A Novel Technique for Two-Phase BLDC Motor to Avoid Demagnetization

Conventional permanent magnet (PM) motors operate in both magnetizing (pull) process and reversible demagnetizing (push) process on the recoil line of magnets. Therefore, thin-surface PMs may easily undergo a risk of demagnetization at the push process under certain fault conditions, which lead to deterioration of motor performance. Thus, thick magnets, whereas contributing the significantly high cost, are usually used to minimize this risk in the PM motors. In this paper, a novel operation technique, that involves only the pull process, has been proposed for a unique design of two-phase brushless DC motor to avoid the irreversible demagnetization of the magnets. The motor, operated only in the pull process, is kept away from the push process of the operation. Therefore, the motor sustains its initial magnetic operating point above the knee point during the normal operation as well as under the short circuit fault conditions. Finite-element analysis is performed to validate the concept of the proposed technique.