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The work is devoted to some problems in numerical modelling plasma generated in the course of magnetic implosion of multiwire arrays (liners) in Z-pinch discharge mode, including numerical and theoretical analysis of quasispherical imploding conical wire arrays. Experiments were performed at ANGARA-5-1 facility (TRINITI) with the discharge current up to 3 MA. The numerical simulations were carried out on the base of 2D RMHD code MARPLE (IMM RAS). An appropriate description of the early phase of plasma generation during the electrical explosion of wires is a real challenge in MHD modeling of these experiments, in our computations we used the plasma ablation model, which allows to obtain more realistic results as compared with the models where the entire wires are considered to be initially already in plasma state. According to the experimental data we assume that the wire skeleton is stable during the overall time of the plasma generation as its density is significantly more than that of the surrounding plasma. Besides that the skeleton carries essentially less electric current than the plasma. The plasma ablation process lasts until the total wire skeleton evaporation. Experiments show that in the case of current pulse matched load the plasma generation is finished soon after the current maximum. Taking into account small diameter of the wires as compared with interwire gaps and the array dimensions plasma production is simulated by a steady source surface placed inside the computational domain. The mass ablation rate at the unit of the source surface is calculated with respect to the local distribution of the magnetic field induction. The numerical experiments showed that the plasma ablation model has a significant effect on both the entire scheme of plasma dynamics and such values as voltage drop at the load and soft X-ray yield power. The improvement of the ablation model parameters based on experimental and theoretical estimations is an issue of the day in 2D and 3D Z-pinch simulations.