Megawatt charging system charging test emulator

Abstract

An MCS charging test emulator is disclosed. The emulator comprises: a high-power transformer that converts field power to a voltage and capacity corresponding to test operation and provides isolation; a power conversion system that reproduces vehicle-side power behavior without directly using the battery and performs bidirectional charging and discharging control by integrating AC-DC, DC-DC, and DC-AC conversion functions; a measuring device that collects test data including voltage, current, temperature, and leakage current through high-speed sampling and records it in synchronization with communication events; an electric vehicle communication controller (EVCC) system that communicates with a charging station-side communication controller (SECC) and tests authentication, control, termination, and error recovery procedures; and a charging inlet and connector component comprising a vehicle-side inlet, a charger-side connector assembly, a cooling loop, a temperature sensor, and a current sensor as a physical connection interface compliant with MCS standards, wherein the components are synchronized by a central controller of the measuring device to experimentally verify the power response characteristics, communication reliability, and protection logic of the charger.

Description

Technology Field

[0001] The present invention relates to an MCS charging test emulator for testing a Megawatt Charging System (MCS) class ultra-high power charger at a charging station site. Background Technology

[0003] Heavy-duty commercial electric vehicles, such as large electric trucks and large electric buses, are equipped with batteries ranging from hundreds of kWh to several MWh, so the charging infrastructure scales up from hundreds of kW to several MW.

[0004] Recently proposed megawatt charging systems (MCS) include charger-side connector structures, cooling, communication, and security (e.g., ISO 15118-20, SPE 10BASE-T1S (Single Pair Ethernet), TLS (Transport Layer Security), PKI (Public Key Infrastructure)), and are based on ensuring interoperability between the charger and the vehicle.

[0005] However, consistently securing actual Megawatt Charging System (MCS)-class charging stations and large electric vehicles for testing is inefficient in terms of cost, safety, and repeatability. Furthermore, particularly in the domestic environment, the low accessibility of large electric trucks poses significant limitations to verification and regression testing during the early stages of development. Therefore, there is a need for an MCS charging test emulator that can quantitatively reproduce MCS conditions without actual batteries and verify field suitability by moving to a charging station. [Prior Art] Publication No.: 10-2025-0057275 Applicant: Chaebi Co., Ltd. Title of Invention: Electric Vehicle Charger Simulator The problem to be solved

[0007] The present invention, aimed at solving the aforementioned problems, aims to provide equipment for reliably verifying various algorithms and test cases of MCS-grade charging, and the specific objectives are as follows.

[0008] First, it is to provide equipment capable of replicating the MCS charging conditions of large commercial electric vehicles in a laboratory environment.

[0009] Second, the charging test is performed using a PCS (Power Conversion System)-based power source / sink that performs charging and discharging functions on behalf of the battery without actually using it.

[0010] Third, the goal is to establish a comprehensive test platform encompassing EV charging inlet connectors, EVCC (Electric Vehicle Communication Controller) communication modules, charging communication protocols, and electrical characteristics (voltage, current, ripple, responsiveness, etc.).

[0011] Fourth, it is to test various charging scenarios, such as rapid charging and communication error injection, while ensuring repeatability, stability, and scalability and reducing costs. means of solving the problem

[0013] An MCS charging test emulator for achieving the above-mentioned purpose comprises: a high-power transformer that converts field power into voltage and capacity corresponding to test operation and provides isolation; a power conversion system that reproduces vehicle-side power behavior without directly using the battery and performs bidirectional charging and discharging control by integrating AC-DC, DC-DC, and DC-AC conversion functions; a measuring device that collects test data including voltage, current, temperature, and leakage current through high-speed sampling and records it in synchronization with communication events; an electric vehicle communication controller (EVCC) system that communicates with a charging station-side communication controller (SECC) and tests authentication, control, termination, and error recovery procedures; and a charging inlet and connector component comprising a vehicle-side inlet, a charger-side connector assembly, a cooling loop, a temperature sensor, and a current sensor as a physical connection interface compliant with MCS standards, wherein the components are synchronized by a central controller of the measuring device to experimentally verify the power response characteristics, communication reliability, and protection logic of the charger.

