The voyager probe has now been locked on to alpha centauri...how long at its current speed will it take to get

The star Voyager 1 is going to come the closest to would be AC+79 3888, a star in the constellation of Camelopardalis. Voyager 1 will be within 1.6 lightyears or 9.3 trillion miles of AC+79 3888 in about 40,000 years. The star Voyager 2 is going to come the closest to will be Sirius, the brightest star in the sky in the constellation Canis Major. It's closest distance to Sirius will be 4.3 lightyears or 25 trillion miles it will reach this point in about 296,000 years. Neither one is scheduled to come close to Alpha Centauri in the constellation Centaurus

OK, assuming Voyager 1 is locked onto Alpha Centauri, which it's not;

According to heavens-above.com, Voyager 1 is travelling at 17,048 m/s - equivalent to 3.596 AU / yr.
According to Wikipedia, Alpha Centauri is 4.336 ly, or 1.339 pc ~ 276,000 AU

So the approximate time is 276000 / 3.596 ~ 77,000 years

Note however that, Voyager 1 would require a course change of about 80º. It would also continue to slow down as it leaves the Sun's gravitational well.

There is no way that either of the Voyager probes could be redirected to Alpha Centauri. They are going where they are going, period.

Neither Voyager 1 nor Voyager 2 is aimed at Alpha Centauri.