Reversing Contactor

A Reversing Contactor is a specialized electromechanical system consisting of two interlocked contactors designed to reverse the direction of a three-phase motor. It works by swapping two of the three power phases supplied to the motor. One contactor connects the phases in one order (e.g., L1, L2, L3) for forward rotation, while the second contactor swaps two phases (e.g., L1, L3, L2) for reverse rotation. A mechanical and electrical interlocking system ensures only one contactor can be energized at a time, preventing dangerous short circuits.

The primary application is for bi-directional motor control. They are essential in any machinery where a motor needs to run in both forward and reverse directions.

Common examples include:

• Hoists and Lifts: For raising and lowering loads.
• Conveyor Systems: For reversing direction to clear jams or manage material flow.
• Machine Tools: For automatic reverse feed in lathes, milling machines, or drilling machines.
• Opening/Closing Mechanisms: Such as gates, doors, and valves.

Interlocking is a vital safety feature. Because both contactors are connected to the same power supply, if they were to close simultaneously, it would cause a severe phase-to-phase short circuit. Interlocking, which can be mechanical (via a lever system), electrical (via auxiliary contacts), or both, physically and logically prevents both contactors from being closed at the same time, protecting the equipment and personnel.

A standard contactor is a single unit used to switch a motor on and off. A Reversing Contactor is essentially two standard contactors packaged together with an interlocking mechanism. This integrated design is specifically engineered for the complex and safety-critical task of reversing motor rotation, providing a more compact and reliable solution than two separate, non-interlocked contactors.

While it is theoretically possible, it is highly recommended to use a pre-assembled KRIPAL Reversing Contactor unit. These are factory-configured with certified mechanical and electrical interlocking, ensuring maximum safety and reliability. Building your own assembly requires careful engineering to implement a failsafe interlock, which, if done incorrectly, carries a high risk of catastrophic failure.

Key selection factors include:

• Motor Power: Ensure the contactor's rated operational current and voltage match or exceed your motor's specifications.
• Utilisation Category: Look for categories like AC-3 (for squirrel-cage motors) and AC-4 (for frequent plugging and inching).
• Coil Voltage: Match the coil voltage (e.g., 24V DC, 230V AC) to your control circuit.
• Safety Features: Verify the type of interlocking (mechanical & electrical) and the availability of auxiliary contacts for control feedback.
• Space: Check the physical dimensions to ensure it fits in your control panel.

KRIPAL Reversing Contactors are engineered for performance and safety:

• Robust Interlocking: A failsafe mechanical and electrical interlock prevents both power contactors from closing simultaneously.
• Durable Construction: Silver alloy contacts with excellent arc resistance ensure a long electrical life, even under frequent switching.
• Easy Installation: Pre-assembled units with clear wiring diagrams simplify panel building and save time.
• Compliance with Standards: Manufactured in accordance with international standards like IEC 60947-4-1, guaranteeing safety and performance.
• Reliable Operation: Designed for the demanding conditions of industrial motor control, providing consistent and safe reversal of motor direction.