SAO PAULO, Dec 5 (Reuters) - Brazilian motor maker WEG plans to invest 1.2 billion reais ($243.45 million) over the next three years to expand its transformer production in Brazil, Mexico and Colombia, the company said on Monday.

The investment will boost the firm's transformer production capacity by around 50%, WEG said in a securities filing. ($1 = 4.9291 reais) (Reporting by Peter Frontini; Editing by Brendan O'Boyle)