| 摘要 |
Disclosed herein is a safety device for a magnetic field-free heating cable, the heating cable including a first heating wire, a Negative Temperature Coefficient (NTC) thermistor layer wound around the first heating wire, a second heating wire wound around the NTC thermistor layer, a constant melting temperature resin or synthetic-resin insulating layer wound around the second heating wire, a metal shield wound around the constant melting temperature resin or synthetic-resin insulating layer, and an insulating sheath layer wound around the metal shield, the heating cable performing a temperature detection operation during a half cycle of a single-phase two-wire AC power source connected between the first and second heating wires and performing a heating operation during a remaining half cycle. The safety device includes a short circuit detection unit connected in series with the metal shield and connected to a ground side wire, which is one of two wires of the single-phase two-wire AC power source. |
