Lightning or surge arresters serve the same purpose on an electric circuit or line as a safety valve on a boiler. A safety valve on a boiler relieves a high pressure by allowing steam to blow off until the high pressure is reduced to normal, at which time the safety valve closes again and is […]
The base speed listed on a DC motor’s nameplate is an indication of how fast the motor will run with rated armature voltage and rated load amperes at rated field current. DC motors can be operated below base speed by reducing the amount of voltage applied to the armature and above base speed by reducing
Unlike a brush DC motor, a brushless DC (BLDC) motor, as the name suggests has no brushes. Because there are no brushes, a BLDC motor produces little electrical and acoustic noise, and does not suffer from the wear of brushes and the need to replace them periodically. Thus a BLDC motor is more reliable than
TRIAC (Triode thyristor for alternating current) or triac is a bi-directional thyristor switch mainly used for AC control applications. It conducts in both directions, unlike the thyristors (SRCs) which conduct in one direction only. It can be considered to be equivalent to two thyristors connected in anti-parallel but having only three terminals. It has a
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
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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
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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
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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
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