This paper investigates the impact of current phase difference between the primary and auxiliary coils in an Electromagnetic Halbach Array (EHA) on its magnetic field distribution. Unlike conventional in-phase excitation, phase-shifted driving significantly alters the magnetic field characteristics and affects power transfer efficiency. To efficiently analyze this effect, a modeling approach based on vector magnetic potential under the magnetoquasistatic regime is proposed, enabling fast prediction of sinusoidal magnetic field distributions under static current inputs. The model demonstrates strong agreement with Ansys simulations across multiple spatial regions and heights, and is further validated through experimental measurements. Results show that the magnetic field strength decreases monotonically with increasing phase difference, with the theoretical model, simulation, and experimental data exhibiting excellent consistency in both trend and magnitude. Therefore, in practical EHA applications, the primary and auxiliary coils should be driven in-phase to achieve optimal magnetic field performance and transmission efficiency.