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What’s the HVIL on new energy Vehicle?

High Voltage Inter-lock (HVIL for short), a safe design method for monitoring the integrity of high-voltage circuits with low-voltage signals. Theoretically, the low-voltage monitoring circuit is connected first and then disconnected than the high voltage, and the necessary advance is maintained in the middle. The length of time can be determined according to the specific situation of the project, such as 150ms, which is roughly in this order. Specific implementation forms of high-voltage interlocking may have different designs for different projects. The monitoring target is an electrical interface element such as a high-voltage connector that requires manual operation to achieve circuit on or off.

 In the high-voltage circuit of electric vehicles, the electrical components that require HVIL function are mainly high-voltage connectors and manual maintenance switches (MSD).

 High-voltage Inter Lock Principle

 There are two aspects of the high-voltage interlock design that need to be considered. One is how the low-voltage system can comprehensively detect the connection status of each connection position of the entire high-voltage system. The other problem is how to achieve the information transmission action of the low-voltage detection circuit. Open circuit action. Therefore, the high-voltage interlocking principle needs to proceed from these two aspects, considering the overall circuit design principle and the connector design principle.

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Why do new energy vehicles require high-voltage interlocking?

Causes of high-voltage interlocking

 From the perspective of system functional safety, every possible risk needs to be configured with corresponding security technology means to monitor it to reduce the probability of risk. From this level, high-voltage interlock is used as a safety measure for the safety of high-voltage systems in electric vehicles and is used in circuit design.

new energy vehicles require high-voltage interlocking

 One of the risk points of the high-voltage system of electric vehicles is the sudden power failure and the car loses power. There are several reasons that can cause a car to lose power, one of which is the automatic release of the high-voltage circuit. The high-voltage interlock can detect such signs and provide alarm information to the vehicle controller before the high-voltage power failure, and reserve time for the vehicle system to take countermeasures. Another risk point of electric vehicles is human error operation. During the work of the system, the high-voltage connection point is manually disconnected. If there is no high-voltage interlocking design, at the moment of disconnection, the entire loop voltage is applied across the breakpoint, which is very dangerous for devices such as high-voltage connectors that do not have breaking capability. The voltage breakdown air draws an arc between the two devices. Although the time is short, it can be very high, which may cause damage to people and equipment around the breakpoint.

 Purpose of high voltage interlock

 Regarding the specific purpose of high-voltage interlocking, there are several different claims. Some people think that the high-voltage interlock mainly plays a role before the vehicle is powered on. If the circuit is detected to be incomplete, the system cannot be powered on to avoid accidents caused by problems such as virtual connections. Others believe that the high-voltage interlock is mainly caused by collision failure It plays a role in the process of electricity. The collision signal triggers the high-voltage interlock signal to power off the system. However, in a more critical situation after a collision, the fewer steps to perform a power outage, the better, and the collision signal is directly passed to the VCU, which is logically more reasonable.

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How to select high voltage connector？

In the field of new energy vehicle industry, high-voltage connectors are extremely important components, and are used in vehicle and charging facilities.

High Voltage Connector

The function of the connector is very simple: between the blocked or isolated circuits in the circuit, a communication bridge is established, so that the current flows and the circuit achieves the predetermined function.

The main application scenarios of the high-voltage connector on the vehicle are: DC, plumbing PTC charger, wind heating PTC, DC charging port, power motor, high-voltage wiring harness, maintenance switch, inverter, power battery, high-voltage box, electric air conditioner, AC charging Mouth, etc.

Electric vehicles have very strict requirements for connector performance. High mating times, current carrying capacity, CTI value, flame retardant performance and vibration resistance are the factors to be considered in product development of enterprises. At present, the power requirements of electric drive units for new energy vehicles are increasing. The working current and voltage put forward higher requirements. The traditional connection voltage is about 14V, while the voltage of the high-voltage connector of electric vehicles reaches 400-600V.

At the same time, high-pressure connector seals are generally required to reach at least IP67. In some special occasions of the automobile, IP6K9K is even required to ensure that the requirements are met even during high-pressure flushing.

Because new energy vehicles use a large number of power electronic devices, electromagnetic fields generated by high voltage and large currents will cause electromagnetic interference to other communication equipment. The entire vehicle and parts must have the ability to resist interference and radiation.

When designing a high-voltage electrical connection system, the connector is required to have a 360 ° shielding layer and be effectively connected to the cable shielding layer. The shielding layer covers the entire connector length to ensure sufficient shielding function and minimize the resistance between shielding interfaces. During the product life cycle, the contact resistance of the shield connection is <10mΩ.

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Automotive wiring harness waterproof rating

Harness waterproofing is a necessary content in harness work. If the harness waterproofing fails, it will easily cause abnormal working of various electrical systems, affect the comfort of the vehicle, and even cause a great safety risk. After the design is completed, waterproof experiments should be performed to check the reliability of the waterproof design. Below I will briefly introduce the definition and test method of waterproof grade of automotive wiring harness.

Our common expression is IPXX or something. IP and the following two digits have some meaning. The IP (INGRESS PROTECTION) protection level system is drafted by IEC (INTERNATIONAL ELECTROTECHNICALCOMMISSION), which classifies electrical appliances according to their characteristics of dust and moisture resistance. The IP protection level is composed of two numbers. The first number indicates the level of the appliance that is dust-proof and protected against foreign objects. In order to avoid electric shock), the second number indicates the degree of tightness of the appliance against moisture and water. The higher the number, the higher the protection level.

The protection level is mostly expressed by IP followed by two numbers, which are used to clarify the protection level. The first digit indicates the extent to which the equipment is resistant to dust, or the extent to which people are protected from harm in a sealed environment. Represents the level of preventing solid foreign matter from entering, the highest level is 6; The second digit indicates how waterproof the device is. Represents a level to prevent water ingress. The highest level is 8. Such as motor protection class IP65. Protection against electrical equipment and foreign objects (first digit) Protection against electrical equipment (second digit)IP dust-proof rating (the first X indicates)0: No protection 1: Prevent large solids from entering 2: Prevents intrusion of medium-sized solids 3: Prevent small solids from entering 4: Prevent solid objects larger than 1mm from entering 5: Prevent the accumulation of harmful dust 6: completely prevent dust from entering Because the general wiring harness has high requirements for dust resistance, we default it to 6, which is why we often use IP6X to indicate the waterproof rating of the wiring harness on the supplier’s report or drawing.IP waterproof rating rangeThe waterproof test includes the second characteristic number from 1 to 8, that is, the protection level code is IPX1 to IPX8. No protection No special protection 1 Prevent dripping water from entering 2 Prevents dripping water when inclined at 15 degrees Prevents dripping water when electrical equipment is inclined at 15 degrees 3 Prevent sprayed water from entering Rainwater or sprayed water with a vertical angle of entry less than 50 degrees 4 Prevent splashing water from entering Water splashing from all directions 5 Prevent the intrusion of large waves of water 6 Prevent the intrusion of large waves of water. Electrical equipment can intrude into the water to ensure the normal operation of the equipment under certain conditions of time or water pressure. 7 Prevent the intrusion of water ingress The electrical equipment can be sunk indefinitely under certain water pressure conditions to ensure normal operation 8 Preventing the effects of sinking