Proposed Preventative Measure against Failures of Electromagnetic Lifter

Briefed in the paper are imported electromagnetic lifers for tube/scrap steel handling of Tianjin Pipe (Group) Corporation, focusing on the work principle and output characteristics of the lifer-employed SF1-LS304 frequency relay and common failures thereof. Also discussed are the proposed preventative measure involving employment of the frequency relay to check the rotor frequency of the scrap steel-handling lifter's wound-rotor asynchronous motor to prevent the lifter from failures by means of "reversed braking current" control, "lowering with extra-synchronous speed" as well as "stopping re-lifting".