| 摘要 |
PROBLEM TO BE SOLVED: To provide an insulation diagnostic bridge circuit capable of measuring a detection signal in a safe state without applying a high voltage to a measuring instrument and capable of measuring the insulation characteristic of a test dielectric substrate without being affected by the harmonic waves included in a voltage source. SOLUTION: This insulation diagnostic bridge circuit is provided with a current transformer 5, which comprises a primary winding 7 connected in series to a standard capacitor 2 and wound on a transformer core 6 at a variable number of turns, a test high-voltage cable 10 differentially connected to the primary winding and serving as a secondary winding penetrating the transformer core, and a tertiary winding 14 connected to a current analyzer 15 and wound on the transformer core, and a power supply 1 applying a high voltage to the current transformer 5. By adjusting the number of turns, current, and phase of the primary winding, the fundamental wave components of the charging current and loss current of the primary winding and the secondary winding are balanced, and the fundamental wave current component of the tertiary winding is negated. The harmonic wave unbalanced component flowing in the secondary winding is detected by the tertiary winding and fed to the current analyzer for an insulation diagnosis of the test high-voltage cable.
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