Hoist inverters, or variable-frequency drives (VFD), are the secret to safety for crane hoists. While not technically a secret, hoist inverters and their software do run quietly in the background, making crane operation easier, smoother and safer—even for less experienced operators.
By Greg Williams, Field Support Specialist
Enabling smooth operation and steady load control compared to the contactor controls they replace; hoist inverters reduce mechanical wear. And with the smoother operation comes improved crane safety. The following are some of the major safety features that can be programmed into hoist inverters, including those offered by Konecranes:
Sway control prevents loads from swinging, helping even relatively inexperienced operators maintain safe, steady control of a load. This feature allows operators to focus their attention on their surroundings, helping them choose a safe travelling path for the load.
Brake slip detection assures that the holding brake of the hoist has the necessary amount of torque to effectively hold the load. When torque is insufficient, brake slip detection sends current to the hoist motor to hold the load. Additionally, this feature sounds an alarm to alert the operator to the situation so that they can safely lower the load to the ground and prevent the potentially dangerous consequences of a dropped load.
Shock load prevention reduces structural stress on an overhead crane and runway when an operator attempts to lift a load in an abrupt, aggressive manner. This minimizes potential damage to the crane, load, runway and building supports. When shock load protection detects an abrupt lift, it automatically slows the hoist motor. This allows slack chains and slings to tighten before the hoist returns to full speed to continue the lift. Besides promoting safe crane operation, this feature reduces maintenance costs and can extend the life of the crane.
Overload detection monitors loads to detect when they exceed the rated capacity of the crane. When this feature detects an over-capacity load, it prevents the lift.
Slack rope prevention prevents damage to spreader beams and hoists, as well as unsafe conditions around the load zone. It does so by detecting when a load reaches the ground. It then stops the downward motion of the hoist, preventing a spreader beam from falling.
While many crane manufacturers add inverters to hoists, Konecranes differentiates itself in the overhead crane market by designing and building variable frequency drives (VFDs) and software specifically for hoisting applications. Konecranes Service can add VFDs to an existing crane as a retrofit.
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