be poultry.

[0064] Exemplary embodiments of the invention are described using the figures. It is to be understood that these figures merely serve as examples of how the invention can be implemented and are in no way intended to be construed as limiting for the scope of the invention and the claims. Like features are indicated by like reference numerals along the figures. In the figures:

[0065] Fig 1: schematically illustrates a system for stunning poultry;

[0066] Fig. 2: schematically illustrates the system for supplying the electrical charge

[0067] Fig. 1 schematically illustrates a stunning system 1 for stunning poultry. The system 1 comprising a stunner 3 and a system 2 for supplying an electrical charge 41 to the stunner 3. Although the invention is explained below with reference to stunning poultry in a fluid bath 33, it is noted that the invention can be applied to other stunning applications as well.

[0068] Poultry carcasses 10 are conveyed by an overhead conveyer 20. The conveyor 20 comprises shackles 22 for holding the poultry 10 by the legs 11 or feet. The shackles 22 are moved in a conveying direction 21 through the stunning system 1.

[0069] The stunning system 1 comprises a fluid bath 33 in which a fluid 31 is arranged. The fluid 31 may be water-based. While the overhead conveyor 20 moves the poultry10 through the stunning system 1 , the shackles 22 are descended such that the head 12 of the poultry 12 is moved through the fluid 31.

[0070] An electrode 32 is arranged at the bottom of the fluid bath 33. The electrical charge 41 is provided to the electrode 32, such that the fluid 31 is charged with the electrical charge. The shackles 22 are grounded via grounding elements 23, 24 and ground connection 42. The poultry 10 having its head 12 in the fluid 31 is as such subjected to a potential difference between the electrode 32 and the ground. This potential difference results in the stunning of the poultry. An isolated entry plate 35 may furthermore be provided to separate the poultry at the entry of the stunning system 1 from poultry already arranged in the fluid bath 33, therefore preventing pre-stun shocks.

[0071] The stunning system 1 will render the poultry unconscious. Downstream of the stunning system 1, the overhead conveyor 20 may transport the poultry 10 through a killing installation. The killing installation may be configured to slit one or more veins in the neck of the poultry 10. Stunning the poultry 10 prior to the killing is preferred to reduce the suffering of the animals.

[0072] It has been found that the electrical charge 41 to which the poultry is subjected during the stunning may affect the quality of the meat as well as the suffering of the animal. It may thus be advantageous to regulate and control this electrical charge. The stunning system 1 therefore comprises a system 2 for supplying the electrical charge, which may have several components arranged within a housing 51. An operator control panel 52 may allow an operator to control the frequency and voltage of the electrical charge 42.

[0073] Fig. 2 schematically illustrates the system 2 for supplying the electrical charge 41. The system 2 comprises a power inlet 91 for receiving an input power 61. The input power may e.g. be provided from the mains at the slaughterhouse where the stunning system is arranged. The input power 61 may be a two-phase power with alternating voltage at 400V, and alternating current at 20A, e.g. being at a frequency of 50 or 60 Hz (depending on geographical location). The system 2 converts this input power 61 into the electric charge 41. The system 2 is able to control the frequency and voltage of the electrical charge 41, while providing a pure sine-shaped waveform.

[0074] The system 2 comprises a frequency converter 70 for converting the input power 61 (which is at a fixed frequency) into a transformed power 64. The transformed power64 has a controllable frequency and voltage. The frequency converter 70 comprises a rectifier stage 71 , optionally a DC link 74, and an inverter stage 75. In addition, the system 2 may comprise a fuse (not shown) between the power inlet 91 and the frequency converter 70 for protection.

[0075] The rectifier stage 71 in the shown example comprises an active front end 72. The active front end 72 comprises actively controlled semiconductor switches, such as insulated-gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs). The rectifier stage 71 converts the alternating voltage of the input power 61 into power 62 with a DC voltage 62. Using an active front end 72 rather than a passive rectifier stage may in particular be advantageous for the application of stunning animals (e.g. in a fluid bath), since the inventors have found that a reversed charge (current) may occur in practice. This could damage components when a passive rectifier stage is used.