[0014] In an embodiment, the power conversion system is characterized by being configured to receive a target voltage, maximum current, current ramp rate, constant current (CC) / constant voltage (CV) switching point, and allowable ripple conditions from a scenario file input by a tester, and to variably control the power output accordingly.

[0015] In an embodiment, the measuring device includes a test scenario execution, error injection control, and a remote monitoring interface, and is characterized by being configured to verify the error detection and recovery logic of the charger by artificially generating abnormal conditions such as communication packet loss, signal delay, Cyclic Redundancy Check (CRC) error, and current step distortion.

[0016] In an embodiment, the electric vehicle communication controller system is configured to verify the secure communication processing performance and interoperability of the charger by including a physical layer of Single Pair Ethernet 10BASE-T1S standard and an upper communication layer including Transport Layer Security (TLS) encryption and Public Key Infrastructure (PKI) certificates.

[0017] In the embodiment, the charging inlet and connector components include a liquid cooling loop to efficiently remove heat generated when a high output current is applied, and include a High Voltage Interlock Loop (HVIL) switch to immediately cut off the high voltage line when the connector is disconnected.

[0018] In an embodiment, the MCS charging test emulator is formed as a container-type structure that can be mounted on a mobile trailer, and is configured to perform a field test by connecting the output terminal and communication line of an external MCS charger after moving to a charging station site.

[0019] A method for testing MCS charging according to another aspect of the present invention comprises: (a) deploying an MCS charging test emulator at a charging station site and connecting power and ground; (b) establishing an ISO 15118-20 standard-based communication link between an electric vehicle communication controller system (EVCC) and a charger (SECC); (c) reproducing a CC-CV charging profile by controlling current, voltage, or output according to a tester's scenario by a power conversion system (PCS); (d) testing protection and recovery operations of a charger by a measuring device high-speed sampling of power and communication parameters and performing error injection; and (e) automatically generating a report of the test results to evaluate the power efficiency, response speed, communication recovery time, and protection logic characteristics of the charger.

[0020] In the embodiment, in step (b) above, the electric vehicle communication controller system sequentially performs authentication, a charging request, a charging control, a termination, and an error recovery procedure.

[0021] In the embodiment, in step (c), the power conversion system variably controls the power output based on the target voltage, maximum current, current ramp rate, and allowable ripple value input through a graphical user interface (GUI).

[0022] In the embodiment, error injection in step (d) includes communication packet loss, CRC error, and current step distortion, and verifies the charger's timeout, retransmission, and fail-safe procedures accordingly.

[0023] In an embodiment, the measuring device measures the DC link ringing frequency, the connector contact temperature rise rate, ripple RMS, and peak values ​​to generate time-axis-based analysis data.

[0024] In an example, the MCS charging test method places an emulator in series between the charger and the actual vehicle in an inline pass-through mode to non-invasively measure power flow and communication packets during actual charging and verify limit conditions. Effects of the invention

[0026] According to the present invention, repeatable testing is possible by reproducing MCS conditions at the level of large electric vehicles without an actual battery, and safety is improved by eliminating risk factors such as battery damage and thermal runaway. Power testing, encompassing charging, discharging, and V2G, and communication testing, including error injection, are implemented on a single platform, allowing for precise measurement of efficiency, ripple, response speed, dynamic control performance, communication responsiveness, and protection performance.

[0027] In addition, since the equipment is mounted on a truck (10) and moved to the charging station site, interoperability and field suitability in the actual installation environment can be verified early, which shortens the development period and allows for agile response to changes in standards and application conditions.

[0028] More specifically, since actual battery cells or modules do not need to be used, the risk of high battery damage and maintenance costs can be reduced, the same test conditions can be repeatedly implemented, and safety can be ensured by eliminating risk factors such as fire, heat generation, and lifespan degradation that may exist in the battery.

[0029] In addition, regarding flexible charging / discharging mode testing, not only simple charging but also discharging mode, power grid connection test, and reverse flow test (e.g., V2G concept test) are possible, and since it is possible to set various communication error scenarios and abnormal conditions for testing, various evaluations of the charging system are possible.

[0030] Furthermore, in terms of enhancing high-performance evaluation and verification capabilities, it is possible to precisely measure and evaluate power efficiency, ripple characteristics, response speed, dynamic control performance, communication responsiveness, and protection system performance, and it can be utilized for MCS standard interoperability testing, connector thermal characteristic testing, and communication compatibility testing.

