| Single transformer and double transformer Specification Transformer protector circuitReasons of accident at transformer are error of transformer itself, error of load at the wiring linkage, error of electric power and increase of temperature etc. in my opinion.Error of transformer is directly related with fire and electric shock and proper and adequate measure therefore is required in order to use transformer easily. Particularly, electric current fuse, circuit-protector and protector electric circuit etc, are uSed. When electric current fuse, circuit-protector are selected. Two cases should considered. One is when circuit protector does not operate for input current which is more than ten times of temporary normal current in case of thrust of electric current and the other is when circuit is completely intercepted in case of error. Please select circuit-protector which meet two factors mentioned above at the same time, They are electric current fuse, time-lock fuse and transformer protector with initial feature in terms of circuit-protector. When normal type and high speed type are used. Precautions must be made if it operates in abnormal situation or occurs insufficiently, Method to calculate rated figure of fuse or protector are as below:Rated figure of fuse the first normal electric current of transformer/0.7~0.8The first normal electric current of transformer=rated capacity/(efficiency*input voltage)-refer to the table on the right hand side in terms of efficiency. When wy21-1kva(single phase 1KVA) is used as rated capacity at input voltage 220V.The first rated electric current = 1000W / (0.93*220V)=4.89With regard to rated value of fuse to be designed = 4.89A/0.7~0.8=7-6ATerminal block dimension & specification | 
