Charging system

Technical Field

[0001] The invention relates to a charging system configured for providing

electrical energy to charge a battery of an electrical vehicle with a charging current l _c , comprising an overcurrent protection device characterized by a breaking current lb switching off the overcurrent protection device.

Background Art

[0002] Charging systems for providing electrical energy to charge a battery of an electrical vehicle are known from prior art. Said charging systems are usually connected on an AC side with a power source such as an AC grid and comprise on a DC side a plurality of charging ports providing charging current. Each charging port comprises an interface for energy exchange between the charging system and the electrical vehicle via a cable. The cable as well as other cables provided in the charging system are normally protected by fuses on the battery side and a limited current on the charger side, provided for example as fuses on the DC side and/or as fuses on the AC side of the charging system. If a short circuit occurs when charging the electrical vehicle the fuse in the electrical vehicle will break if the short circuit current is large enough. As the fuse in the electrical vehicle is hard to reach replacing a broken fuse is laborious and costly.

[0003] In practise, the let through energy of the fuse is often chosen very high, for example 12 MA ² s, compared to the expected charging current required for charging the electrical vehicle. When an overcurrent occurs for example by a weak short circuit or a malfunction of the charger system, the

overcurrent can be detected and the charging should be interrupted by an electrically controlled switch arranged in the charging path of the charging current. Electrically controlled switches, however, have a limited breaking capacity. If the breaking capacity is exceeded the electrically controlled switch can be destroyed. Replacing a destroyed electrically controlled switch is much more costly than replacing a broken fuse . Summary of invention

[0004] It is therefore an object of the invention to provide a system and a method for protecting an electrically controlled switch of a charging system for providing electrical energy to charge a battery of an electrical vehicle.

[0005] The object of the invention is solved by the features of the independent claims. Preferred embodiments are described in the dependent claims.

[0006] Thus, the object is solved by a charging system configured for providing electrical energy to charge a battery of an electrical vehicle with a charging current l _c , whereby the charging system is characterized by a nominal current I N, comprising an overcurrent protection device characterized by a breaking current lb switching off the overcurrent protection device, whereby lb≥ I N, an electrically controlled switch characterized by switching a maximum switching current I max, and a control device in electrical connection with at least the electrically controlled switch, whereby the electrically controlled switch and the overcurrent protection device are connected in series and arranged in the current path of the charging current l _c , and the control device is configured for switching off the electrically controlled switch at a time t > 0 after the charging current l _c has exceeded the nominal current I N or after the overcurrent protection device has switched off due to the charging current l _c has exceeded the breaking current lb.

[0007] A key point of the invention is therefore to let the overcurrent protection device switch off an overcurrent resulting for example from a malfunction if the overcurrent is larger than the nominal current I N, and thereafter, once the overcurrent protection device has switched off, first to wait the time t > 0 and then second to switch off the electrically controlled switch. If the overcurrent protection device has not switched off within the time t = l ² t/lb ² , a fault current is below l _m ax and the electrically controlled switch can break the charging current l _c . Therefore, the breaking capacity of the overcurrent protection device is chosen higher than of the electrically controlled switch. In such was it is ensured that the breaking capacity of the electrically controlled switch is never exceeded i.e. that the electrically controlled switch cannot be destroyed by an overcurrent. In other words, to prevent fusing the electrically controlled switch the idea is to wait for the

overcurrent protection device to blow before opening the electrically controlled switch, at the time t after the overcurrent protection device has blown. In this way the electrically controlled switch is prevented against damage occurred by an overcurrent. The term overcurrent may relate to an overcurrent, a short circuit, a fault and/or a malfunction of the charging system and thereto connected devices such as the electrical vehicle, a cable connecting the charging system and the electrical car, a power grid or the like.

[0008] An electrical vehicle, abbreviated as EV and as also referred to as an

electric drive vehicle or electric vehicle, uses one or more electric motors or traction motors for propulsion. EVs may include road and rail vehicles, surface and underwater vessels, electric aircraft and electric spacecraft. The term opening or switching off respectively closing or switching on means that an electrical connection is interrupted respectively established, for example by the overcurrent protection device or the electrically controlled switch. The term maximum switching current l _max is to be understood as the maximum current that can be switched by the

electrically controlled switch with destroying or damaging the electrically controlled switch, for example as the designed load current per contact of the electrically controlled switch. The breaking current lb is to be

understood as the current which causes the overcurrent protection device to switch off. The battery is preferably provided as a DC battery.

[0009] According to a preferred embodiment, the control device is configured for measuring the charging current l _c and for switching off the electrically controlled switch if the charging current l _c has exceeded the nominal current IN or the breaking current lb. Preferably the control device comprises an ammeter arranged in the current path for measuring the charging current l _c . It can be possible to measure the charging current l _c within the electrical vehicle for example directly at the battery of the electrical vehicle, at the cable connecting the electrical vehicle with a charging device provided within the charging system. Switching off the electrically controlled switch can be done, for example, by sending a switching signal from the control device to the electrically controlled switch.