[0076] The rectifier stage 71 comprises an AFE filter 73. The AFE filter 73 is integrated with the active front end 72 in the rectifier stage 71. The AFE filter may be advantageous to mitigate high-frequency noise, harmonics, and / or disturbances generated by the switches in the active front end. The AFE filter 73 may e.g. comprise one or more inductors arranged as input line reactors, and / or one or more capacitors configured to filter out high-frequency noise. The AFE filter 73 may also comprise one or more resistors, e.g. arranged as damping resistors. The AFE filter 73 may also comprise one or more EMI filters and / or high frequency chokes.

[0077] The DC link 74 connects the rectifier stage 71 to the inverter stage 75 and serves as an energy buffer. The DC link 74 receives the power 62 with DC voltage and provides a DC voltage power 63 to the inverter stage 75. The DC link 74 may comprise capacitors to smooth the rectified DC voltage 62 by filtering high-frequency ripples and optionally inductors stabilize the voltage / current flow and improve power quality.

[0078] The inverter stage 75 converts the DC voltage power 63 back into power 64 with an AC voltage, said power being the transformed power 64 with a selectable / controllable frequency and voltage. Said inverter stage 75 comprises one or more semiconductor switches, e.g. IGBTs or MOSFETs.

[0079] The frequency converter 70 is configured to allow high frequency switching (e.g.

[0080] 150 kHz), while also allowing high power (e.g.20A 400V input power 61 ). To achieve this,the frequency converter 70 can comprise SiC (Silicon Carbide) semiconductor devices. The transistors, switches, MOSFETs, diodes of the rectifier stage 71 and the inverter stage 75 can be SiC-based. This enables the frequency converter 70 for switching frequencies of 100 kHz or more, preferably up to 150 kHz (or more).

[0081] The system 2 further comprises a control unit 80. The control unit 80 is a microcontroller 80 in the shown example, which controls both the rectifier stage 71 and the inverter stage 75. However, it may also be possible that the control unit 80 comprises separate microcontrollers for the rectifier stage 71 and the inverter stage 75, respectively.

[0082] The control unit 80 controls the active front end 72 via an AFE control signal 80a. The AFE control signal 80a may entail a pulse-width modulation for controlling switching frequencies of the active switches in the active front end 72.

[0083] The control unit 80 controls the inverter stage 75 via an inverter control signal 80b. The inverter control signal 80b may entail a pulse-width modulation for controlling switching frequencies of the active switches in the inverter stage 75.

[0084] It will be understood that although a single AFE control signal 80a and a single inverter control signal 80b are illustrated, in practice multiple control signals may be provided when multiple switches need to be controlled.

[0085] The control unit 80 is configured to control the frequency converter 70 (in particular the switching frequencies) such that the controllable frequency of the voltage of the transformed power is ((quasi-)stepless) adjustable between at least 400-1500 Hz (optionally between 1000-1500 Hz). This may be enabled by the high switching frequencies.

[0086] Since the transformed power 64 is generated using (digital) control with high frequency switches, the transformed power 64 will be stepped rather than having a waveform in a pure sine-shape. The system 2 comprises a (optionally passive) sine filter 76 to filter out harmonics. The passive sine filter 76 is a second order filter, which may be configured and designed to filter out harmonics of the voltage of the transformed power 64, when said transformed power has a frequency between 400-1500 Hz (optionally the best efficiency to filter harmonics when the transformed power has a frequency between 1000-1500 Hz) . The passive sine filter 76 generates a filtered power65 based on the transformed power. The filtered power 65 has a sine-shaped waveform having a total harmonic distortion of 1.41 + / -0.02%.

[0087] The system 2 further comprises an isolation transformer 77. The isolation transformer receives the filtered power 65 and has a power outlet 92. The power outlet 92 provides the electrical charge 41 to the stunner.

[0088] Fig. 2 further illustrates that the control unit 80 may receive an input signal 52a from the operator control panel 52. The operator can indicate input parameters on the operator control panel 52, based on which the input signal 52a is generated. The control unit 80 is configured to control the frequency and voltage of the transformed power 64 based on the input signal 52a. The inputs given by the operator may relate directly to a desired frequency and / or voltage. However, it is also possible that other input parameters are provided, from which the control unit 80 can derive a desired frequency and / orvoltage. Other configurations are also possible, for example a sensor system may be provided to generate an input signal and provide this to the control unit 80.

[0089] As required, detailed embodiments of the present invention are described herein; however, it is to be understood that the disclosed embodiments are merely examples of the invention, which may be embodied in various ways. Therefore, specific structural and functional details disclosed herein are not to be construed as limiting, but merely as a basis for the claims and as a representative basis for teaching those skilled in the art to practice the present invention in various ways in virtually any suitable detailed structure. Not all of the objectives described need be achieved with particular embodiments.

