Static Characteristics of SCR Figure 1(a) shows the circuit symbol and the conventions for the different variables used in the V-I characteristics of the thyristor, shown in Fig. 1(b). The different modes describing the V-I characteristics are as follows: 1. Forward blocking mode: In Fig. 1(b), in forward blocking mode, when gate current IG = […]
Thyristors are a family of semiconductor switches having four or more layers, that is, p-n-p-n type of structure. Nowadays, thyrsitors with blocking voltage in excess of 6 kV and continuous current rating in excess of 4 kA are available. In a thyristor, if the ohmic connection is made to the first p-region and the last
The insulated gate bipolar transistor (IGBT) combines the advantageous features of MOSFET (such as voltage control, fast switching) and BJT (such as low ON-state losses and high OFF-state voltage capability. These devices have near ideal characteristics for high voltage (>100V) and medium frequency (<20 kHz) applications. The IGBT is a three terminal device with Like
Characteristics, Operation, & Construction of IGBT Read More »
A power MOSFET is a metal oxide semiconductor field effect transistor. It is a three-terminal, voltage controlled majority carrier device and has a source lead (S), drain lead (D) and gate lead (G) similar to emitter, collector and base of a transistor, respectively. The movement of the majority carriers in a MOSFET is controlled by
Characteristics, Operation & Construction of Power MOSFETs Read More »
Enhancement Type MOSFETs In this type of MOSFET, channel is formed after applying biasing hence it is named as enhancement type. This MOSFET is smaller in size, economical and provides better performance than depletion MOSFET. Figures 1(a) and (b) depict the cross-sectional view and circuit symbols of n-channel enhancement type MOSFET, respectively. The broken line
Characteristics & Operation of Enhancement Type MOSFETs Read More »
MOSFET stands for metal oxide semiconductor field effect transistor. It is also called IGFET or insulated gate field effect transistor. It is an integrated circuit (IC) or a semiconductor chip. It is fabricated by VSLI using planar technology. The thickness of SiO2 layer is 1000 to 2000 Ao. The larger input resistance of the MOSFET
Characteristics & Operation of Depletion Type MOSFETs Read More »
Instrument Transformers Instrument transformers are used for metering and protection in a power system. Electrical measurements and relaying decisions in a power system are made based on the current and voltage obtained from the system. Relays work with smaller magnitudes of these signals. Real life currents and voltages thus have to be scaled to lower
Distinctive Thermocouple Noise Problems Thermocouple emfs are small. Fine temperature resolution requires substantial amplification. For quasi-static thermometry, modern noise suppression techniques available to designers of data loggers overcome ordinary coupled electrical noise to routinely achieve as small as 0.1 °C temperature resolution and long-term stability (much smaller than required by thermocouple tolerance). Thermocouple measurement of
Thermocouple Thermometry Practice Temperature Ranges Moderate and High Temperatures: Temperature and duration of exposure are unavoidable environmental variables in thermometry. Other environments can sometimes be controlled. Standard thermocouple tables extend only to the greatest temperature of recommended use for benign protected environments, short durations, and for wire materials of 3 mm or greater diameter. Reduced
Calibration of Thermocouples Thermocouple calibration is intended to improve accuracy. Conventional calibration might not. Calibration of a sample from a uniform set of as-delivered thermocouples to confirm conformity to standard tolerance is appropriate. However, despite individual calibration, the approximated standard scaling relation, rather than the actual calibration, usually is used in thermometry regardless of calibration