A 1 0-A time-delay fuse is the maximum size permitted
to protect the 3-k VA transformer. Time-delay fuses an
used when the over current device is sized at less than
15 A.
The over current device protecting the primary of transformer is permitted to be sized as large as 2. 5(
(250%) times the primary full-load current, provided the
transformer secondary is also protected, Figure 14-25
The transformer secondary over current device is sized a
1.25 (125%) times the secondary full-load current. Th'
next size larger over current device is permitted except
where the secondary current is less than 9 A. In this case, the over current device is not permitted to be large
than 1. 67 (167%) times the transformer secondary circuit.