[0090] Furthermore, the terms and expressions used herein are not intended to limit the invention, but to provide an understandable description of the invention. The words “a”, “an”, or "one" used herein mean one or more than one, unless otherwise indicated. The terms "a multiple of", “a plurality” or "several" mean two or more than two. The words "comprise", "include", “contain” and "have" have an open meaning and do not exclude the presence of additional elements. Reference numerals in the claims should not be construed as limiting the invention.

[0091] The mere fact that certain technical features are described in different dependent claims still allows the possibility that a combination of these technical measures can be used advantageously.A single processor or other unit con perform the functions of various components mentioned in the description and claims, e.g. of processing units or control units, or the functionality of a single processing unit or control unit described herein can in practice be distributed over multiple components, optionally physically separated of each other. Any communication between components can be wired or wireless by known methods.

[0092] The actions performed by the control unit can be implemented as a program, for example computer program, software application, or the like. The program can be executed using computer readable instructions. The program may include a subroutine, a function, a procedure, an object method, an object implementation, an executable application, a source code, an object code, a shared library / dynamic load library and / or other set of instructions designed for execution on a computer system.

[0093] A computer program or computer-readable instructions can be stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied with or as part of other hardware, but can also be distributed in other forms, such as via internet or other wired or wireless telecommunication systems.

Claims

CLAIMS1. A system for supplying an electrical charge for stunning an animal, e.g. being poultry, the system comprising:• a power inlet configured to receive an input power;• a frequency converter configured to convert the input power into a transformed power;• a control unit configured to control the frequency converter, wherein the control unit is configured to control a switching frequency of the converter to generate the transformed power at a controllable frequency;• a sine filter configured to filter out harmonics of the voltage of the transformed power to provide a filtered power for providing the electrical charge, wherein the filtered power has voltage with a sineshaped waveform.

2. The system according to claim 1, wherein the animal is poultry.

3. The system according to claim 1 or claim 2, wherein the control unit and the frequency converter are configured to allow the switching frequency to reach 70 kHz or more, preferably 100 kHz or more, preferably 150 kHZ or more.

4. The system according to any of the preceding claims, wherein the sine filter is a passive sine filter.

5. The system according to claim 4, wherein the passive sine filter is a second order filter.

6. The system according to any of the preceding claims, wherein the frequency converter further comprises an active front end, e.g. in a rectifier stage, and preferably a filter for the active front end.

7. The system according to any of the preceding claims, wherein the system is configured to provide an output voltage having a waveform in a sine-shape, having a total harmonic distortion of 1.50 or less, e.g. 1.41 or less.

8. The system according to any of the preceding claims, wherein the control unit is configured to control the switching frequency such that the controllable frequency is adjustable, e.g. stepless adjustable, between at least 400-1500 Hz.

9. The system according to any of the preceding claims, wherein the frequency converter is a two-phase frequency converter.

10. The system according to any of the preceding claims, wherein the frequency converter is a SiC-based frequency converter.

11. The system according to any of the preceding claims, wherein the control unit is configured to receive an input signal, and control the frequency converter based on the input signal.

12. The system according to claim 11, further comprising a sensor system for detecting one or more characteristics of the animals to be stunned, wherein the sensor system is configured to generate the input signal.

13. The system according to claim 11 or claim 12, further comprising an operator input system configured to receive commands from an operator, wherein the operator input system is configured to generate the input signal based on a command of the operator.

14. A system for supplying an electrical charge for stunning an animal, being poultry, the system comprising: a power inlet configured to receive an input power; an active front end, optionally a filter for the active front end.

15. Stunning system, comprising a system for supplying an electrical charge according to any of the preceding claims, and a stunner configured to receive the electrical charge from said system and subject an animal to a potential difference based on said electrical charge.

16. Method for supplying on electrical charge for stunning an animal, e.g. being poultry, the method comprising:• receiving an input power;• converting the input power into a transformed power using a frequency converter;• controlling a switching frequency of the converter to generate the transformed power at a controllable frequency;• using a sine filter to filter out harmonics of the voltage of the transformed power to provide a filtered power having a voltage with a sine-shape waveform for providing the electrical charge.

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