[0031] Furthermore, in terms of shortening development time and market responsiveness, functionality can be verified in the early stages of development without securing actual large commercial electric vehicles or high-output charging stations, and it is possible to flexibly respond to changes in standard specifications or application conditions. Brief explanation of the drawing

[0033] FIG. 1 illustrates the concept of an exterior of an MCS charging test emulator according to an embodiment of the present invention and a truck equipped with it that moves to a charging station. Figure 2 is a schematic block diagram of the MCS charging test emulator of Figure 1. Specific details for implementing the invention

[0034] The terms used in this specification are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0035] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings. In order to facilitate an overall understanding of the present invention, the same reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0037] FIG. 1 illustrates the external appearance concept of an MCS charging test emulator according to an embodiment of the present invention and a mobile trailer equipped with it that moves to a charging station.

[0038] Referring to FIG. 1, the MCS charging test emulator (100) according to an embodiment of the present invention is configured within a test container (container-type enclosure) and is fixedly mounted on the cargo box or trailer of a mobile trailer (10), thereby facilitating movement to a charging station site. The mobile trailer (10) rapidly transports the container containing the MCS charging test emulator (100) to the charging station, and upon arrival at the destination, the MCS charging test emulator (100) is connected to the output terminal of an external MCS charger at the charging station via a communication line and is arranged to relay in series with an actual vehicle at the site if necessary (the relay function is omitted from illustration).

[0040] Figure 2 is a schematic block diagram of the MCS charging test emulator of Figure 1.

[0041] Referring to FIG. 2, the MCS charging test emulator (100) includes a high-power transformer (110), a power conversion system (PCS) (120), a measuring device (130), an electric vehicle communication controller (EVCC) system (140), and a charging inlet and connector component (150). Additionally, although not illustrated, the MCS charging test emulator (100) may further include a cooling system and a power distribution board, etc.

[0042] The above MCS charging test emulator (100) can test the withstand voltage characteristics of the charger under various field power conditions (e.g., voltage imbalance, frequency deviation, etc.) through the above high-power transformer (110).

[0043] In addition, the MCS charging test emulator (100) functions as a key test source for verifying the power control responsiveness and ripple suppression performance of the MCS charger through the PCS (120).

[0044] In addition, the MCS charging test emulator (100) can quantitatively record and analyze electrical abnormalities and communication events occurring during testing through the measuring device (130) to evaluate the fault tolerance of the charger.

[0045] In addition, the MCS charging test emulator (100) can use the EVCC system (140) to test the protocol interpretation capability, error recovery procedure, security authentication processing speed, etc. of the charger (SECC).

[0046] In addition, the physical durability and thermal stability of the MCS interface, such as contact heating, current imbalance, and connection stability, can be tested through the charging inlet and connector configuration (150) of the MCS charging test emulator (100).

[0047] The high-power transformer (110) converts the field power to a voltage and capacity suitable for test operation or emulator operation, and provides insulation to ensure a safety margin during high-power operation. Power system interfaces, such as busbars, circuit breakers, and distribution boards, are not shown but may be positioned between the secondary side of the high-power transformer (110) and the input terminal of the PCS (120) and designed to be immediately cut off in the event of overcurrent and ground fault. Here, a ground fault refers to a state in which the insulation of an electrical circuit is destroyed and current flows to the ground. In an embodiment, the high-power transformer (110) may be implemented as a dry-type structure (e.g., dry-type transformer) or an oil-immersed structure (e.g., oil-immersed transformer) depending on the power capacity and cooling conditions of the test environment, and is selected to meet the insulation class, cooling efficiency, and allowable temperature rise.

