  This paper presents the constraints on the time variation of the fine
structure constant at recombination relative to its present value, Delta_alpha
= (alpha_rec-alpha_0) / alpha_0, obtained from the analysis of the WMAP-3yr
Cosmic Microwave Background (CMB) data, with an additional prior on the Hubble
expansion rate from HST Hubble Key Project. I found out that -0.039 <
Delta_alpha < 0.010 at 95% C.L., which brings a 30% improvement to the previous
limits from WMAP-1yr data. The corresponding recombination redshift, 1012 <
z_rec < 1115, shows a delayed recombination epoch compared with the results
from WMAP-1yr data.
