ABB VM19 Voltage Monitoring Relay

The ABB VM19 Mechanical Interlock Unit is a mounting accessory for ABB AF-series low-voltage contactors that provides a mechanical interlock between two adjacent, equal-size contactors to prevent simultaneous energization. It is designed for contactors AF116 through AF370, and is commonly ordered as 1SFN030300R1000. When installed between two equal-frame contactors, the VM19 enforces sequential operation, making it ideal for motor-control panels and circuits that require interlocked switching or reversal configurations. Being a purely mechanical device, it does not rely on electrical signals to function and integrates with ABB’s interlock accessories to deliver a compact, maintenance-free solution within ABB low-voltage switchgear. Typical applications include safeguarding dual-contactor starters in machinery and process lines where one contactor must remain de-energized while the other operates, ensuring safe handover and preventing both contacts from closing at once. The VM19 interlock complements ABB’s AF-series ecosystem, helping to simplify panel wiring and improve safety without additional control logic. Compact form factor suits tight enclosures.