| 摘要 |
An indicating device for use in a plant for supplying electric current from an alternating current source to a loop circuit having a plurality of serially interconnected primary circuits of a number n of current transformers coupled to an airfield lighting lamp, comprises a transformer coupled to the alternating current source to generate a voltage signal representative of the voltage supplied to the loop circuit, a transformer coupled to the loop circuit to generate a current signal representative of the current flowing in the loop circuit, and an electronic circuit capable of generating in response to the voltage and current signals an output voltage indicative of the number of primary circuits of the loading transformers being uncoupled to their respective secondary circuits. The output voltage is proportional to the voltage integral. <IMAGE> of the loop supply voltage u from the time to when the loop current i in each half period passes the zero value and to the time T when the loop current i attains a value corresponding to the saturation current iM for the current transformers. Preferably, a compensation voltage representative of the value of the voltage integral in case none of the current transformers has an unloaded secondary circuit is subtracted from the output voltage so as to obtain a final voltage signal which can be passed on to a meter precalibrated to indicate the number of uncoupled secondary units. |
