| 摘要 |
<p>Monitoring of trigger circuits of power switches of electrical power supply devices which can experience faults due to breakage of conductors, oxidation of contacts, loosened terminal contacts, short circuits in trigger coils, etc. is described. In order to improve fault monitoring, oscillator oscillations are applied to the trigger circuit of a power switch and are monitored. A fault- or alarm signal is generated in response to a detuning of an oscillator when the detuning persists for a predetermined time. The inductance of the circuit-breaking coil of the power switch serves as a frequencydetermining element of the oscillator. A lag element with a delay of 500 ms is inserted after the oscillator. If the oscillator stays detuned for more than 500 ms, a Schmitt trigger is triggered by the lag element, whereby an alarm relay is actuated which switches on an alarm device via an alarm relay contact.</p> |
