high voltage connector

The development of new energy high-voltage connectors

1. Electric Vehicle high-voltage connector classification

With the development of electric vehicles today, more and more electric vehicles into our lives. Whether it's an add-on electric vehicle, hybrid electric vehicle, fuel cell electric vehicle, hydrogen engine vehicle, pure electric vehicle, or other electric vehicles, etc., all require a large number of connectors. Unlike traditional fuel vehicles, electric vehicles tend to have higher voltage and current platforms, so they often have many high-voltage connectors on them.

Purely from the perspective of the connector itself, the connector has many types of classification: for example, the shape of the points have round, rectangular, etc. From the frequency, there are also high-frequency, and low-frequency, etc., and different industries will vary. This article is only for electric vehicle high-voltage connectors.

New energy vehicle high-voltage connectors New energy vehicle high-voltage connectors
High Voltage Connector

2. Fixed and plug-in type

We can often see a variety of high-voltage connectors on the vehicle, which are divided into two categories of connections according to the different ways of connecting the harness: one is a fixed bolt connection, and one is a plug-in connection.

Bolt connection is a connection we often see on the whole vehicle; the benefit of this method is its connection reliability. The bolt's mechanical force can withstand the effects of automotive-grade vibration, and its cost is relatively low. Of course, bolted connections require a certain amount of space to operate and install.

It is impossible to leave too much installation space for the increasingly platformed and reasonable space in the car. It is also not suitable from the perspective of batch work and after-sales maintenance.

And the more bolts there are, the more risk of human error, so it also has limitations. We often see similar products in the early Japanese and American hybrid models. Of course, we can still see many similar events in some passenger cars, three-phase motor lines, and in some commercial vehicles, battery power input and output lines.

This type of connection generally requires external boxes to achieve other functional requirements such as protection, so whether to use this approach needs to be arranged from the perspective of the entire vehicle power line design combined with after-sales requirements.

HVIL Connector HVIL Connector
HVIL Connector

In contrast, the plug-in connector provides a secure electrical connection to the harness by coupling two terminal housings. Since the plug-in connection can be directly inserted and closed manually, it is possible to reduce the use of space, especially in small operating spaces.

The plug-in connection has also transitioned from direct contact between the male and female ends of the cable in the early days to a middle contact with a flexible conductor material as the cross-sectional area of the cable increases and the current increases; the middle contact with a flexible conductor is more suitable for higher current connections, and its better conductive material and better flexible design structure also help to reduce the contact resistance, thus making the connection more reliable for high currents.

Contact method Contact method
Contact method

We can call the middle elastic conductor for contact; there are many kinds of contact methods in the industry, such as the more familiar spring, crown spring, leaf spring, wire spring, claw spring, etc.; of course, there are also spring type, MC strap type ODU wire spring type, etc.

Contacts Contacts
Contacts

New energy high-voltage connector structure and standards

1. High-voltage connector composition

Consists of: housing (male, female), terminals (male and female terminals), shielding cover, sealing (tail, half-end, line end, contact), tail protection cover, high-voltage interlocking system, CPA system, and other structural components.

High-voltage connector composition High-voltage connector composition

2. Standards of high-voltage connectors

High-voltage connectors are currently based on industry standards; in terms of standards, there are safety, performance, and other requirements standards and test standards. Currently, the most mainstream design of the connector manufacturers will refer to the four major European OEMs: Audi, BMW, Daimler, and Porsche, jointly developed the industry standard LV series of standards; and in North America, is mainly from SAEuscar-related standards.

USCAR itself does not draft standards, we often use uscar2, 37, and other related standards are mainly from Chrysler, Ford, GM EWCAP, a joint harness connection organization of the three major U.S. OEMs, was established in '94 and '08, to meet the requirements of the growing number of HEVs, the organization updated SAE-USCAR 2, raising the voltage level from the original 20V to the 600V we now see.

VW BMW Daimler VW BMW Daimler
VW BMW Daimler

For Europe is basically also developed jointly by the European Troika (VW BMW Daimler) OEMs, as the big brother of Germany in the development and promotion of its standards also played a very important role.

