Abstract
The braking effect of hoists is influenced by the efficiencies of the installed components. It is foreseeable that the occurring losses lead to greater decelerations than lossless consideration. This article considers the efficiency and its description. He goes from an easily comprehensible description for a simple mechanical system for the description of a hoist with its temporally and locally variable energy inputs and energy outputs. The article presents a general equation for the system acceleration of hoists. This general equation potentially takes into account three brakes: motor brake, service brake and safety brake and two efficiencies: Gearing efficiency and rope drive efficiency. Finally, the braking distances and the required braking torques for braking with the safety brake of the reference hoist are shown. The contents are inspired by the VDI Technical Committee 304 Cranes.
Highlights
A characteristic feature of mechanical drives is loss
When the kinematic variables are coupled via fixed ratios, the loss manifests itself in a reduction in static magnitudes, e.g. the torques in rotation systems:
The locations of the power supply and the energy extraction are located at one end of the drive train each
Summary
A characteristic feature of mechanical drives is loss. For many systems with loss the situation is quite clear They have only one position of energy supply to the system (engine) and only one position of energy extraction from the system (machine). The locations of the power supply and the energy extraction are located at one end of the drive train each. The power flow direction is not that obvious at least in certain parts of the powertrain. This applies subsequently to the relationships of the different amounts of energy expressed in terms of efficiency. With low efficiency components involved, this is of interest in terms of the resulting brake dimensions and braking distances due to e.g. Emergency stop and off due to response of the hoisting limit switch
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