[0048] The above PCS (120) is a power converter that precisely reproduces vehicle-side power behavior without directly using a battery, and has a structure that integrates AC-DC, DC-DC, and DC-AC conversion functions for precise control. The above PCS (120) is equipped with a bidirectional charge / discharge function, which can reproduce various test conditions such as voltage, current waveform, ripple, response speed, and waveform distortion, and the output power capacity is configured from several hundred kW to a maximum of 1.25 MW or more, enabling the simulation of the power characteristics of a large MCS charger. The tester specifies a scenario including target voltage, maximum current, constant current (CC) and constant voltage (CV) switching points, current ramp rate, allowable ripple, and transient response target through a graphical user interface, and

[0049] The above PCS (120) operates according to the corresponding parameters and provides performance indicators such as voltage recovery time, current tracking, and power efficiency to the measuring device (130) along with a synchronization signal regarding changes in the charger's output. Additionally, if necessary, it absorbs power in a discharge (sink) mode to perform a Vehicle-to-Grid (V2G) concept test, and regenerates power by returning it to the grid or consuming it as a dummy load (the grid connection part is omitted from the drawing).

[0050] The above measuring device (130) is configured as a control and monitoring system that simultaneously performs real-time measurement of power and communication characteristics and central control functions. The measuring device (130) includes a central controller (Programmable Logic Controller: based on PLC or MCU / FPGA) to collect various sensor data such as voltage, current, temperature, and leakage current using high-speed sampling, and stores them by matching them with communication logs and timestamps. For example, the DC-link ringing frequency at the moment a current step is applied, the connector contact temperature rise rate (temperature sensor linkage is omitted from the illustration), and leakage current monitoring results can be grouped into a single timeline for analysis, thereby clearly confirming the causal relationship between electrical characteristics and communication and protection events. In addition, the measuring device (130) provides functions for test scenario execution, error injection control, remote monitoring, and control interfaces (including PC GUI and network connection), thereby supporting the tester to adjust each condition in real time and visually analyze the results. Here, Error Injection control refers to a function that verifies the error detection and recovery logic of a charger by intentionally generating abnormal conditions such as communication packet loss, signal delay, CRC (Cyclic Redundancy Check) errors, and current step distortion. Through this, the tester can quantitatively evaluate the fault tolerance and recovery capability of the charging system in both normal and abnormal operating situations. Here, the current step distortion refers to a phenomenon in which, when the current control signal changes instantaneously, the actual current response does not follow an ideal step shape but is non-linearly deformed by control delay, voltage saturation, LC resonance, etc., inside the power converter.In an embodiment, the central controller of the measuring device synchronizes the signals collected from the PCS (120), EVCC system (130), and inlet / connector component (150) to the same time base and orchestrates the operation of each component according to a test scenario.

[0051] The EVCC system (140) is an emulator that simulates the operation of a vehicle-side communication controller and is responsible for communication with an external MCS charger (Supply Equipment Communication Controller: SECC) on the charging station side. The EVCC system (140) sequentially performs the procedures of establishing a charging session, charging request, authentication, charging control, and termination according to the ISO 15118-20 standard, and can verify communication behavior including error handling and restoration procedures in the event of a charger response anomaly or a communication error. More specifically, the EVCC system (140) can monitor message exchange and state transitions at each stage. The physical layer of communication is implemented based on the Single Pair Ethernet (SPE) 10BASE-T1S standard, and at the upper layer, encrypted communication using the Transport Layer Security (TLS) protocol and certificate exchange based on Public Key Infrastructure (PKI) are performed. Through this hierarchical communication structure, the EVCC system (140) can precisely reproduce the communication behavior of the actual vehicle and evaluate interoperability indicators with the charger, security policies, error recovery procedures, etc. As such, the emulator according to the present embodiment can quantitatively evaluate indicators including communication reliability and interoperability.

[0053] The charging inlet and connector assembly (150) is implemented as a connection interface that complies with actual Megawatt Charging System (MCS) specifications. The assembly (150) includes a vehicle inlet, a charging cable and connector assembly, and a temperature and contact resistance monitoring sensor module. The vehicle inlet is designed to safely transmit currents ranging from hundreds of kW to several MW using copper alloy or plated aluminum conductors, and the insulator is formed from a flame-retardant composite resin material with arc-prevention performance. The connector assembly is mechanically coupled to the charging station-side MCS plug and is designed to maintain a constant current path, contact resistance, and temperature distribution in the connected state. A temperature sensing sensor and a current sensor (e.g., a Hall Current Sensor) are embedded in the connection surface to detect overheating or abnormal current flow at the connector contacts in real time.

