This paper is meant to bring the readers’ attention to a strange curious result concerning the wye/delta (or T/Pi) conversion. The interesting result we have never seen reported in the literature is that negative resistors may be needed for modeling passive unbalanced three-phase load impedance.
The seed for this research was a recently published paper on nonuniform multiconductor transmission power lines where the analysis of load matching conditions (employing ordinary networks of partial-admittances, led to numerical evidence of negative load resistors despite the whole MTL system being passive and reciprocal.
Here we show that the presence of unrealizable negative load resistors in three-phase systems is mathematically possible without violating any physical principle, illustrative examples being offered.