The main difference between high and low voltage connectors in cars--Auto Connector

【 Abstract 】 Automotive connectors are divided into high-voltage connectors and low-voltage connectors according to the different operating voltages. This paper summarizes the main differences of automotive high and low voltage connectors from the aspects of appearance, structure, withstand voltage, protection requirements, EMC compatibility and flame retardant grade.

Automotive connectors are divided into low-voltage connectors and high-voltage connectors according to the voltage at work. Among them, the working voltage of the low-voltage connector is mainly 12V, 24V or 48V. The working voltage of the high voltage connector refers to 60~800V, or even higher. Compared with low-voltage connectors, the difference is mainly reflected in appearance, structure, withstand voltage, protection requirements, EMC compatibility, flame retardant level and so on.

01 External View

The appearance difference between high-voltage connectors and low-voltage connectors is mainly color and volume. The low voltage connector is mainly black, and the high voltage connector is orange. Because the high-voltage connector carries high voltage and high current, the high-voltage connector is usually larger than the low-voltage connector.

02 Structure

The high-voltage connector structure is more sophisticated and complex; Compared with the low voltage connector, the internal and external shielding ring and high voltage interlock are mainly added. The structural composition of the low-voltage connector is shown in Figure 1, which is generally composed of tie rod, sealing ring, shell, TPA and other structures. The structural composition of the high-voltage connector is shown in Figure 2, which is generally composed of terminals, insulators, plastic shells, shielding rings, seals, caps, etc. Compared with low-voltage connectors, high-voltage connectors have an internal and external shielding ring. After the high voltage connector is assembled, the shielding ring will contact the shielding layer on the connector housing, and the shielding layer of the high voltage wire will eventually be placed on the iron, so as to achieve 360° shielding protection of the high voltage wire.

In addition, most high voltage connectors will also include high voltage interlock terminals, as shown in Figure 3. High voltage interlock loop connects all high voltage systems for monitoring, which is a safe design method for managing high voltage circuits with low voltage signals. At present, the high voltage connector design usually considers the high voltage interlock terminal integrated on the high voltage connector.

03 Withstand Electric Pressure

The pressure level of the connector is mainly determined by the insulation material, creepage distance, air humidity, etc. The commonly used connector materials are PBT, PA66, PA6T, PA9T and so on. Of course, the properties of different materials are different, and the price is different. According to the USCAR-37 standard, the rated voltage of the connector can be divided into 20~100V, 110~300V, 300~600V several grades.

1) Low-voltage connectors are mainly used in ECU, sensors and other positions, suitable for voltage less than 30VAC/60VDC environment.

2) High-voltage connectors are mainly used to connect high-voltage devices such as battery packs, PDUs, motors, air conditioning compressors, and heaters. At present, the rated voltage of high-voltage connectors is about 1000VDC. In order to solve the problem of the driving range of new energy vehicles, major Oems have successively launched 800V or even 1000V high-voltage architectures. The pressure level of high-voltage connectors is limited by the space environment and materials, and the future 800V or even 1000V high-voltage architecture puts higher requirements on high-voltage connector materials.

04 Guard to Ask

According to the sealing requirements, the connector can be divided into sealed connectors and non-sealed connectors. According to the different parts of the use of low-voltage connectors, the sealing requirements are also different, as shown in Table 1, can be roughly divided into S1, S2, S3 these 3 grades. Wet zone connectors generally have sealing requirements, dry zone connectors do not have sealing requirements. Only the S3 low-voltage connector has reached the IP6K9K seal grade. The sealing grade of the high voltage connector should meet IP6K9K, and also meet IP67 or even IP68. The protection level of the high voltage connector does not meet IPXXB when assembled, but meets IPXXD after assembly. IPXXB is the anti-contact protection level, and IPXXD is the probe entry detection level.

05 EMC Double Capacity

Low-voltage connectors are mainly used in voltage environments below 30VAC (60VDC), where electromagnetic interference is limited, and the wiring harness is usually shielded from electromagnetic interference by twisting or wrapping aluminum foil outside. High-voltage connectors are mainly used to connect wires and high-voltage equipment, through high-voltage wires and high-voltage equipment, the current of up to several hundred amps, the electromagnetic interference generated by it cannot be ignored, and 360° shielding must be considered. At present, high-voltage wires generally have a shielding layer, which is usually composed of braided wire and aluminum foil.

Accordingly, the high-voltage connector is also designed with an integrated shielding layer, as shown in Figure 4. The shielding layer of the connector is communicated through the shielding ring and the shielding layer of the wire to achieve 360° shielding.

06 Higher Flame Retardant Rating

The flame retardant grade of the low voltage connector has different requirements according to different parts of use. The flame retardant grade of the high voltage connector requires the highest flame retardant grade V0. The future development direction of low-voltage connectors is high-speed data transmission, lightweight, miniaturization, and integration. Compared with low-voltage connectors, high-voltage connectors in addition to meeting the basic requirements of traditional automotive connectors such as high plug and plug times and anti-vibration, in high voltage and high current environments, the requirements for heat dissipation, high-voltage protection, anti-electromagnetic interference and other aspects are more stringent, and the requirements for materials are also higher.