211 SRI RAMAKRISHNA MISSION VIDYALYA POLYTECHNIC COLLEGE.

  Applications of DC Motors The applications of different types of DC motors are given below  Series DC Motor Series DC motors are used in applications where high starting torque is required. Series DC motors are used in cranes and hoists. Series DC motors are used in electric tractions. They are used in air compressors. They are also used in vacuum cleaners. Series DC motors are also used in sewing machines, etc. Shunt DC Motor Shunt DC motors are used in applications that require constant speed. Shunt DC motors are used for driving lathe machines. These are also used in centrifugal pumps and blowers. These are used in fans, conveyors, and spinning machines. These DC motors are also used in lifts. Compound DC Motor Compound DC motors are used in those applications which require high starting torque and constant speed. Used in printing presses. They are also used in shears. They are used in elevators and lifts. Compound DC motors are also used in rolling mills and heavy planne...

  In recent years, semiconductor packaging has evolved with an increased demand for greater functionality, smaller size, and added utility. A modern PCBA design has two main methods for mounting components onto a PCB:  Through-Hole Mounting  and  Surface Mounting.   Through-Hole Mounting (THM): Through-hole mounting is the process by which component leads are placed into drilled holes on a bare PCB. The process was standard practice until the rise of surface mount technology (SMT) in the 1980s, at which time it was expected to completely phase out through-hole. Yet, despite a severe drop in popularity over the years, through-hole technology has proven resilient in the age of SMT, offering a number of advantages and niche applications: namely, reliability.   Through-hole components are best used for high-reliability products that require stronger connections between layers. Whereas SMT components are secured only by solder on the surface of the boa...

  SPECIAL FUNCTION REGISTER (SRF) OF 8051 MICROCONTROLLER To monitors or control the various functions within a microcontroller like control different hardware peripherals like Timers, Serial Port, I/O Ports etc. Here we use some special registers in 8051 microcontroller called  Special Function Register (SRF)  (or Special Purpose Register, or simply Special Register). If we want to assess or change the operating mode of the 8051 Microcontroller. This will be done by manipulating the 8051 Microcontroller  Special Function Registers (SFRs). In 8051 micro controller there are  21 Special function registers (SFR)  and this includes Register A, Register B, Processor Status Word (PSW), PCON etc.  So, it required 21 unique locations for these 21 special function registers and the size of each register is of 1 byte. Some of these special function registers are  bit addressable   registers  (which means you can access 8 individual bits...

  What Is a Universal Motor? A universal motor is a special type of motor that runs on both AC and DC power supplies. Universal motors are series-wound (the armature and field windings are in series). The series connection allows them to generate high torque; hence the universal motors are generally built into the device they are meant to drive. Most of the universal motors are meant to operate at speeds as high as 3500 RPM. These motors run at a higher speed on DC supply than they run on AC supply of the same voltage. This is due to the reactance voltage drop that is present only in AC and not in DC. How does a Universal Motor run on both AC and DC supply? The construction of a universal motor is similar to that of a  series-wound DC motor . A universal motor incorporates some modification that allows it to operate either on AC or DC supply. Construction of a Universal Motor A universal motor consists of a stator on which the field poles are mounted. Field coils are wound aro...

  Corona Effect in Overhead Transmission Line The phenomenon of violet glow, hissing sound and production of ozone gas in an overhead transmission line is known as  corona . When a very high voltage is applied across two conductors of the overhead transmission line whose spacing is large as compared to their diameters.  When this applied voltage exceeds a certain value (called critical disruptive voltage), then the conductors are surrounded by a faint violet glow that is known as  corona effect . In practice, the corona effect is accompanied by a hissing sound, production of ozone, power loss and radio interference. The higher is the transmission voltage, the larger and higher the luminous envelope becomes and the higher are the power loss and the radio interference.  If the applied voltage attained the breakdown value, then a flashover will occur between the conductors due to breakdown of the insulation of air. If the transmission conductors are polished and sm...

  Comparison of 8051 with its other family members Introduction : 8051  is 8-bit microcontroller with 4 KB program memory and 128 Bytes data memory. Other features include four 8-bit ports, two 16-bit timers and one on-chip serial port.  Overview of the 8051 Family :  8051 microcontroller was initially designed by Intel Corporation in 1981. Features of 8051 made it extremely popular in market. Because of it’s popularity and high demand Intel allowed other manufacturers to fabricate and market different variants of 8051 with a condition that all these variants should be code compatible with 8051. This resulted in a lot of variants of 8051 in market, among which 8052 and 8031 are the most popular ones. Therefore, 8052 and 8031 are considered as the family members of 8051. 8052 –  8052 is the super set of 8051 as it has all the features of 8051 with an extra timer and an extra RAM of 128 bytes. Therefore, 8052 has a total of 256 bytes of RAM and 3 timers in all. Al...

