lectric system safety: Protection against electric shocks
Voltage levels on board electric vehicles
Typical voltage levels on electric vehicles are as follows:
• 48-120 V for cars and small vans
• 96-240 V for large vans
• 300-600 V for buses
For AC drives, which are gaining an increasing popularity, higher voltage levels are
used; 200 V or more may be encountered even on small vehicles.
These voltage levels are to be compared with the safety voltage levels: in a typical
electric vehicle environment, characterised by a low skin resistance (wet skin likely)
(BB2) and a contact with conductive bodies (BC3), the security extra low voltage
level is 25 V for AC and 60 V for DC.
The voltages used on electric vehicles are thus potentially dangerous and measures
should be taken to prevent electrocution through direct or indirect contact.
Protection against direct contact
Live parts of the electric traction system should be protected against direct contact by
persons in or outside the vehicle, through insulation or inaccessible position.
Insulation such as varnish, enamel, coatings,… are not considered to be insulation as
required for protection against direct contact.
Removal of protective devices and opening of doors, lids, and bonnets permitting
access to live electrical equipment shall only be possible with tools or keys..
The conventional protection degrees (IPXXB or IPXXD) should be enforced:Protection against indirect contact
The problem of indirect contacts is closely related to the problem of frame faults.
Any spurious connection between the traction circuit and the vehicle frame is
regarded as a fault. Frame faults can lead to several hazards:
• short circuits
• electrocution
• uncontrolled operation
Following measures should be taken to avoid these hazards:
• a fuse shall be built inside the battery pack, preferably in the electrical centre of
the battery
• the vehicle frame shall be isolated from the traction circuit and shall not form
any part of the power electrical circuit
• all conductive parts of the vehicle, particularly accessible parts or parts adjacent
to electrical equipment shall be connected with an equipotential connection.
• frame fault leakage detection shall be included in routine maintenance;
permanent frame fault monitoring is mandatory for certain vehicles.
Functional system safety
The electric vehicle traction system must ensure a reliable and safe operation of the
vehicle.
The topology of the traction system in an electric vehicle is fundamentally different
from IC-engined vehicles and specific measures should be taken to avoid or prevent
unsafe operations.
System activation warning
An electric vehicle standing still is in most cases completely silent. To prevent
movement through unintentional actuating of the traction circuit, a warning device
shall be present.
Power on procedure
To avoid possible damage through excessive torque, overcurrent or fierce
accelerations, the power on procedure must be adequately organised: it shall be
impossible to activate the controller with the accelerator depressed. Any
unintentional movement of the vehicle during start-up shall be avoided.
Driving backwards - Prevention of fierce reverse braking
The change of driving direction in an electric vehicle can be done mechanically or
electricallyIn the latter case, the actuation of the reversing shall be obtained by two different;
consecutive movements or an electrical safety device which only allows reverse to
be engaged when the vehicle speed is lower than 1 m/s, in which case actuation of
the control unit shall be indicated obviously.
Emergency disconnect device
This problem is approached in a different way by car manufacturers and electricians:
• vehicle manufacturers do not consider emergency switches as a necessity and
want to avoid them (they are in fact not present on thermal vehicles)
• electrical manufacturers consider emergency switches as essential (they are in fact
present on any industrial electric device)
Emergency switches come in different versions:
• battery connectors
• direct-acting emergency buttons
• indirect-acting emergency buttons
It is recommendable that the disconnect action is direct.
Furthermore, its operation shall not be detrimental to the controller.
Fail-safe operation- Power surge prevention
Unintentional acceleration due to failures in electronic traction controllers must be
prevented by the use of power surge control fail-safe circuitry. In particular, any
failure shall not cause more than 0,1 m movement of a standing, unbraked vehicle.