[0054] Additionally, the inlet and connector components (150) include a liquid cooling loop or an air cooling fan system to efficiently remove heat generated when a high-output current is applied. The cooling loop is equipped with cooling water inlet and outlet ports, and the cooling efficiency can be automatically controlled by a heat exchanger and a temperature sensor installed inside. A High Voltage Interlock Loop (HVIL) switch is provided at the connector connection part to ensure user safety by immediately cutting off the high-voltage line when the connector is disconnected.

[0055] The above inlet and connector configuration (150) includes a data communication line (Twisted Pair Communication Line) with the charger-side SECC (Supply Equipment Communication Controller) and is synchronized with the EVCC (140) to enable real-time monitoring of data exchange, error detection, and security status based on the ISO 15118 protocol. With this configuration, the charging inlet and connector configuration (150) performs the function of testing and verifying problems such as current imbalance, contact heating, and communication interference that may occur in an MCS charging environment, and can reproduce conditions identical to those of an actual commercial large-scale electric vehicle charging system in a laboratory environment.

[0057] Hereinafter, the operation of the MCS charging test emulator according to an embodiment of the present invention will be described.

[0058] The test begins from the moment the emulator (100) arrives at the charging station on a mobile trailer (10). After securing the equipment and checking the grounding status, the cooling system is activated to secure thermal equilibrium, and then the tester loads the scenario file and reviews the target profile. During this process, the EVCC system (140) and PCS (120) perform an initialization routine to transition to a state ready for communication and power control.

[0059] First, the EVCC system (140) establishes a link with the charger and forms a secure channel, and then exchanges and sets parameters such as maximum voltage / current, power level, and termination condition. Once the parameter setting procedure is completed, the PCS (120) ramps up the current, voltage, or output to gradually increase it to enter a designated constant current (CC) level, controls the charger output voltage to minimize the difference between the PCS terminal voltage and the charger output voltage, and automatically switches to a constant voltage (CV) level when the target voltage is reached. At this time, the measuring device (130) records the Root Mean Square (RMS) of the ripple voltage, the settling time of the peak and step response, output efficiency, and the ratio of active and reactive power as measurement data along the time axis.

[0060] Subsequently, the tester enters a stress phase and artificially induces communication delays or packet loss to verify whether the charger performs command retransmission, timeouts, and fail-safe procedures. Transient response characteristics are tested by rapidly increasing or decreasing the current, and hysteresis and recovery conditions of the protection logic are measured by repeatedly inducing overvoltage / overcurrent protection conditions near boundary values. In addition, the ride-through performance of the charger is evaluated by reproducing grid distortion scenarios, such as voltage dips, harmonics, and frequency fluctuations, in conjunction with a power grid simulator (not shown).

[0061] When the test ends, the EVCC system (140) transmits a normal shutdown command, and the PCS (120) attenuates the current to cut off the output. If a discharge test is included, the emulator switches to sink mode to return the stored energy to the grid or consume it as an internal load. During this process, an automatic shutdown procedure is executed when an emergency shutdown condition or an anomaly is detected to ensure the safety of the equipment.

[0062] Once all measurement data and communication history are stored, an analyzer (not shown) within the measuring device (130) automatically generates a report, and the generated report includes power efficiency curves, ripple spectrum, response delay distribution, recovery time upon error injection, protection event trigger sequence, communication compatibility indicators, etc. Based on the results, the tester can re-verify the response characteristics of the charger by repeating the scenario or changing the parameters.

[0063] Meanwhile, the MCS charging test emulator according to an embodiment of the present invention provides two test operation modes. In the basic vehicle-side emulation mode, the emulator directly receives and consumes the charger output power while measuring all power parameters and communication parameters. In the optional inline pass-through mode, the emulator (100) is relayed in series between the charger and a commercial large electric vehicle to non-invasively measure power flow and communication packets during actual charging, and, if necessary, apply a small error to verify limit conditions (relay hardware is omitted).

[0065] The embodiments disclosed in this specification should be considered in an exemplary sense for the sake of illustration rather than in a limiting sense. The scope of the invention is defined by the claims, not by the foregoing description, and all variations within the scope of the claims should be interpreted as being included in the invention.

