To understand new energy, these 5 high-voltage wiring harnesses must be understood!
In new energy vehicles, whether they are hybrid or pure electric models, the importance of the high-voltage system as one of the core components is self-evident. The high-voltage wiring harness, as a medium for interconnecting various components in the high-voltage system, also plays an indispensable role.
Due to the impact of the working environment and safety of high-voltage systems, high-voltage wiring harnesses must improve their own capabilities, such as the following performance requirements.
Voltage resistance performance:
Passenger cars generally use a rated voltage of 600VAC/900VDC, while commercial vehicles generally use a rated voltage of 1000VAC/1500VDC.
Current resistance performance:
According to the current of high-voltage system components, it is commonly used at 250A, and some high-power motors can be used up to 400A.
Temperature resistance performance:
The high temperature resistance level is divided into 125 ℃, 150 ℃, and 200 ℃, and high temperature resistant 150 ℃ wires are commonly selected; Low temperature conventional selection: low temperature resistant -40 ℃ wire.
Shielding performance:
Shielding high-voltage lines can reduce the impact of electromagnetic interference (EMI) and radio interference (RFI) on the entire vehicle system. The entire high-voltage wiring harness circuit is shielded and connected. The shielding layer of the high-voltage wiring harness for the motor, controller, and battery interfaces is connected to the battery motor controller housing through a plug-in and pressure equalization structure, and then connected to the vehicle body grounding.
What else do we need to know about high-voltage wiring harnesses besides the basic performance mentioned above?
Firstly, we need to know that in new energy vehicles (such as pure electric vehicles), high-voltage wiring harnesses can be divided into five main parts
1. High voltage cable for power battery: the wiring harness that connects the power battery to the high-voltage box
2. Motor controller cable: the wiring harness connecting the high-voltage box to the motor controller
3. Fast charging wire harness: the wire harness connecting the fast charging port to the high-voltage box
4. Slow charging harness: the harness connecting the slow charging port to the car charger
5. High voltage accessory harness (high voltage harness assembly): refers to the harness that connects the high voltage box to the DC/DC, car charger, air conditioning compressor, and air conditioning PTC.
In the entire high-voltage system wiring harness, in addition to the high-voltage wiring harness, there is another type of wiring harness called the safety wire.
This harness is a 12V circular wire that passes through various high-voltage components. If the safety line at a certain point is interrupted, the data bus diagnostic interface unit J533 (i.e. gateway) will obtain information from the relevant control unit and display a prompt message to the driver through the instrument unit J285.
It should be noted that in the event of a safety line interruption, as long as the ignition switch is not turned off, although the vehicle can still continue to drive, the drive system cannot be activated again at this time.
The high-voltage battery switch box plays an important role as a link between the power battery and other high-voltage components.
It is installed on the high-voltage battery and communicates with the battery regulation control unit J840 and the battery module control unit through a sub CAN bus. The DC charging contactor will only engage when charging the high-voltage battery through a DC charging station.
Transformer A19 is installed at the front right of the vehicle and uses coolant circulation for cooling. Responsible for converting the 396V DC power from the high-voltage battery into 12V DC power for the vehicle's power grid.
The transmission of current is achieved through coil induction, so there is no wire connection between the high-voltage system and the 12V vehicle power grid.
The high-voltage battery charging device is located above the front drive motor and connected to the vehicle body through an equipotential wire.
The high-voltage heater is installed at the front of the vehicle and is supplied with high-voltage electricity through a fuse inside the high-voltage battery switch box. Heating the coolant to provide warm air for the vehicle or to heat the high-voltage battery (in low-temperature environments), also connected to the vehicle body through an equipotential wire.
What are the hazards of alternating current compared to direct current?
AC voltage causes AC current in the human body and induces muscle and heart tremors. The lower the frequency, the more dangerous it is. The consequence may be ventricular fibrillation, and without emergency measures, it may lead to death.
For direct current, electrolytic solvents can corrode fabrics. Therefore, substances that may cause poisoning are produced. A few days after the accident, the so-called direct current poisoning will only manifest, and if left untreated, it can lead to death.
02 Dangerous values of current and voltage
AC voltage above 25 V and DC voltage above 60 V can become dangerous.
When the current flowing through the human body exceeds about 5 mA, it is called 'charged'. People may feel numb, but they can still get rid of electrical conductors.
When the current passing through the human body exceeds about 10 mA, which triggers the "conductor release threshold" for body spasms, the power source cannot be disconnected.
When an AC current of 30-50 mA is applied for a long time, respiratory arrest and ventricular fibrillation occur.
When the current of the human body reaches about 80 mA, it is called the "critical value of death".
The electric air conditioning compressor is installed at the front of the vehicle and is supplied with high voltage electricity through a fuse box inside the high voltage battery switch box. When the parking air conditioning is working, the high-voltage system is activated and the high-voltage components are energized.
