To enable overload protection for a motor only by an overcurrent relay.

An overcurrent relay for a motor is constituted of three elements of a long delay operating element, a short delay operating element, and an instantaneous operating element. In this event, because a time-delay operating characteristic b of a protection coordination characteristic for a motor consists of a long delay operating characteristic b-1 and a short delay operating characteristic b-2, even if an interval between a motor start characteristic m1 and a motor thermal limit characteristic m2 is narrow, it is possible to establish the time-delay operating characteristic b between the motor characteristics m1 and m2 without crossing them. Accordingly, overload protection for a motor only by an overcurrent relay becomes possible.