  We analyze the formation mechanism of three homologous broad coronal mass
ejections (CMEs) resulting from a series of solar blowout-eruption flares with
successively increasing intensities (M2.0, M2.6, and X1.0). The flares
originated from active region NOAA 12017 during 2014 March 28-29 within an
interval of approximately 24 hr. Coronal magnetic field modeling based on
nonlinear-force-free-field extrapolation helps to identify low-lying closed
bipolar loops within the flaring region enclosing magnetic flux ropes. We
obtain a double flux rope system under closed bipolar fields for the all the
events. The sequential eruption of the flux ropes led to homologous flares,
each followed by a CME. Each of the three CMEs formed from the eruptions
gradually attain a large angular width, after expanding from the compact
eruption-source site. We find these eruptions and CMEs to be consistent with
the 'magnetic-arch-blowout' scenario: each compact-flare blowout eruption was
seated in one foot of a far-reaching magnetic arch, exploded up the encasing
leg of the arch, and blew out the arch to make a broad CME.
