Hysteresis Cable Reels for Port Cranes: Working Principle & Installation Guide

Overview

1. Introduction to Hysteresis Cable Reels

A hysteresis cable reel is a specialized power supply device used for large mobile lifting equipment traveling on rails. It is widely applied in portal cranes, container cranes, and other heavy machinery in ports.

Compared to counterweight or torque motor reels, hysteresis reels offer:

• Compact size and full functionality.
• Constant tension characteristics for cable protection.
• Adjustable torque based on site conditions.
• Braking capability without needing an external brake.
• Long-term stall capability without damage to the motor.

2. Structure and Magnetic Coupling Principle

Internal Components: The system consists of the cable drum, planetary gears, conical gearbox, collector (slip ring), hysteresis coupling, and an electric motor.

How the Hysteresis Coupling Works: The coupling consists of multiple permanent magnets creating a multi-pole field and an induction disk. When the motor drives the induction disk at high speeds, magnetic coupling rotates the disk. Any speed difference (slip) creates a torque that resists the slip. This non-contact magnetic connection allows for smooth driving or braking.

3. Operational Principle

• Unwinding (Payout): When the crane moves away from the power source, the cable is dragged. This overcomes the magnetic torque, creating a slip between the disks. The magnetic field ensures the cable remains tensioned during payout.
• Winding (Retraction): When the crane returns, the dragging force is removed. The motor (which always rotates in the winding direction) takes up the cable.
• Inertia Protection: If the crane stops suddenly, a one-way clutch (backstop) inside the coupling keeps the motor locked while the drum continues to rotate slightly due to inertia, maintaining 80% of the stall torque to prevent cable slack.

4. Installation & Commissioning Best Practices

• Alignment: The center of the cable tray, the guide device outlet, and the ground cable trench must be on the same vertical line.
• Bending Radius: The distance between the guide device and the drum, and the height above ground, must exceed the cable's minimum bending radius.
• Waterproofing: After wiring, ensure all glands (motor, slip ring box) are sealed for waterproofing.
• Phase Sequence: Motors must rotate in the specified direction. Never change the phase sequence or use reverse-current braking, as this will damage the internal one-way bearing.

5. Maintenance in Harsh Environments

Since these reels work in high temperature, humidity, and salt spray environments:

Verify that cable connections are tight and free of corrosion.

Regularly lubricate gearboxes and planetary gears.

Check the slip ring and carbon brushes to ensure they are clean, dry, and making good contact.