Of course, VW in the relevant industry standards inside the interests of the embodiment has also been demonstrated, for the AK working group, and even refined the installation interface size and other requirements. This is also basically in line with the consistent style of the European and American OEMs. TE Amphenol Kostal Molex Delphi and others have also joined these standards.

industry standards industry standards

Electric vehicle high-voltage connector shielding, temperature rise, protection, design material design

1. Shielding of high-voltage connectors

For high-voltage systems, shielding should take priority over the need for system-level consideration of the rationality of the arrangement, such as system-level wiring needs to pay attention to the separation of high and low voltage, alignment specifications, interference sources to be away from the signal source and so on.

High voltage connector High voltage connector

Also pay attention to the distance between the power source and the output of the high-voltage harness, such as the motor and motor controller on the whole vehicle. If you lay out far apart, then it will form the risk of common mode currents passing interference through the cable, etc.

Next is the requirements for high-voltage cables and high-voltage connectors, high-voltage harness itself industry standards require coverage of the shielding rate of 85% can be; for the connector itself to have a 360 ° shielding layer, and effective cable shield connection, the shield covers the entire length of the connection to ensure adequate shielding function, and minimize the resistance between the shielding interface. In the product life cycle, the shielding connection contact resistance is <10mΩ, and now the common value is <5mΩ.

coverage of the shielding coverage of the shielding
Schematic drawing of high-voltage wiring harness

For the connector shield structure, the current plastic-level shielding design is mostly used in the shield cover structural design. Metal connectors are passed through its own metal body, shield cover material is generally used 0.2mm ~ 0.5mm thick stainless steel and white copper for the material, 0.2 \ 0.3 mostly, basically also stamping molding, usually the end of the line to the end of the board to form an effective and 360° shielding carrier; for the connector, is generally to ensure a reliable connection between the three points of shielding 360°, the Wire end, contact end, and board end; (such as the three red dot locations on the right).

The Connector Shield Structure

For the connection between the cable to the connector shield: the majority of the current use is through the metal ring crimp cable shield, and then the metal ring and shield for a flexible 360 ° multi-point connection.

Of course, there are some OD smaller cables also have direct and metal shield metal structures with direct elastic contact. It has been found that this area is connected by spring touch finger type, which can ensure the effective contact point under complex working conditions, thus ensuring the stability of the shielding connection.

CPA structure function (push snap type) CPA structure function (push snap type)

For the shielding contact between the socket and the equipment unit: the connector basically uses multiple elastic contacts in the form of contact with the equipment end shell to achieve multi-point effective contact.

But this place for the host factory or battery manufacturers, there are 2 points to consider, the first device must need reliable grounding, if not, your connector shielding at this point must be reliably grounded; secondly, if your device surface for surface treatment, how to ensure that the connector shield can also be effective and equipment end contact this needs to be considered.

We found that this point of the problem many manufacturers either directly ignored, or directly on the surface of the device to leave the installation part without surface treatment, which is not a particularly good way. Destruction of the surface treatment of equipment, salt spray corrosion, and the need to reconsider, direct contact, contact resistance, and shielding resistance is increased, it is difficult to effectively continuous shielding; this place we can consider the installation of bolts, or internal shielding connection, etc. to consider the issue of this point.

2. Creepage distance and electrical clearance of high-voltage connectors

In order to minimize the risk of failure in high-voltage equipment, it is necessary, and given sufficient safety range, the conductors carrying high voltage must maintain a certain minimum distance, these distances are called gaps and leakage. Depending on the application in practice there are defined requirements in the IEC 60664-1 safety regulations.

1. Electrical clearance is the shortest distance in space of a live conductor

2. Creepage distance is the shortest distance along the insulating surface of an energized conductor

defined requirement defined requirement

To determine the electrical clearance (Clearance), we need to combine the following table from IEC 60664-1, according to the following four steps.

1. Determining the peak and effective values of the operating voltage.

2. Determining the supply voltage of the equipment and the category of the supply facility, determine the size of the transient overvoltage entering the equipment according to the overvoltage category.

