ABNORMALITY DETECTOR OF GROUND COIL FOR MAGNETIC LEVITATION TYPE RAILROAD

PURPOSE:To enable the detection of aging of insulation of a ground coil beforehand by providing at least more than one high frequency current transformers on a earth wire of the ground coil to connect the secondary side thereof to a differential amplifier. CONSTITUTION:A coil conductor 2 is covered with an insulation layer 3 and a high frequency current transformer 9 is disposed on an earth wire 8 for connection between earth layers of a ground coil 1, which is provided with the earth layers on the surface thereof. When outputs of at least more than current transformers 9 are connected to a differential amplifier (D. AMP) and an HPF, currents i1, and i2 flow to the current transformers 9 having a current associated with a frequency component of an operation voltage overlapping a current of a pulse-like high frequency component accompanied by an aging of insulation. When the currents are inputted into the D.AMP, as an electrostatic capacitance of the coil 1 is almost equal in capacity, the current corresponding to the frequency component of the operation voltage is canceled to be almost zero and the pulse-like high frequency component alone is left, so that the current is associated with the aging of the insulation is detected from HPF. This enables the detection of the aging of the insulation of the coil 1 beforehand thereby achieving a rationalization of manufacture and higher safety of the operation of a vehicle.