[0010] According to another preferred embodiment, the overcurrent protection device is characterized by a let through energy l ² t and the time t is the let through energy l ² t divided by the square of the breaking current lb, t = ! ² t/lb ² . Thus, for example, if l ² t equals 120 kA ² s and the breaking current lb equals 200 A then the time t is 3 seconds. The let through energy l ² t, ampere squared seconds, is to be generally understood as an expression related to a circuit energy as a result of a current. With respect to an overcurrent protection device respectively a circuit breaker, the let through energy l ² t is preferably expressed for the current flow between an initiation of a fault current and clearing of the overcurrent protection device respectively the circuit breaker. Waiting said time t = l ² t/lb ² has been proven as very advantageous for protecting the electrically controlled switch against damage due to an overcurrent.

[001 1] According to another preferred embodiment, the charging system

comprises the electrical vehicle and a charging device configured for charging the electrical vehicle, whereby the electrical vehicle and/or the charging device comprises the overcurrent protection device and the charging device comprises the electrically controlled switch and the control device. The charging device is preferably provided as a DC charger with, for example, 50kW DC fast charging capability thus allowing a typical charging of 30 to 80% in 15 minutes at an output voltage of 200-500 V at 125 A (Combo-1 ) or 50-500 V at 120 A (CHAdeMO) and/or may fulfil EN61851 -23 / DIN 70121 Combo-1 and/or CHAdeMO 1.0 DC connection standards for a charging port.

[0012] According to another preferred embodiment, the electrically controlled

switch and the overcurrent protection device are connected in series between the electrical vehicle and the charging device. Preferably, the electrically controlled switch and the overcurrent protection device are provided within an enclosure of the charging device. [0013] According to another preferred embodiment, the charging system comprises a cable configured for electrically connecting the electrical vehicle and the charging device for conducting the charging current l _c . The cable my comprise connectors for connecting to the electrical vehicle and an interface of a charging port of the charging device.

[0014] According to another preferred embodiment, the electrically controlled witch is provided as a contactor. A contactor is an electrically controlled switch for switching an electrical power circuit and is often controlled by a circuit which has a lower power level than the switched circuit.

[0015] According to another preferred embodiment, the overcurrent protection device is provided as a fuse or as a circuit breaker and/or the overcurrent protection device is characterized by a current time graph, whereby the time t corresponds to the breaking current lb. A circuit breaker is an automatically operated electrical switch designed to protect the electrical circuit formed by the charging system from damage caused by overcurrent or overload or short circuit. Once the charging current l _c has exceeded the nominal current IN or the breaking current lb, the circuit breaker interrupts respectively switches off the current path of the charging current l _c after protective relays of the circuit breaker have detected the fault. The fuse works in an analogue manner, but comprises a metal wire or strip that melts when to much current flows through it thereby interrupting the current path of the charging current l _c .

[0016] According to another preferred embodiment, the charging system

comprises a plurality of power converters configured for converting electrical energy from a power source such as a power grid to a suitable format for charging the electrical vehicle. According to another preferred embodiment, the plurality of power converters each have an AC side configured for connecting to the power source and an DC side configured for providing electrical energy to the battery of the electrical vehicle, whereby the overcurrent protection device is arranged on the AC side and/or on the DC side of the plurality of power converters. The power converter is preferably configured for converting AC power from the power source connected to the AC side to suitable DC format for charging the electrical vehicle at the DC side.

[0017] According to another preferred embodiment, the overcurrent protection device, the electrically controlled switch and/or the control device comprise a communication device configured for exchanging information regarding breaking current lb, maximum switching current I max, let through energy l ² t, charging current l _c and/or time t with at least the electrical vehicle.

Preferably, such control device is installed at each of the overcurrent protection device, the electrically controlled switch, the control device and the electrical vehicle, thereby allowing an easy exchange of said information.

[0018] According to another preferred embodiment, the charging system

comprises a plurality of charging ports each comprising an interface for energy exchange with at least one electrical vehicle. The charging port, also referred to as an outlet, may comprise a JARI Level 3 DC connector as interface. According to a further preferred embodiment, the maximum switching current I max is greater than the breaking current lb.

[0019] The object of the invention is further solved by a method for protecting an electrically controlled switch when charging a battery of an electrical vehicle with a charging current l _c , whereby the charging system is characterized by a nominal current IN, comprising an overcurrent protection device characterized by a breaking current l b switching off the overcurrent protection device, whereby lb≥ IN, and the electrically controlled switch characterized by switching a maximum switching current I max, whereby the electrically controlled switch and the overcurrent protection device are connected in series and arranged in the current path of the charging current l _c , comprising the steps of:

detecting, if the charging current l _c has exceeded the nominal current IN or if the overcurrent protection device and has switched off due to the charging current l _c has exceeded the breaking current lb, and

in such case switching off the electrically controlled switch at a time t > 0 after the charging current l _c has exceeded the nominal current IN or after the overcurrent protection device has switched off. [0020] A key point of the method is therefore to protect the electrically controlled switch from damage or destruction to an overcurrent by waiting for the overcurrent protection device to switch off as a result of the overcurrent and thereafter to open the electrically controlled switch, at the time t after the overcurrent protection device has switched-off. The overcurrent occurs if the charging current l _c exceeds the nominal current IN thereby causing the overcurrent protection device to switch off.