3. Determining the contamination level of the equipment (generally contamination level 2 for equipment).

4. Determine the type of insulation of the electrical gap span (functional insulation, basic insulation, additional insulation, reinforced insulation).

IEC60664-1-table_1 IEC60664-1-table_1

If we want to calculate the creepage distance (creepage), we need to consider the following four points.

1. Determine the effective value of the working voltage or DC value; (if the value of the working voltage is between two voltage ranges, the creepage distance needs to be calculated using the internal difference method.)

2. Determine the material group (according to the leakage start index, it is divided into Ⅰ group material, Ⅱ group material, Ⅲa group material, and Ⅲb group material. Note: If you do not know the material group, assume that the material is Ⅲb group).

3. Determine the pollution level; (pollution level has four levels, general equipment for pollution level 2)

4. Determine the type of insulation (functional insulation, basic insulation, additional insulation, reinforced insulation).

Which is mainly based on CTI material category and pollution level combined with voltage value, we can find out the corresponding Creepage size according to IEC60664-1.

In practice, we can set the size flexibly according to the standard value combined with actual experience when designing, not all based on the standard.

3. High-voltage connector's temperature rise

First of all, for the temperature rise of high-voltage connectors, we must first know how to determine it and based on what standards, generally with reference to the requirements of IEC60512.

the requirements of IEC60512 the requirements of IEC60512
Derating curve derived from the basic curve
High-voltage connectors temperature rise High-voltage connectors temperature rise

For the temperature rise of high-voltage connectors, with the development of technology, the high-power trend will become increasingly popular. For high-voltage connectors, how not by increasing the specifications of the cable, withstand greater loads is the subject of research.

Usually, our requirements for the connector temperature rise is required less than 50K, For the temperature rise of high-voltage connectors, we need to examine the temperature of three areas: the terminal connection area, the terminal contact area (connector itself), and the terminal crimping area.

Terminal connection area: We for the end of the device and the end of the board connected to the connector will usually be connected to the end of the device in the form of a copper row through the bolt or lock bolt form. Of course, there are also directly connected through the bolt and nut directly, no matter which, this place we need to ensure a lower temperature rise will have to consider effective connection, especially in complex vehicle conditions, to reduce the nut loosening and other undesirable problems.

Because these problems will lead to a rise in contact resistance, thus increasing the heat of this area, a serious instantaneous current will burn this area; we can provide the stability of this connection by strictly following the locking torque, loosening the nut, gluing, and other forms.

the terminal connection area, the terminal contact area , the terminal crimping area the terminal connection area, the terminal contact area , the terminal crimping area

Terminal contact area: The heating of this area is an assessment of the current-carrying capacity of the contact pair; the more effective contact points of the electrical connection, the larger the contact area, the lower the contact resistance, and the contact resistance is an important electrical performance indicator to consider the reliability of the contact.

For the contact pair, we need to consider the design from the material level, electrical performance level, mechanical plugging, micro-vibration impact, and other comprehensive factors in the design; we can use some additional tools in this place to build a microscopic mathematical model to analyze the current for the change in the contact pair, as well as temperature changes in the walk; the study of the contact pair requires a deep knowledge of electrical contact theory, but also requires a large number of tests and analysis.

Terminal crimping area: The problem of high temperature caused by poor crimping is also very common. For connector manufacturers in the design of the connector terminals, you need to systematically consider the different specifications of the crimp cup crimp and crimp size; the final harness manufacturers should be strictly based on the design of the connector crimp cup crimp method and size specifications for crimping.

For the technical requirements and management of crimping, we determine whether it is good or bad pressure has a very important indicator, which is to see its crimp duty cycle. Empirical value, the duty cycle of≥ 85%, is relatively good; the duty cycle is to determine whether your conductor is fully utilized inside the crimp cup; in addition to the duty cycle, of course, we have to look at its pull-off force, the value of different wire gauge in many of the standards are corresponding. Of course, for crimping, we must also examine its crimp resistance, which is also a very important indicator; the mass system standards also have provisions.

4. Protection of high-voltage connectors

High-voltage connector protection is currently the most problematic connector performance point on the market. In terms of protection, the priority given to: IP2X/IP67/IP68/IP6K9K. Currently, the domestic high-voltage connectors have generally required to meet the technical requirements of IP68.

