By Vladimir Gurevich
Digital (microprocessor-based) safety relays (DPR) are dominating the worldwide marketplace at the present time, primarily pushing all different sorts of relays out of the image. those units play an essential position in strength operations for fields starting from production, transportation, and verbal exchange to banking and healthcare.
Digital protecting Relays: difficulties and Solutions deals a distinct concentrate on the issues and drawbacks linked to their use, a vital element that is going mostly unexamined. whereas there's already an important quantity of literature documenting the advantages of utilizing electronic relays, units as refined as DPR evidently have faults and disadvantages that must be understood. This ebook covers those, delving into the fewer widely used internal workings of DPR to fill a severe literary void and aid determination makers and experts within the box of security relays locate their means out of the informational vacuum. The ebook presents very important info to aid them in comparing relay manufacturers' claims after which opt for the precise product.
Tearing away the informational "curtain" that exists this present day, this book:
- Describes development of sensible modules of current relays
- Analyzes drawbacks and difficulties of electronic relays
- Details particular technical difficulties and their solutions
- Assesses risks of intentional damaging electromagnetic intrusions
- Discusses substitute (non-microprocessor-based) safeguard relays, and difficulties regarding foreign standards
Focusing on sensible strategies, this ebook explains the best way to accurately pick out electronic relays and confirm their right use whereas warding off the various difficulties they could current. the writer avoids arithmetic and thought in want of simpler, tangible info no longer simply came across somewhere else. environment itself except different books at the topic, this quantity shines a mild into the lengthy hidden "black field" of knowledge on DPRs, giving clients a helpful instrument to aid them expect attainable difficulties, anything sorely missing within the literature.
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Extra info for Digital protective relays : problems and solutions
The gate is a metal plate covering source and drain zones. 1 micron thick. The film of silicon dioxide formed at this high temperature is used as a dielectric. Such film allows us to adjust the concentration of the main carriers in the channel area by changing both value and polarity of the gate voltage. 12). The change of polarity of the bias voltage leads to junction unblocking and to a sharp reduction of the input resistance of the transistor. 11 Symbolic notation of FETs with n and p channels.
28) is used. In this circuit, stable offset voltage is applied to the base of the transistor (T2), and control voltage to base T1. When uinp = uoffset , the currents and voltages in the arms of the circuit are the same. If the input voltage (uinp ) exceeds the offset voltage (uoffset ), transistor T2 is gradually blocked and the whole current flows only through transistor T1 and load resistor RC1, and vice versa. When input voltage decreases below the level of the offset voltage (uinp < uoffset ), transistor T1 is blocked and T2 is unblocked, switching the sole current to the circuit of the resistor RC2.
The upper layer p1 is used as an anode in the thyristor, and the lower layer p2 is used as a cathode. The power circuit is connected to the main electrodes of the thyristor: the anode and the cathode. The positive terminal of the control circuit is connected through the external electrode to the layer p2, and the negative one to the cathode terminal. 39) much resembles the VAC of a diode by form. As in a diode, the VAC of a thyristor has forward and reverse areas. Like a diode, the thyristor is blocked when reverse voltage is applied to it (minus on the anode, plus on the cathode), and when the maximum permissible level of voltage (URmax) is exceeded there is a breakdown, causing strong current and irreversible destruction of the structure of the device.