An Electronic Replacement for Thermo-Mechanical Load Protection Devices

An electronic replacement for the thermo-mechanical overcurrent protection devices for ac loads is sought. The proposed scheme works on a principle of integrating certain width- and amplitude-controlled line current ``error´´ signals and it is shown to be capable of having variable overload protection characteristics. Facility for protection of loads against unbalance is also incorporated in the scheme. A simple hardware implementation is given and the results obtained thereof are found to be satisfactory. It is concluded that such a scheme would be commercially viable.