  We give explicit formulas for the elements of the center of the completed
quantum affine algebra in type $A$ at the critical level which are associated
with the fundamental representations. We calculate the images of these elements
under a Harish-Chandra-type homomorphism. These images coincide with those in
the free field realization of the quantum affine algebra and reproduce
generators of the $q$-deformed classical $W$-algebra of Frenkel and
Reshetikhin.
