Melbourne-based overhead crane manufacturer Modular Cranes, were presented with an unusual problem. One of their customers, a heavy truck trailer manufacturer, already had two 22-metre-wide overhead cranes installed in their factory which ran on the same set of rails.
These cranes were rated at 12.5 tonnes each, and had given reliable service for many years. They were identical in their specification and were synchronised with both their slow and fast speeds, as well as the elapsed distance they travel to slow down and stop.
The customer's new production process now required that a third crane be included on the same set of rails so that very long and heavy trailers could be moved along the factory with the load shared between two of the cranes at any one time.
A wireless handheld remote control would actuate the pair of cranes simultaneously as required.
The problem facing the team at Modular Cranes was that the existing overhead cranes were no longer available to be sourced.
They needed to look at an alternative that could be installed and synchronised to match the existing cranes.
Importantly, Modular Cranes were looking for a solution that also needed to be economically viable for their customer.
Modular Cranes sought the expertise of NORD Drivesystems for the two travel drive helical geared brake motors on the new crane.
To solve the synchronisation problem, NORD Drivesystems' decentralised frequency inverter technology was also employed.
To enhance the requirement for economy, NORD Drivesytems proposed a conventional four-pole electric motor with a 10Nm electromagnetic brake mounted to each of the NORDBloc.1 series inline Helical geared brake motors.
The three 22-metre-wide overhead cranes share the common rails. All three overhead cranes are synchronised with the slow and fast speeds and also the elapsed distance they travel to stop.
The NORD SK205E series decentralised frequency inverter was also included, complete with internal 24 Volt power supply cartridge, and an external brake resister to accommodate the re-generative current produced by the cranes' weight when slowing to stop.
The high precision accuracy of the NORD Helical gear set and the flexibility of the decentralised frequency inverter software permitted this new crane to synchronised with the existing cranes without the requirement of rotary encoders.
Further, utilising the two decentralised frequency inverters eliminated the need or any shielded cable in this installation.
[Tony Sculpher is Regional Sales Manager Victoria, Tasmania & South Australia, NORD Drivesytems.]