Working of DOL Starter  The wiring connection of DOL starter with start and stop buttons is shown in figure below. The DOL starter main terminals are connected between the mains supply terminals and motor terminals while the control circuit is energized with two terminals of three phase supply as illustrated in figure When the start button is pressed, current will flow through one phase to the control circuit and the contactor coil to the other phase. This current energizes the contactor coil which makes to close the contacts thereby three phase supply is connected to the motor. Since the start button is of pushbutton, when it is released the control circuit still maintains the supply through hold-on contact. If the stop button is pressed or overload relay coil operate, the current path through contactor coil will break and hence the contactor contacts drops out, thus breaking the supply to the motor. Once the power supply is interrupted, again the supply to the motor is establishe...

  FM is short for frequency modulation, which refers to the means of encoding the audio signal on the carrier frequency. FM full power,  low power , translator and booster stations operate in the 88 – 108 MHz band. There are many classes of radio stations. The smallest provide service to areas within three or four miles of a transmitter site; the largest provide service to locations more than 60 miles from a transmitter site. Only noncommercial educational radio stations are licensed in the 88-92 MHz “reserved” band. Both commercial and noncommercial educational stations may operate in the “non-reserved” 92-108 MHz band.

  Permanent Magnet DC Motor The permanent magnet dc motor can be defined as a motor which includes a permanent magnet pole is called Permanent Magnet DC Motor.  In this motor, the magnet can be used to make the flux working within the air gap in its place of the field winding.   The rotor structure is similar to the straight DC Motor. PMDC Motor’s rotor includes armature core, commutator, &  armature winding .  Normally, in a conventional DC motor, there are two kinds of winding such as armature as well as Filed. PMDC Motor The main function of field winding is to produce the functioning magnetic flux within the air gap as well as wound on  the stator  of the motor while armature winding can be wound on the rotor. Inactive carbon brushes are pushed on the commutator like in conventional DC motor.  The operating voltage of the PMDC motor is 6 volts, 12 volts otherwise 24 volts DC supply attained from the voltage sources.

  What is a Single Phase Transformer? A single phase transformer is a type of transformer which operates on single-phase power. A transformer is a  passive electrical device  that transfers electrical energy from one circuit to another through the process of  electromagnetic induction . It is most commonly used to increase (‘step up’) or decrease (‘step down’)  voltage  levels between circuits.

 Resistors in Series and Parallel Combinations A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. Resistors reduce the current flow and lower voltage levels within circuits. Most circuits often have more than one resistor to limit the flow of charges in a circuit. The two simplest combinations of resistors are – series and parallel. In this article, we will be discussing resistors in series and parallel combinations. Circuit Components A circuit is composed of conductors (wire), power source, load, resistor, and switch. A circuit starts and ends at the same point. Usually, copper wire without insulation is used as a conductor. A switch is used to make or break a circuit. Resistors control the flow of the electric current in a circuit. A resistor is a passive element which means that it only consumes power but does not generate power. A load in a circuit consumes electrical energy and converts it into other forms of ...

  Speed Vs. Armature Current (N-Ia) As flux ɸ is assumed to be constant, we can say N ∝ Eb. But, as back emf is also almost constant, the speed should remain constant. But practically, ɸ as well as Eb decreases with increase in load. Back emf Eb decreases slightly more than ɸ, therefore, the speed decreases slightly. Generally, the speed decreases only by 5 to 15% of full load speed. Therefore,  a shunt motor can be assumed as a constant speed motor . In speed vs. armature current characteristic in the following figure, the straight horizontal line represents the ideal characteristic and the actual characteristic is shown by the dotted line.

  concentrating solar-thermal power   (CSP) technology and  CSP technologies use mirrors to reflect and concentrate   sunlight   onto a receiver.  The energy from the concentrated sunlight heats a high temperature fluid in the receiver. This heat - also known as  thermal energy  - can be used to spin a turbine or power an engine to generate electricity. It can also be used in a variety of industrial applications, like water desalination, enhanced oil recovery, food processing, chemical production, and mineral processing. Concentrating solar-thermal power systems are generally used for utility-scale projects. These utility-scale CSP plants can be configured in different ways.  Power tower systems arrange mirrors around a central tower that acts as the receiver.  Linear systems  have rows of mirrors that concentrate the sunlight onto parallel tube receivers positioned above them.  Smaller CSP systems can be lo...

DEFINITION semiconductor What is a semiconductor? A semiconductor is a substance that has specific electrical properties that enable it to serve as a foundation for computers and other electronic devices. It is typically a solid chemical element or compound that conducts electricity under certain conditions but not others. This makes it an ideal medium to control electrical  current  and everyday electrical appliances.  A substance that can conduct electricity is called the  conductor  and a substance that cannot conduct electricity is known as the insulator. Semiconductors have properties that sit between the conductor and insulator. A  diode , integrated circuit ( IC ) and  transistor  are all made from semiconductors.  The  conductance  can vary depending on the current or voltage applied to a control electrode or on the intensity of irradiation by infrared ( IR ), visible light, ultraviolet or X-rays. The specific prop...