Given wrong charger for 15 inch MacBook Pro

I was given a 61 W charger for my 15 inch MacBook Pro. I always thought this was the correct charger because I never had a problem. Recently I plugged it into the wall and into my MacBook and it started to smoke and completely burned my charger and almost started a fire. I would like to know why I was given the wrong wattage charger and what I can do to replace the one that malfunctioned.