What is the principle of permanent magnet crane?

What is the specific principle of the permanent magnet crane that can be realized by pulling the switch from left to right?

Principle of permanent magnet lifting device: The permanent magnet lifting device developed by using NdFeB permanent magnet material can overcome the above shortcomings of electromagnetic lifting device and make a major change in the permanent magnet lifting technology. The permanent magnet lifting device is designed by using the continuity principle of magnetic flux and the superposition principle of magnetic field. The magnetic circuit of the permanent magnet lifting device is designed into multiple magnetic systems. Through the relative motion of the magnetic system, the magnetic field strength on the working magnetic pole surface is added or eliminated, so as to achieve the purpose of working and unloading.

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