Pyrofuse or Pyroswitch and how does it works?

 

Pyrofuse or Pyroswitch 

The "pyro" part refers to the small explosive charge within the device.

When triggered, this charge detonates, breaking a connection within the fuse and interrupting the electrical circuit.

This process happens very rapidly, within milliseconds after the collision and triggered by the VECU of an electric vehicle.

Pyro switch or Pyro fuse is an electrical fuse that uses a small explosive charge to quickly and permanently cut off the flow of current in a circuit.

This is typically used in high-voltage battery systems, such as those found in electric vehicles, to prevent fires or other hazards in the event of a crash or short circuit.

Pyro switch function:

• Initiator: This is the small explosive charge. When an electrical signal is sent, it ignites.
• Gas Generation: The explosion creates a rapid expansion of gas.
• Piston: The force of the expanding gas pushes the piston. This piston is the key to how the switch works.

How this translates to a pyro switch:

1. Enclosure: All of this would be contained within a robust, insulated enclosure (likely plastic or ceramic). This enclosure would be the visible "pyro switch" itself.
2. Terminals: The enclosure would have electrical terminals connected to the circuit that needs to be interrupted.
3. Piston Action: The piston's movement is used to break the electrical connection. There are a couple of ways this could happen:
• Direct Break: The piston could directly separate two electrical contacts, physically opening the circuit.
• Cutting Element: The piston could drive a small cutting element (like a blade) that severs a conductive link within the switch.

Structure of the Pyro switch:

Internal Structure of Autoliv Pyro Saftey switchs

                                                                                      

Imagine a small, rectangular or cylindrical box.

• Casing: The outer casing is made of a dark-coloured, robust plastic or ceramic.
• Terminals: Two or more metal terminals protrude from the casing.
• Internal Mechanism (Invisible): Inside, the initiator, gas generation chamber, and piston are arranged as shown in your image.
• External Indication (Possible): There might be a slight bulge or a line on the casing indicating where the piston moves internally. After activation, this area might be visibly deformed or cracked.