Fail-safe operation - Frame faults
Frame faults and stray currents can also cause uncontrolled oper
lectric ระบบความปลอดภัย: ป้องกันไฟฟ้าระดับแรงดันไฟฟ้าบนยานพาหนะไฟฟ้าระดับแรงดันไฟฟ้าทั่วไปในยานพาหนะไฟฟ้าดังต่อไปนี้:• 48-120 V สำหรับรถยนต์และรถตู้ขนาดเล็ก• 96-240 V สำหรับรถตู้ขนาดใหญ่• 300-600 V สำหรับรถบัสสำหรับ AC ไดรฟ์ ที่กำลังได้รับความนิยมที่เพิ่มขึ้น เป็นระดับแรงดันไฟฟ้าที่สูงขึ้นใช้ 200 V หรือมากกว่าอาจพบแม้ในยานพาหนะขนาดเล็กระดับแรงดันไฟฟ้าเหล่านี้จะเทียบเคียงกับระดับแรงดันไฟฟ้าความปลอดภัย: ในทั่วไปยานพาหนะไฟฟ้าสิ่งแวดล้อม ลักษณะความต้านทานผิวต่ำ (เปียกผิวแนวโน้ม)(BB2) และติดต่อกับร่างกายเป็นตัวนำไฟฟ้า (BC3), แรงดันไฟฟ้าต่ำพิเศษความปลอดภัยระดับคือ 25 V สำหรับ AC และ 60 V สำหรับ DCแรงดันไฟฟ้าที่ใช้ในยานพาหนะไฟฟ้ากำลังดังนั้นอาจเป็นอันตราย และมาตรการจะต้องดำเนินการป้องกันไม่ให้ไฟฟ้าผ่านการติดต่อทางตรง หรือทางอ้อมป้องกันการติดต่อโดยตรงสดส่วนของระบบไฟฟ้าลากควรจะป้องกันการติดต่อโดยตรงโดยคนใน หรือภาย นอก รถ ฉนวนกันความร้อนหรือไม่สามารถเข้าถึงตำแหน่งฉนวนกันความร้อนเคลือบเงา เคลือบ เคลือบ,...จะไม่ถือว่าเป็นฉนวนกันความร้อนเป็นจำเป็นสำหรับการป้องกันการติดต่อโดยตรงกำจัดป้องกันอุปกรณ์และ เปิดประตู ฝา bonnets ที่เอื้ออำนวยเข้าถึงสดอุปกรณ์ไฟฟ้าจะสามารถทำได้ ด้วยเครื่องมือหรือปุ่ม...องศาการป้องกันทั่วไป (IPXXB หรือ IPXXD) ควรมีผลบังคับใช้: ป้องกันการติดต่อทางอ้อมThe problem of indirect contacts is closely related to the problem of frame faults.Any spurious connection between the traction circuit and the vehicle frame isregarded as a fault. Frame faults can lead to several hazards:• short circuits• electrocution• uncontrolled operationFollowing measures should be taken to avoid these hazards:• a fuse shall be built inside the battery pack, preferably in the electrical centre ofthe battery• the vehicle frame shall be isolated from the traction circuit and shall not formany part of the power electrical circuit• all conductive parts of the vehicle, particularly accessible parts or parts adjacentto electrical equipment shall be connected with an equipotential connection.• frame fault leakage detection shall be included in routine maintenance;permanent frame fault monitoring is mandatory for certain vehicles.Functional system safetyThe electric vehicle traction system must ensure a reliable and safe operation of thevehicle.The topology of the traction system in an electric vehicle is fundamentally differentfrom IC-engined vehicles and specific measures should be taken to avoid or preventunsafe operations.System activation warningAn electric vehicle standing still is in most cases completely silent. To preventmovement through unintentional actuating of the traction circuit, a warning deviceshall be present.Power on procedureTo avoid possible damage through excessive torque, overcurrent or fierceaccelerations, the power on procedure must be adequately organised: it shall beimpossible to activate the controller with the accelerator depressed. Anyunintentional movement of the vehicle during start-up shall be avoided.Driving backwards - Prevention of fierce reverse brakingThe change of driving direction in an electric vehicle can be done mechanically orelectricallyIn the latter case, the actuation of the reversing shall be obtained by two different;consecutive movements or an electrical safety device which only allows reverse tobe engaged when the vehicle speed is lower than 1 m/s, in which case actuation ofthe control unit shall be indicated obviously.Emergency disconnect deviceThis problem is approached in a different way by car manufacturers and electricians:• vehicle manufacturers do not consider emergency switches as a necessity andwant to avoid them (they are in fact not present on thermal vehicles)• electrical manufacturers consider emergency switches as essential (they are in factpresent on any industrial electric device)Emergency switches come in different versions:• battery connectors• direct-acting emergency buttons• indirect-acting emergency buttonsIt is recommendable that the disconnect action is direct.Furthermore, its operation shall not be detrimental to the controller.Fail-safe operation- Power surge preventionUnintentional acceleration due to failures in electronic traction controllers must beprevented by the use of power surge control fail-safe circuitry. In particular, anyfailure shall not cause more than 0,1 m movement of a standing, unbraked vehicle.Fail-safe operation - Frame faultsFrame faults and stray currents can also cause uncontrolled oper
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