I know there are 3 phrases used to describe exhibition/fair, namely "博览会", "交易会" and "展销会". Can those phrases be used interchangeably or is there any difference for each specific phrase?
博览会, 交易会 and 展销会 can be used interchangeablely. All of them mean "exhibition". They are synonyms, different only in literal meanings.
The literal meanings are:
博览会 broad viewing party
交易会 trade party
展销会 display and sales party