A transformer comprises at least two windings and each of the at least two windings includes at least one lead-out wire, and a silicone rubber heat-shrinkable sleeve is wrapped around the outer surface of the lead-out wire. The at least two windings and a portion of the silicone rubber heat-shrinkable sleeve are encapsulated in a potting box with a first potting sealant, and another portion of the silicone rubber heat-shrinkable sleeve is exposed outside of the potting box.