1. A computer-implemented method for generating an electromagnetic field (EMF) model for an electric device, the method comprising: establishing a time-domain finite data model associated with the electric device, wherein the time-domain finite data model defines a basic system representation of the electric device in the time-domain; utilizing the time-domain finite data model to determine a plurality of responses of the electric device, each response corresponding to a respective one of a plurality of sinusoidal excitations and representing an electrical characteristic of one or more electrical components of the electric device; generating an initial-value problem in the time-domain and representing the basic system representation of the electric device in the time-domain; discretizing at least one time variable in the initial-value problem with a time step, wherein the at least one time variable is discretized to obtain a plurality of discretized time variables of successive time stamps associated with the time step; obtaining a recursive formula associated with the initial-value problem and the discretized time variable; establishing a system matrix equation in accordance with the recursive formula; and generating an EMF model by combining the plurality of sinusoidal excitations using a transformation routine to approximate an input signal, wherein the transformation routine represents each of the plurality of sinusoidal excitations with a plurality of unit step functions to approximate the input signal, and the input signal is approximated as v sin ⁡ ( t ) ≈ ∑ k = 0 K ⁢ [ sin ⁡ ( ω ⁢ ⁢ k ⁢ ⁢ Δ ⁢ ⁢ t ) ⁢ v square ⁡ ( t - k ⁢ ⁢ Δ ⁢ ⁢ t ) ] ⁢ ( Dt ) , wherein ω is angular frequency of the sinusoidal excitation, v square (t−kDt) is equal to a subtraction of step function v step (t−(k+1)Dt) from step function v step (t−kDt), and Δt is time step size, for a wave width of v square (t−kDt); and by combining the plurality of responses, using the transformation routine, to determine an approximate representation of an EMF generated by the electric device in response to the input signal that is approximated from the plurality of sinusoidal excitations, wherein the transformation routine adds and/or subtracts the plurality of responses determined, based on the plurality of unit step functions representing the plurality of sinusoidal excitations, to determine the approximate representation of the EMF generated by the electric device, and the approximate representation of the EMF generated by the electric device is expressed as i ⁡ ( t ) = v s ⁡ ( t - τ ) ⁢ u ⁡ ( t - τ ) ⁢ s ⁡ ( τ ) ⁢ | τ = 0 τ = ∞ ⁢ - ∫ 0 ∞ ⁢ s ⁡ ( τ ) ⁢ d ⁡ [ v s ⁡ ( t - τ ) ⁢ u ⁡ ( t - τ ) ] ⅆ τ ⁢ ⅆ τ , which is i sin ⁡ ( t ) = v s ⁡ ( t - τ ) ⁢ u ⁡ ( t - τ ) ⁢ s ⁡ ( τ ) ⁢ | τ = 0 τ = ∞ ⁢ + ∫ 0 ∞ ⁢ s ⁡ ( τ ) ⁢ V sm ⁢ ω ⁢ ⁢ cos ⁢ ⁢ ω ⁡ ( t - τ ) ⁢ u ⁡ ( t - τ ) ⁢ ⅆ τ when the input signal is 
 v s ( t )= V sm sin(ω t ) u ( t ), where u(t−t) is a step function and s(t) denotes a step function response.