METHOD FOR DIAGNOSING DC MOTOR AND DIAGNOSING JIG

PROBLEM TO BE SOLVED: To prevent the occurrence of flashover in a DC motor. SOLUTION: In a DC motor 50, a ring spring 56 is pressed against a movable clamper 55 while the spring 5 is pushed by a spring retainer 57 from the inside. As a result, the clamper 55 pushes a rectifier 54 through a V mica 53 and holds the rectifier 54 together with a fixed clamper 52. The rectifier 54 holding forces of the clmapers 52 and 55 are adjusted by adjusting the screwing amount of the spring retainer 57 in a tapped hole 52. In the case of performing periodical inspections on the motor 50, the distances din and dout to an inner peripheral position Pin and an outer peripheral position Pout from a reference plane S1 are measured and the difference Δ(=din-dout) between the distance din and dout is found. When the difference Δd is not appropriate, the difference Δd is adjusted to an appropriate value by screwing the spring retainer 57 in the tapped hole 52a, because it is diagnosed that flashover may occur.