| 摘要 |
PURPOSE:To prevent an accident from occurring by setting up a compound circuit, consisting of a voltage sensing circuit and a temperature sensing circuit, at the primary side of a ballast, and making a protective device operate according to abnormal voltage build-up or abnormal temperature rise or both. CONSTITUTION:A circuit made up of connecting a relay coil 8 to a parallel connection circuit consisting of a thermister 6 and a resistor 7 in series is parallelly connected to the primary winding 1 to be connected to an AC power source 5. A normally-closed type on-off contact 9 being driven by the relay coil 8 is connected to an interval between this series circuit and the primary winding, while the thermistor 6 is set up in a spot where a temperature rise in ballast winding is sensible. This on-off contact 9 is opened in response to abnormal built-up in supply voltage or an abnormal temperature rise in the ballast winding or both. With this constitution, a fire or the like is preventable. |
