As the name suggests, electric cranes are a type of crane that are operated electrically. Electric cranes are used for construction, material handling and other similar functions. These cranes use AC power drive technology, which has slip ring induction motor whose rotor windings are connected to power resistance in 3-5 steps by power contractors. In electric cranes multi motor drives are used very often and in this case proportional share of power between motors is very important.
Different types of electric cranes are EOT cranes, Electric Jib cranes, Electric controlled gantry cranes, Offshore/ cranes, Tower cranes and Luffing cranes. Electric cranes are enabled with two types of safety or emergency switches for avoiding any kind of accidents; these are Maximum load limit switch and Load moment limit switch.
The main function of maximum load limit switch is to cut the electricity supply, whenever the load exceeds the specified capacity of the crane. This switch along with other accessories, monitors the pull (strain) on the cable. If a crane crosses the load limit, then this switch trips the motor and gives audio and visual alarm. On the other hand, load moment limit switch along with other accessories ensures the load moment (tonne- meter) rating does not exceed beyond the specified limit. If a crane crosses the given limit, then this switch trips hoist motor and traversing motors with audio and visual alarm.
Tips to follow while operating electric cranes are :
Do not operate electric cranes unless you have been trained for safe operations.
Make sure guards, safety signs and other safety features are in right place and in good condition.
Read, understand and follow the crane load capacity manual and work area chart.
Keep three wraps of load line on winch.
Operate crane controls slowly and smoothly.
Know the position of the booms while operating the crane.
Eliminate swing by positioning the boom tip directly over the center of the load before lifting.
Salient Features :
Attributes of bridge cranes owing to which these are appreciated and demanded are :
Sturdy design, compact in size and user-friendly
Easy installation and little maintenance
Resistant to corrosion, wear and abrasion
Weather proof, UV rays resistant and can resist heat and high temperature
Low electricity consumption and impeccable performance
Unmatched efficiency and noiseless operation