The mechanical lock between the two contactors prevents one of the contactors from switching on, as long as the other is still switched on and vice versa.
Switching over reversing contactors too quickly poses the risk of a phase short circuit.
This is the case if the arc of the contactor switching off has not yet extinguished and the contacts of the contactor switching on are already closed.
To avoid this risk, the two contactor coils must be switched to idle for a minimum of 50 ms during the switchover process and electrically locked against each other.

Want to show harmful overcurrent who's boss? Get this MCB from ABB on your team. It breaks an attached circuit in the event of excess current to prevent injury to users and damage to equipment. A broad operating temperature range between -25°C and +55°C makes it a reliable option for harsh work areas. Simple screw terminals mean it's simple to install without special tools. For added flexibility, the unit's can be mounted in any position. With a maximum voltage rating of 440V AC and a 16A current, this MCB's safe to use in powerful electrical systems.

• Tested up to 4kV for reliable protection against impulse voltages
• Tightening torque of 2.8Nm means it's simple to install by hand
• DIN rail mounting design for convenient snap-on setup
• IP20 rating means it's touch-proof and shielded from objects larger than 12mm
• Light weight of 225g so it won't strain your rail

• Domestic circuitry
• Consumer units
• Distribution boards

This compact product measures 69 (L) x 35 (W) x 88mm (H), so it saves space in a busy system.