  A representation without explicit use of the isospin formalism is developed
for the precise study of few-nucleon systems, and the advantages of the
proposed approach are demonstrated. Using the example of three-nucleon systems
with central exchange NN-interaction potentials of the general type, the
complete equivalence is shown for the both approaches with and without the
isospin formalism. The new systems of equations contain a less number of
components as compared to the commonly used ones and are more suitable for
precise study of few-nucleon systems, in particular, within variational
approaches. Optimal variational schemes are developed with Gaussian basis, and
the binding energies, r.m.s. radii, density distributions, formfactors, and
pair correlation functions are calculated with a high and controlled precision
for 3H and 3He nuclei.
