In the high-voltage circuit of electric vehicles, the high-voltage connector of the main electrical components in the high-voltage interlock system.
On the one hand, when the high-voltage system circuit is disconnected or the integrity is damaged, the high-voltage interlock starts the protection measures to safely disconnect the high-voltage electricity; on the other hand, it is used to confirm the integrity of the entire high-voltage system.
What is a high voltage interlock system?
High Voltage Interlock (HVIL), also called Hazardous Voltage InterlockLoop.
HVIL or High Voltage Interlock Loop is a safety feature in hybrid and all-electric vehicles that protects personnel during vehicle assembly, repair, maintenance and operation.
The HVIL system is designed to protect anyone who may come into contact with high voltage components at any stage of the EV life cycle.
Gas-powered vehicles do not require HVIL because their electrical systems operate at low voltage and pose no risk to operators and service technicians. But hybrid and electric vehicles include subsystems of batteries, wires, adapters and controllers that operate at higher power levels and therefore require additional safety features.
The HVIL acts as a circuit breaker that sends an alert or fault code to the driver if a high-voltage connection becomes loose, disconnected, or damaged during vehicle operation. HVIL also helps protect the driver and passengers of the vehicle in the event of an accident.
Among them, high-voltage interlock refers to a safe design method that monitors the integrity of high-voltage circuits with low-voltage signals. By using low-voltage signals to check all components connected to the high-voltage wiring harness on the electric vehicle, the electrical connection integrity and continuity of each high-voltage system circuit are detected.
Theoretically speaking, the low-voltage monitoring circuit is connected first and then disconnected than the high-voltage monitoring circuit, and the interval is a certain period of time (for example, 150ms). The specific high-voltage interlock realization form has different designs for different projects.
At present, it is mostly used in the form of integration on the high-voltage wire harness connector. That is, on the high-voltage harness connector, an additional set of low-voltage loops are used to detect the loop integrity of the HVIL.
Another form of high-voltage interlock connector is more complex in design. The high-voltage interlock structure is independent of the inner plastic shell or connected by a separate small connector, which is guaranteed by the sequential installation relationship of the two connectors.
The role of high voltage interlock
Function 1: Before the vehicle is powered on, if it is detected that the circuit is incomplete, the system cannot be powered on to avoid accidents caused by virtual connections and other problems;
Function 2: Prevent safety accidents caused by human misoperation. During the working process of the high-voltage system, if there is no high-voltage interlock design, when the high-voltage connection point is manually disconnected.
At the moment of disconnection, the entire loop voltage will be applied to both ends of the breakpoint, and the voltage will break through the air and draw an arc between the two devices. Although the time is short, the energy is very high, which may affect the personnel and equipment around the breakpoint. cause some damages.
Function 3: Detect the looseness of the high-voltage circuit (which will cause the high-voltage power failure, the vehicle loses power, and affect the safety of the car), and provide alarm information to the vehicle controller before the high-voltage power failure, so as to reserve time for the vehicle system to take countermeasures.
System composition
The components of a high-voltage connector with a high-voltage interlock function are: a low-voltage signal conductor, a high-voltage conductor, a housing, a monitoring circuit and a monitor.
The general implementation of the high-voltage interlock structure is as follows: a pair of low-voltage connectors and a pair of high-voltage connectors are respectively fixed on a pair of male ends and female ends that are inserted into each other.
Through the length and position difference between the interlock terminal and the main circuit (high voltage) terminal, when connecting, connect the high voltage terminal first, then connect the low voltage terminal; and when disconnecting, disconnect the low voltage terminal first, then disconnect the high voltage terminal.
Part of a complete security solution
HVIL is only one aspect of a comprehensive approach to safe electricity use in EVs. There are thousands of connection points inside a typical electric vehicle. If any of these malfunction, the result can range from a minor inconvenience to a major, life-threatening problem.
High voltage connectors throughout the vehicle also offer finger-proof, touch-safe two-step disconnect technology to ensure optimum safety during all handling operations. These measures protect consumers or service technicians who may accidentally touch the disconnect by making it impossible for anyone to access any internal parts of the metal electrical contacts.
Melt-in connectors and other innovations ensure that if current spikes reach potentially dangerous levels, the battery will be disconnected from the rest of the car and the charger, eliminating any chance of a catastrophic event.
Another way to reduce risk (even with elevated voltages) is to exceed the maximum safety specifications set by the OEM. Most specifications cover vehicles in the 600V to 750V range, but connector suppliers typically design their products for 1,000 volts.
HVIL technology is important, but it is also important for OEMs to see HVIL in the larger context of hybrid or fully electric vehicles that are built to the latest safety and performance standards across the electrical infrastructure.
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