When does a transformer need a fuse? Is not an appliance that converts low voltage to high voltage and vice versa? The answer lies in the fact that even the transformer is an electrical appliance and can short circuit in case of being overloaded. Usually a transformer is an expensive unit that takes care of home and commercial appliances. The fuse is a small device that takes care of the transformer in return. These are not at all expensive to buy and for a few dollars, you can get a whole pack of these. Visit Sam Stores to order this fuse now.