Fuse blown indicator. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Protection of equipment from emergency operation of the network
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To protect electronic equipment from current overloads, fuses and thermal fuses are used. After the fuse trips, the equipment is inoperative, so a timely response to the protection operation allows you to quickly eliminate the cause of the malfunction and start the equipment again.
The proposed device indicates a blown fuse with short sound and light signals.
The indicator is made in the form of a two-pole connected in parallel to the fuse in a DC or AC circuit with a frequency of up to 1 kHz and a voltage of 10 ... 1000 V. The device includes a current limiter on resistors R1 and R2, a bridge diode rectifier (VD1 ... VD4), elements of sound (BQ1) and light (HL1) indication and negatron, made on transistors VT1, VT2 and resistors R3, R4.
As a time-setting capacitor, the device uses a BQ1 piezoceramic emitter, which, if only LED indication is used, can be replaced by a capacitor with a capacitance of 0,022..,0,5 μF.
When the fuse blows, the mains voltage is applied to the indicator, and the device generates intermittent light and sound signals (clicks). It is assumed that the load resistance is finite and does not exceed a few megaohms. To indicate a blown fuse with an open load, a resistor with a resistance of 1 ... 2 MΩ can be connected in parallel with RH. The residual current flowing through the load and the indicator at a mains voltage of 220 V does not exceed 0,5 mA.
Authors: M. Shustov, A. Shustov, Tomsk; Publication: N. Bolshakov, rf.atnn.ru
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