[0021] According to a further preferred embodiment, the overcurrent protection device is characterized by a let through energy l ² t and the time t is the let through energy l ² t divided by the square of the breaking current lb, t = I .

[0022] Further embodiments and advantages of the method are directly and

unambiguously derived by the person skilled in the art from the system as described above.

Brief description of drawings

[0023] These and other aspects of the invention will be apparent from and

elucidated with reference to the embodiments described hereinafter.

[0024] In the drawings:

[0025] Fig. 1 shows a charging system according to preferred embodiment of the invention in a schematic view.

Description of embodiments

[0026] Fig. 1 shows a charging system according to preferred embodiment of the invention in a schematic view comprising a plurality of power converters 1 i.e. three power converters 1 , which are each configured for converting electrical energy from a power source 2, such as a power grid, to a suitable format for charging an electrical vehicle 3.

[0027] Each power converter 1 comprises an AC side 4, which is connected to the power source 2, and an DC side 5, which is connected to a charging device 6. While Fig. 1 shows only one charging device 6, multiple charging devices 6 can be present and connected to one or more of the power converters 1. As shown in the figure, the charging device 6 is electrically connected to two power converters 1. The term connected is to be understood as electrically connected.

[0028] The charging device 6 comprises an overcurrent protection device 7, an electrically controlled switch 8 and a control device 9. The overcurrent protection device 7 and the electrically controlled switch 8 are arranged in series between the power converters 1 connected to the charging device 6 and a DC cable 10, which connects a DC battery 1 1 of the electrical vehicle 3 with the charging device 6 for conducting a charging current l _c . In this way the overcurrent protection device 7 and the electrically controlled switch 8 are arranged in the current path of the charging current l _c . A likely source of an overcurrent is a battery of the electrical vehicle 3.

[0029] The charging device 6 further comprises a plurality of charging ports 12 for connecting the DC cable 10, whereby each charging port 1 1 comprises an interface 13 such as a jack. A current rating of the charging device 6 is less or equal to a current rating of charging ports 12 respectively interface 13. In an alternate not shown embodiment the overcurrent protection device 7 can be arranged on the AC side 4 or a plurality of overcurrent protection devices 7 can be arranged both on the AC side 4 and on the DC side 5.

[0030] The overcurrent protection device 7 is provided as a fuse or as a circuit breaker and is characterized by a breaking current lb and by a let through energy l ² t. If the charging current l _c exceeds the breaking current lb the overcurrent protection device 7 switches off i.e. "blows" and thus interrupts the charging of the electrical vehicle 3. The electrically controlled switch 8 is provided as a contactor and is characterized by a maximum switching current I max, which is greater than the breaking current lb.

[0031] The control device 9 is in electrical connection with the overcurrent

protection device 7 and the electrically controlled switch 8. In this way the overcurrent protection device 7, the electrically controlled switch 8, the electrical vehicle 3 and the control device 9 each comprise a communication device 14, which is configured for exchanging information regarding the breaking current lb, the maximum switching current I max, the let through energy l ² t, the charging current l _c and a time t explained below.

[0032] If the charging current l _c exceeds the breaking current lb, first the

overcurrent protection device 7 switches off. The control device 9 is configured for switching off the electrically controlled switch 8 at the time t > 0 after the overcurrent protection device 7 has switched off or after the charging current l _c has exceeded a nominal current IN of the charging system respectively charging device 6. Therefore, the control device 9 is configured to measure the charging current l _c . The time t is calculated by the control device 9 as the let through energy l ² t of the overcurrent protection device 7 divided by the square of the breaking current lb i.e. as t = I .

[0033] Thus, in order to prevent fusing of the electrically controlled switch 8 due to an overcurrent or a malfunction the control device 9 first "waits" until the overcurrent protection device 7 switches off and second, at the timespan t thereafter, opens respectively switches off the electrically controlled switch 8. For example, with l ² t = 120 kA ² s and lb = 200 A, the time t is 3 seconds. Thus, with the present example, if an overcurrent has occurred e.g. if the charging current l _c has exceeded the breaking current lb, the overcurrent protection device 7 switches off and thereby interrupts the charging of the electrical vehicle. 3 second thereafter, the control device 9 causes the electrically controlled switch 8 to switch off. Thereby, the electrically controlled switch 8 is protected from breaking due to the overcurrent.

[0034] While the invention has been illustrated and described in detail in the

drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to be disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting scope.

Reference signs list

[0035] 1 power converter

2 power source

3 electrical vehicle

4 AC side

5 DC side

6 charging device

7 overcurrent protection device

8 electrically controlled switch

9 control device

10 cable

1 1 battery

12 charging port

13 interface

14 communication device