1. Application in charging pile (machine)
used for DC charging pile, DC output side of charging station or output side of on-board charger. When the contactor is closed, it plays the role of connecting the charging pile and the car; when it is disconnected, it isolates the charging pile from the external connection and plays a role of safety protection. Figure 1 
2. Application in electric vehicles
A DC contactor is disposed between the battery system and the inverter of the electric vehicle. When the system stops running, it plays an isolation role, and when the system is running, it plays a connection role. When the vehicle is shut down or fails, the energy storage system can be safely separated from the vehicle electrical system to break the circuit. It is used as an electrical control device in other auxiliary circuits. Figure 2 
Figure 2. Application of DC contactor in electric vehicle
important technical indicators:
a) Isolate the power end and the load end after the system stops running; (Important technical index: rated insulation voltage Ui)
b) Connect the power end and the load end when the system is running; (important technical index: agreed heating current Ith)
c) Breaking the circuit in case of failure. (Important technical indicators: maximum operating voltage U)
3. Adaptive design of products
1. Environmental Adaptability Design:
different from general industrial contactor products, the use of environmental conditions for the adaptability of electric vehicle contactors more stringent requirements, must also meet the wide temperature range, high protection level, high vibration resistance and other basic conditions.
1) High and low temperature design: It is necessary to meet the temperature requirements of electric vehicles and charging piles (machines) for normal use in extreme weather. Product storage environment temperature:-55~125 ℃, normal working environment temperature is -25~40 ℃, under extreme conditions, the ambient temperature is -40~85 ℃,
2) Protection level design: to meet the normal work under harsh environmental conditions, normal use in rain and dust environment, the product completely prevents dust from entering, meets the requirements of short-term immersion, and the protection level reaches IP67.
3) Anti-vibration performance design: The product must have strong vibration resistance and impact resistance. Meet the special needs of the car used in a variety of road conditions bumpy vibration.
2. Safety and reliability design
safety and reliability is the first and most critical element to measure the DC contactor of electric vehicles, which is mainly reflected in the arc extinguishing capacity, insulation voltage and so on.
DC arc has the characteristics of no zero crossing point and the arc is difficult to extinguish after arc ignition. The product structure is designed as a double break point direct motion form. And the arc extinguishing technology of filling compressed gas in the sealed arc extinguishing cavity can achieve good arc extinguishing ability. The main principle is: after the arc is heated, high-pressure gas is formed with the filled gas. The increase of gas pressure makes the heat free drop greatly. The pressure difference between the arc gap and the arc extinguishing chamber accelerates the gas movement, intensifies the cooling effect, and the arc is quickly extinguished.
Special 4. materials and key processes
the R & D and design of any product must rely on the appropriate selection of raw materials, advanced process measures, stable parts and tooling, and perfect manufacturing processes before it can be completely transformed into products. Raw materials, manufacturing processes, and production lines are all key elements of design transformation.
1) Material property requirements for key components of electric vehicle DC contactors
| material Name | material Requirement Characteristics |
| arc extinguishing chamber material | high temperature resistance, high electrical strength, high mechanical strength, good insulation performance, stable chemical performance, corrosion resistance |
| terminal | high purity, high conductivity, easy welding, corrosion resistance, good welding performance |
| magnetic yoke | corrosion resistance, good oxidation resistance, high magnetic permeability |
| arc extinguishing medium | stable performance, good arc extinguishing ability |
| magnetic blowing permanent magnet | stable performance, not easy to oxidize, good dielectric properties, high magnetic permeability |
| welding liner of arc extinguishing chamber | small expansion coefficient, good welding performance |
| epoxy sealing material | high voltage resistance, impact resistance, aging resistance, high shear and high peel strength, high and low temperature resistance Small shrinkage, small linear expansion coefficient, high bonding strength |
| guide rail | wear resistance, flame retardant ability, high and low temperature resistance, good lubricity. |
2) Key process design and equipment support
manufacturing process as a sufficient condition to ensure reliable product quality and stable performance, must rely on certain hardware facilities to be guaranteed, tooling equipment and production lines bear the brunt.
