Starting from the two operational states of permanent magnet

this article explains that the working point of permanent magnet in the permanent magnet actuator is sited on the reversional curve

and the demagnetized curve of NFeB permanent magnet is approximately in a straight line

and its reversional curve coincides with the demagnetized curve

moreover

its flux density has repeatability. It is proved that the demagnetization wouldn’t happen in the permanent magnet actuator with singlecoil during the operation of circuit breaker.