CIRCUIT DIRECTORY

Silicon Controlled Rectifier (SCR) Silicon Controlled Rectifier (SCR) It  is a unidirectional semiconductor device made of silicon which can be used to provide a selected power to the load by switching it ON for variable amount of time. These devices are solid-state equivalent of thyratrons and are hence referred to as thyristors or thyrode transistors. In fact, SCR is a trade name of General Electric (GE) to the thyristor. Basically SCR is a three terminal, four-layer (hence of three junctions J1, J2 and J3) semiconductor device consisting of alternate layers of p- and n-type material doping. Figure 1a shows the SCR with the layers pnpn which has the terminals Anode (A), Cathode (K) and the Gate (G). Further it is to be noted that the Gate terminal will generally be the p-layer nearer to the Cathode terminal. The symbol of the SCR used in case of circuit diagrams is shown in Figure 1b.  These SCRs can be considered equivalent to two inter-connected transistors a

How electricity is produced? Each and every one of us depends on electricity to smoothly move through our day. Our cell phones, laptops and countless other appliances run on electric power. Our need for electricity is overwhelmingly apparent and especially realized when something goes wrong – which is most likely when you give us a call! You know you need electricity, but do you know what it really is or how it’s produced? Join Electrical mastar as we get back-to-basics and take a closer look at the electricity that powers our lives. What is Electricity? Before delving into how electricity is produced, let’s begin with a little “Electricity 101.” To put it simply, electricity is the flow of electrons from one place to another, more specifically flowing around a circuit. You can probably think back to your high school chemistry class (with either fondness or disgust – there’s not much in between!) where you learned about atoms, or the “building blocks of life.” Electrons are

Basic Electrical Theory  Electrical charges:-   Charge is an electrical property of the atomic particles of which matter consists, measured in coulombs (C).  • The charge e on one electron is negative and equal in magnitude to 1.602 × 10-19 C which is called as electronic charge. The charges that occur in nature are integral multiples of the electronic charge.   Electrical Current:-  Electric current i = dq/dt. The unit of ampere can be derived as 1 A = 1C/s. • A direct current (dc) is a current that remains constant with time. • An alternating current (ac) is a current that varies sinusoidally with time.   Example 1  A conductor has a constant current of 5 A. How many electrons pass a fixed point on the conductor in one minute? Solution Total no. of charges pass in 1 min is given by 5 A = (5 C/s)(60 s/min) = 300 C/min Electric Voltage:- • Voltage (or potential difference) is the energy required to move a unit charge through an element, measured in volts (V

What is Electrical Drive? Types of electrical drives? Electrical Drive: Whenever the term electric motor or electrical generator is used, we tend to think that the speed of rotation of these machines is totally controlled only by the applied voltage and frequency of the source current. But the speed of rotation of an electrical machine can be controlled precisely also by implementing the concept of drive. The main advantage of this concept is, the motion control is easily optimized with the help of drive. In very simple words, the systems which control the motion of the electrical machines, are known as electrical drives. A typical drive system is assembled with a electric motor (may be several) and a sophisticated control system that controls the rotation of the motor shaft. Now days, this control can be done easily with the help of software. So, the controlling becomes more and more accurate and this concept of drive also provides the ease of use. This drive system is widel