Protection of high-voltage connectors Protection of high-voltage connectors

Electric vehicle high-voltage connector development trend

From the perspective of the whole vehicle can see the vehicle is increasingly fast platform, modular. For high-voltage connectors, from the perspective of a single vehicle will indeed be reduced by many points, but from the perspective of the overall market, this is still a huge market.

Connector Type 2015 2020 5-Year
CAGR
High Voltage-High Current Connectors $21 $50 18.90%
Harness Connectors $14 $32 18.80%
PCB Connectors $4 $9 19.00%
RF Connectors $0 $1 18.90%
Low Voltage Lugs and Terminals $0 $0 18.20%
Fiber Optic Connectors $0 $0 31.50%
Total $39 $93 18.90%

2015 and 2020F European Full Electric Vehicle Connector Market by Connector Type with Five-Year CAGR

Connector Type 2015 2020 5-Year
CAGR
High Voltage-High Current Connectors $224 $309 6.60%
Harness Connectors $207 $277 6.00%
PCB Connectors $52 $70 6.30%
RF Connectors $8 $12 7.00%
Low Voltage Lugs and Terminals $1 $1 2.90%
Fiber Optic Connectors $1 $2 24.30%
Total $493 $672 6.40%

2015 and 2020F Japanese's Electric Vehicle Connector Market by Connector Type with Five-Year CAGR

Connector Type 2015 2020 5-Year
CAGR
High Voltage-High Current Connectors $38 $152 31.90%
Harness Connectors $48 $184 30.60%
PCB Connectors $13 $50 30.90%
RF Connectors $2 $7 32.20%
Low Voltage Lugs and Terminals $0 $1 26.50%
Fiber Optic Connectors $0 $2 45.30%
Total $102 $395 31.20%

2015 and 2020F European Hybrid Electric Vehicle Connector Market by Connector Type with Five-Year CAGR

Connector Type 2015 2020 5-Year
CAGR
High Voltage-High Current Connectors $213 $287 6.20%
Harness Connectors $202 $268 5.80%
PCB Connectors $51 $68 6.00%
RF Connectors $8 $11 6.80%
Low Voltage Lugs and Terminals $1 $1 2.60%
Fiber Optic Connectors $1 $2 24.00%
Total $475 $637 6.00%

2015 and 2020F Japanese Hybrid Electric Vehicle Connector Market by Connector Type with Five-Year CAGR

1. Higher current

In the short term, because the voltage platform of the whole vehicle can't be raised quickly, with the requirements such as increased range, the current is certain to increase, which requires the power plug-in to be able to withstand higher current. Most of the current industry standards are based on 8mm terminals, which generally can only withstand the rated 250A or so.

At present, each family is also gradually developing a new generation of high-current power plug-ins, such as Amphenol TPI's 450A current; how to increase the current, and reduce the temperature rise, thereby maximizing the use of cable conductivity. Reducing the number of cable squares is a key consideration for all companies, but we can also try to consider the cooling system and power plug-in circuit to achieve the goal of high current, lower temperature rise, and lighter weight.

2. Data analysis, environmental simulation

The entire electric vehicle has nearly 20 years of recent development, for the vehicle, has accumulated more data, the data will be very effective in helping to build a complete environmental model, which can be effective for simulation analysis and avoidance of the life of the vehicle components, safety hazards, failure mechanisms, etc.

Connector manufacturers have also accumulated a large amount of practical application experience and database, how to use these actual data, mathematical simulation modeling so as to avoid the actual problems from the design side more reasonable, how to use these figures to build environmental models, can bring the design into a better simulation of its service life.

3. The future of connectors

As cars become increasingly intelligent, for the connector in the future of smart cars, will never just as an electrical connection point for transmission, this and traditional cars will be very fundamentally different. The future of the connector is likely to become modular, its function will be different with different car parts application scenarios, the function will be different.

At the same time the emergence of intelligent driving will make the connection for the stability of the transmission becomes mandatory, for the reliability of electrical performance, as well as other performance will be mentioned a higher level of requirements.