| 摘要 |
PROBLEM TO BE SOLVED: To provide an earth fault detector of higher safety and a medical diagnostic instrument therewith by quickly detecting an earth fault, if it occurs in an apparatus, for cutting power supply for keeping instrument leakage current at or below a prescribed value. SOLUTION: A phase current detecting means (22) is disposed between a commercial AC power supply (7) and a noise filter (8) connected to the commercial AC power supply line to detect current for each phase, and the detected value is inputted into a current summing means (23) to obtain the summed value of current in each phase. The summed value is compared with a reference value Vref in a comparison mean (25) and, if the summed value is at or above the reference value, an earth fault is determined to detect the earth fault caused by bringing non-insulated part inside an instrument into contact with an outer cover or a case. An earth fault detecting device formed as this is used in medical diagnostic instruments including an X-ray high-voltage generator and an X-ray diagnostic instrument therewith, an X-ray CT instrument, a magnetic resonance imaging instrument, and an ultrasonic diagnostic instrument to detect an earth fault. The detection signal stops the operation of an instrument and gives notice of the occurrence of the earth fault, thereby improving safety of medical diagnostic instruments.
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