Claims

Claim 1 In an MCS charging test emulator for testing the power and communication characteristics of a Megawatt Charging System (MCS) charger, the system comprises: a high-power transformer that converts field power to a voltage and capacity corresponding to test operation and provides isolation; a power conversion system that reproduces vehicle-side power behavior without directly using a battery and performs bidirectional charging and discharging control by integrating AC-DC, DC-DC, and DC-AC conversion functions; a measuring device that collects test data including voltage, current, temperature, and leakage current through high-speed sampling and records it in synchronization with communication events; and an Electric Vehicle Communication Controller (EVCC) system that communicates with a Charging Station-side Communication Controller (SECC) and tests authentication, control, termination, and error recovery procedures. An MCS charging test emulator characterized by comprising a charging inlet and connector component including a vehicle-side inlet, a charger-side connector assembly, a cooling loop, a temperature sensor, and a current sensor as a physical connection interface compliant with MCS standards, wherein the components are synchronized by a central controller of the measuring device to experimentally verify the power response characteristics, communication reliability, and protection logic of the charger, and wherein the measuring device includes a test scenario execution, error injection control, and remote monitoring interface, and is configured to verify the error detection and recovery logic of the charger by artificially generating abnormal conditions such as communication packet loss, signal delay, Cyclic Redundancy Check (CRC) error, and current step distortion. Claim 2 An MCS charging test emulator according to claim 1, characterized in that the power conversion system is configured to receive target voltage, maximum current, current ramp rate, constant current (CC) / constant voltage (CV) switching point, and allowable ripple conditions from a scenario file input by a tester, and accordingly, variably control the power output. Claim 3 delete Claim 4 In claim 1, the electric vehicle communication controller system is characterized by being configured to verify the secure communication processing performance and interoperability of a charger by including a physical layer of Single Pair Ethernet 10BASE-T1S standard and an upper communication layer including Transport Layer Security (TLS) encryption and Public Key Infrastructure (PKI) certificates. Claim 5 The MCS charging test emulator according to claim 1, characterized in that the charging inlet and connector components include a liquid cooling loop to efficiently remove heat generated when a high output current is applied, and include a High Voltage Interlock Loop (HVIL) switch to immediately cut off the high voltage line when the connector is disconnected. Claim 6 In claim 1, the MCS charging test emulator is characterized by being formed as a container-type structure that can be mounted on a mobile trailer, and configured to perform a field test by connecting the output terminal and communication line of an external MCS charger after moving to a charging station site. Claim 7 A method for testing the power, communication, and protection performance of a megawatt charging system (MCS) charger, comprising: (a) deploying an MCS charging test emulator at a charging station site and connecting power and ground; (b) establishing an ISO 15118-20 standard-based communication link between an electric vehicle communication controller system (EVCC) and a charger (SECC); (c) reproducing a CC-CV charging profile by controlling current, voltage, or output according to a tester's scenario by a power conversion system (PCS); (d) demonstrating the protection and recovery operations of the charger by a measuring device high-speed sampling of power and communication parameters and performing error injection; and (e) automatically generating a report of the test results by the measuring device to evaluate the power efficiency, response speed, communication recovery time, and protection logic characteristics of the charger. Claim 8 In claim 7, the MCS charging test method is characterized in that, in step (b) above, the electric vehicle communication controller system sequentially performs authentication, charging request, charging control, termination, and error recovery procedures. Claim 9 In claim 7, the MCS charging test method is characterized in that, in step (c) above, the power conversion system variably controls the power output based on the target voltage, maximum current, current ramp rate, and allowable ripple value input through a graphical user interface (GUI). Claim 10 In claim 7, the MCS charging test method is characterized in that, in step (d) above, error injection includes communication packet loss, CRC error, and current step distortion, and verifies the charger's timeout, retransmission, and fail-safe procedures accordingly. Claim 11 In claim 7, the MCS charging test method is characterized in that the measuring device measures the DC link ringing frequency, the connector contact temperature rise rate, the ripple RMS, and the peak value to generate time-axis-based analysis data. Claim 12 In claim 7, the MCS charging test method is characterized by serially placing an emulator between a charger and an actual vehicle in an inline pass-through mode to non-invasively measure power flow and communication packets during actual charging and verify limit conditions.

Images