The positive magnetic port is based on the MagneticPort. Additionally the reference angle is specified in the connector. The time derivative of the reference angle is the actual angular frequency of the quasi-static magnetic potential and flux. The symbol is also designed such way to look different than the NegativeMagneticPort.
MagneticPort, NegativeMagneticPort, Magnetic.FluxTubes.Interfaces.PositiveMagneticPort