Electric Vehicle High Voltage Interlock

       I Definition of high-voltage interlock

High-voltage interlock, also refers to the hazardous voltage interlock loop (HVIL): by using small electrical signals to check the electrical continuity of the whole high voltage product, wire, connector and cover. When the circuit is identified as abnormal, it will disconnect the high voltage in time.

II The principle of interlock

1、Schematic diagram of the interlocking terminal of the high-voltage plug 

2、 Principle of high voltage interlock

The low voltage monitoring loop should be disconnected first and then connected earlier than the high voltage, and the interval is a certain time (such as 150ms).

 3、Type of high voltage interlock 

      Ⅲ Control strategy

1. Failure alarm

No matter what the state of the electric vehicle, when the high voltage interlock system recognizes the danger, the vehicle should give an alarm prompt to the dangerous situation, and the instrument or indicator should remind the driver in the form of sound or optical alarm, so that the driver can pay attention to the abnormal situation of the vehicle so as to deal with it in time to avoid safety accidents.

2. Cut off the power supply

When the electric vehicle is in the stop state, the high voltage interlock system, in addition to the fault alarm, should also inform the system controller to break the automatic circuit breaker, so that the high voltage source is completely cut off, to avoid the possible high voltage danger to ensure property and personal safety.

3. Power reduction operation

While the electric vehicle is in the process of high-speed driving, and high voltage interlock system in identifying the dangerous situation, it can not immediately cut off the high voltage source, but should first utilize the alarm prompt to remind the driver, and then let the control system to reduce the motor power, so that the vehicle can speed down, and make the vehicle high voltage system run in the case of small load, trying to reduce the possibility of high voltage danger, and allowing the driver to park the vehicle to a safe place.

 IV Example of the high-voltage interlock connection diagram

V High-voltage interlock summary

1. High voltage interlock signal is generally 12V point. It can use the multimeter to detect the off;

2. Interlock signal generation: the signal is generally sent by the VCU, but can also be issued by 15 electricity or BMS;

3. Interlocked signal reception: Interlocked signal is finally received by BMS.