1. Welding process and equipment:
laser welding process is the key guarantee process of product quality and reliability. The main purpose of welding is to ensure a good sealing effect, prevent the coil and contact from oxidation and pollution, and ensure the stability of its contact resistance.
The arc extinguishing chamber is sealed and welded by laser welding technology, so that the welding between the arc extinguishing cover and the magnetic yoke, and between the magnetic yoke and the sealing sleeve is not leaking.
The air tightness of the arc extinguishing chamber after welding is tested to ensure that there is no air leakage in actual use. Suction and inflate the contact system after welding and the whole machine after filling glue. After the inside of the workpiece is vacuumed, the gas is inflated according to the gas type and pressure specified by the process, and the inflation port is automatically sealed.
Essential key equipment: laser welding machine, air tightness detection device, vacuum inflation device.
2. Encapsulation process and equipment
glue pouring process is one of the key processes of epoxy glue sealing contactor. The combination degree of glue and product body and the density of colloid are the key points to be guaranteed.
In the glue filling process, the air inside the product, the bubbles inside the colloid, and the bubbles generated during the filling process will affect the penetration effect of the glue and the density of the colloid, thereby affecting the sealing performance of the product. Using the vacuum glue filling system, all the air in the glue tank is pumped out and kept in a certain vacuum state. Before filling glue, the air inside the product is pumped clean to reach a certain negative pressure, and then the product is filled with glue. Under the action of negative pressure, glue can quickly and evenly penetrate into the product, and bubbles generated by filling impact and contact between glue and the product will also be drawn away, thus ensuring uniform coverage of glue on the contact surface of the product and uniform density of colloid, and achieving good glue filling effect.
After the glue filling is completed, the product needs to be placed in a drying box for curing, and a constant and uniform temperature field, reasonable curing time and heating and cooling rate are maintained when the glue is baked. The curing internal stress and temperature internal stress reach the minimum value, which ensures good curing effect and bonding effect, so as to achieve good sealing effect.
Necessary key equipment: glue filling machine, vacuum workbench, glue drying device.
3. Testing process and equipment
reliable electrical life of the contactor is a key performance indicator, and the load failure test is the last guarantee before the product leaves the factory.
Essential key equipment: DC power supply, resistive load, intelligent control and protection device
5. product special needs selection
1. For some charging cabinets that need to complete the battery charging and discharging function requirements, the main contact non-polar DC contactor product can be selected (this design has been patented by Tianshui 213 Electric Appliance Co., Ltd.) to break through the structural design limitation of the lead wire specially for the current direction.
2. According to the limited installation space, choose a reasonable wiring mode product, as shown in the figure.
GSZ8-200 copper wiring
Wiring mode of GSZ8-200 screw
6. market product profile:
at present, the mainstream products of electric vehicle contactors are mainly divided into two categories: ceramic cavity sealing structure and epoxy glue sealing structure.
As follows: 
GSZ8 series ceramic cavity sealing structure
JSE Series Epoxy Sealing Structure
the rated current has a plurality of levels of 10A, 20A, 25A, 40A, 60A, 50A, 80A, 100A, 120A, 150A, 200A, 250A, 300A, 400A, etc. Control voltage 9 ~ 36VDC. Rated insulation voltage 1000VDC, breaking voltage 900VDC.
Conclusion:
the consistency of electric vehicle contactor products affects the reliability and stability of products, and product consistency runs through all product formation processes: design, material consistency, stability of parts and tooling, stability of assembly process, Stability of assembly tooling, etc. Broad view and about take, thick accumulation and thin hair.
Above is introduction of Ancojet Testing and Certification to DC Contactor, for reference only, some of the materials come from the electric vehicle consulting network and do not represent the views of Ancojet's testing technology and are responsible for its authenticity. If you are involved in the content of the work, copyright and other issues, please contact us within 30 days, we will delete the content in the first time!
