Meaning
Low voltage loop that passes through every high voltage connector and maintenance cover in an electric vehicle system. Disconnecting any component opens the high-voltage interlock circuit and signals the controller to open the main contactors. This hardware based safety feature prevents exposure to lethal voltages during service or accidents.
Circuit Design
Monitoring of the high-voltage interlock occurs at the battery management system or a dedicated power distribution unit. A small current flows through the loop continuously during vehicle operation.
Response Trigger
Detection of an open loop occurs in milliseconds. When the high-voltage interlock signal is lost, the system initiates a rapid discharge of the high voltage bus capacitors.
Protection Level
Design requirements specify that the interlock must be the last to connect and the first to break during the mating of high voltage terminals. This timing ensures that the high-voltage interlock prevents arcing at the main power pins. It also protects the user from accidental contact with live components during rapid maintenance.
In a crash event, the interlock loop is often the first part of the system to fail, which triggers an immediate isolation of the battery energy. This rapid response is a fundamental safety layer in modern vehicle design.
