Appliance for measuring alternating current which saturate the current transformer core using secondary currents up to saturation point

摘要

The appliance has current transformers (17a,b,c) with primary windings (7a,b,c) for the a.c. current and secondary windings (21a,b,c) which provides a secondary current proportional to the primary current and cores (19a,b,c) coupling the primary and secondary windings. At the high end of the nominal dynamic current range the current saturates the core. An A/D converter (23) detects the secondary current and a microprocessor (25) converts it to an output signal which represents a selected measurement of the a.c. current up to the point when the core saturates. The appliance can be provided with a system which produces the output signal in the form of an RMS current