Sensorless Magnetization Current Control for Stable Connection and Separation of Electropermanent Magnet

An electropermanent magnet (EPM) can be connected to and separated from ferromagnetic materials by reversing a magnetization state of an AlNiCo magnet. This paper proposes a sensorless magnetization current control for a stable operation of the EPM. Its state of connection and separation is estimated from an induced voltage in the EPM's coil. A current phase control is constructed by detecting a positive-going zero crossing of the induced voltage.