Design and verification of high voltage connectors

High voltage connector is also known as high voltage connector, is a kind of automotive connector, generally refers to the working voltage above 60V, mainly responsible for the transmission of large current connector.

The high-voltage connector ensures the safety and stability of the connector by maintaining the stable contact of the conductive part, and the use of insulating materials and sealing structures, so as to achieve the transmission of high-voltage power or signals.

There are many brands of high voltage connectors, and the international well-known brands mainly include Tyco, Amphenol, Molex, Ambofu and so on. China also has some excellent high-voltage connector brands, such as AVIC Optoelectronics, Rukeda, Yonggui Electric and so on.

At present, the high voltage connector mainly has three standard systems, respectively, LV standard plug-in, USCAR standard plug-in, and Japanese standard plug-in, the three plug-ins are currently the largest liquidity in the domestic market with LV, the most perfect process standards.

GB/T 20994-2007, specifies the safety requirements and test methods for high voltage connectors.

QC/T 1039-2016, specifies the technical requirements and test methods for automotive high-voltage connectors.

1 Basic components of high voltage connectors

The high voltage connector is mainly composed of four basic structures, which are contactors, insulators, plastic-case and accessories.

(1) Contact parts: the core parts to complete the electrical connection, namely male and female terminals, reed, etc.;

(2) Insulator: support the contacts to ensure the insulation between the contacts, that is, the inner plastic shell;

(3) Plastic shell: the shell of the connector to ensure the alignment and protection of the entire connector, that is, the outer plastic shell;

(4) Accessories: including structural accessories and installation accessories, that is, positioning pins, guiding pins, connecting rings, sealing rings, rotating bars, locking structures, etc.

2 Design requirements for high voltage connectors

High voltage system requirements for high voltage connectors include but are not limited to: high voltage, high current performance; Need to be able to achieve a high level of protection under various working conditions (such as high temperature, vibration, impact, dust and waterproof, etc.); Have installability; Good electromagnetic shielding performance; The cost should be as low as possible and durable.

The design requirements of high voltage connectors mainly include the following aspects:

Electrical performance requirements: The high voltage connector must meet the electrical performance requirements such as insulation resistance, dielectric loss Angle tangent value, discharge current, and voltage resistance test at rated voltage. In addition, it is also necessary to consider the rated current, contact resistance, temperature rise and other parameters.

Environmental adaptability requirements: High-voltage connectors need to be able to adapt to a variety of harsh working environments, such as high temperature, low temperature, humidity, vibration, etc. The impact of these factors on connector performance needs to be considered during design, and corresponding measures should be taken to optimize.

Mechanical strength requirements: High voltage connectors need to withstand a certain amount of mechanical stress, so they need to have sufficient mechanical strength. The design requires detailed analysis and calculation of the structure of the connector to ensure that it can withstand various stresses.

Sealing performance requirements: High voltage connectors need to have excellent sealing performance to prevent impurities such as water and dust from entering the interior of the connector, affecting its electrical performance and safety. The design requires the use of reliable sealing materials and sealing structure, and the appearance of the connector is strictly checked.

Reliability requirements: High voltage connectors need to have high reliability to ensure that they can maintain stable performance during long-term use. The design requires the use of high-quality raw materials and advanced process technology, and adequate testing and verification.

Safety performance requirements: High voltage connectors need to have sufficient safety performance to prevent the occurrence of dangerous situations such as electric shock and short circuit. The design needs to adopt safety protection measures, such as setting grounding protection, overcurrent protection, etc., and strictly control the temperature rise of the connector.

Technical requirements of SAE J1742 High Voltage connector:

Operating temperature: -40° C ~125 ° C

Voltage resistance: meet the creepage distance and electrical gap requirements, meet the rated voltage requirements of 750V

Insulation resistance: Under normal conditions, ≥500MQ

In hot and humid conditions, ≥5MQ

Contact resistance: ≤0.2MΩ

Insertion and removal times: ≥500 times

Seal protection level: In addition to copper joints, when the connector is engaged, no matter where it is installed, the connector protection level should not be less than IP68

Protection level against electric shock: IPXXD

High voltage interlock: Depending on product type and customer needs

EMC: High-voltage connectors with shielding requirements are 360-degree shielding, EMC must meet the national standard GB/T37133, and the shielding efficiency of the wiring harness assembly is ≥75dB.

Anti-corrosion requirements: To prevent corrosion of copper joints, the surface of copper joints needs to be tinned. And through LV214 "Automotive Connector test specification" related salt spray test requirements, after the test conductivity is 100%

Service life: Plug and remove life, all connectors meet 50 plug and remove requirements.

Connectors must have a 15-year service life.

Connector in use to meet the lifetime maintenance free use requirements.

Color design: The plastic high voltage connector design is orange, the same color as the high voltage wire.

Meet the working voltage of the whole vehicle and the power of the controlled electrical parts

3 Experimental test of high voltage connectors

High voltage connectors require a series of experimental tests to ensure their performance and safety. Here are some common experimental tests:

Mechanical strength test: including durability test, vibration test, impact test, etc., to check the mechanical strength and reliability of the connector.

The high voltage connector is installed on the high voltage equipment, and will suffer various vibrations and shocks in the actual use of the vehicle. This vibration and shock can cause terminal contact surface wear, electrical connection discontinuity, and mechanical component failure in high voltage connector systems.

The test piece needs to be connected to a complete male and female connector (high voltage wire harness end connector and high voltage equipment end connector), and ensure that its connection resistance meets the requirements.

Electrical performance test: including rated voltage, rated current, contact resistance, temperature rise and other aspects of the test to ensure that the connector can maintain good electrical performance under normal working conditions.

Environmental adaptability test: including temperature cycle, humidity, salt spray, mold and other environmental factors to evaluate the performance of the connector under different environmental conditions.

High temperature aging, thermal aging can change metals and plastics, and these changes can cause harm to electrical and physical properties. High temperature exposure test is used to simulate the effects of high voltage connectors exposed to high temperature for a long time.

Temperature shock, cold and thermal shock test is an extreme temperature cycle test on various materials in the connector system, through the expansion and contraction of various materials of the connector, so that the friction between the terminal and the terminal contact surface is accelerated, in order to assess the connector in storage, transportation and use may encounter sudden changes in air temperature tolerance.

Wet heat cycle, high humidity and high temperature can accelerate the terminal current and electrolytic corrosion, temperature cycle can cause wear and friction corrosion of the contact surface relative movement, leading to the deterioration of the electrical and mechanical properties of the high-voltage connector. In order to evaluate the electrical durability of a high-voltage connector system, changes in temperature and humidity need to be used as aging factors to simulate the actual use of the vehicle.

Salt spray corrosion, the purpose of salt spray corrosion test is to test the corrosion resistance of high voltage connectors.

Sealing performance test: including air tightness test, water tightness test, etc., to verify the sealing performance and dustproof and waterproof ability of the connector.

The purpose of the waterproof sealing test is to test the sealing performance of the high voltage connector. The water tightness test and high pressure spray test were carried out by using the cold and thermal impact testing machine.

Reliability testing: including life testing, failure mode and impact analysis to assess the reliability and stability of the connector.

Safety performance test: including overload protection test, short circuit protection test, electric shock protection test, etc., to ensure that the connector can safely cut off the power supply or release energy when encountering abnormal conditions.