Thursday, October 12, 2017

Sziklai Pair Seminar Report

Being known by a variety of names the Sziklai pair may also be known as the complementary feedback pair (CFP) or "compound transistor", and as a "pseudo-Darlington". The Sziklai pair is a configuration of two bipolar transistors, similar to a Darlington pair. In contrast to the Darlington arrangement, the Sziklai pair has one NPN and one PNP transistor, and so it is sometimes also called the "complementary Darlington". The configuration is named for its early popularizer, George C. Sziklai.

What is a Sziklai?

In essence, a high gain super transistor, somewhat similar to a Darlington. But there are major differences. Unlike Darlingtons, there is some voltage gain with Sziklais. Another unique feature is local feedback.

Why is it not as popular as EF?

Basically, more difficult to design then EF. When local feedback is nested in a global feedback, an amplifier is more prone to instability. In other words, it is easier to break out into high-frequency oscillations. But a well designed Sziklai Output can often be outstanding.

Characteristics of Sziklai Pair 

Sziklai pair seminar report
Sziklai Pair Configuration (NPN)
The current gain of the pair is similar to that of a Darlington pair and is the product of the current gains of the two transistors. The figure above illustrates an NPN-PNP pair that acts like a single NPN transistor overall. By replacing Q1 with a PNP transistor and Q2 with an NPN transistor the pair will act like a PNP transistor overall. (Just exchange the two arrows in the figure to visualize the PNP-NPN pair.)
Sziklai Pair seminar report
Sziklai Pair Configuration (PNP)
Like the Darlington, it is wise to include a bypass resistor.
Sziklai Pair seminar report
Sziklai Pair with Bypass Resistor

Sziklai compound pair features

Although the Darlington is used in many applications, the Sziklai or compound pair has a number of advantages and can be used to good effect in a number of applications. Some of its features include:

  • Only a single base emitter drop between the overall base and emitter of the compound transistor.
  • Higher saturation voltage than a Darlington.
  • Very slightly lower gain than a Darlington
  • Can be used in a pseudo-complementary output with a Darlington - a true complementary pair would use both of the same circuit configurations. This configuration, which uses three NPN transistors and one PNP transistor. It offers a number of advantages including:
    • Previously silicon PNP transistors have been more costly than their NPN equivalents because of processing techniques and also the volume usage, especially for the power transistor versions.
    • The performance of the lower "pull" pair, which uses a single NPN transistor, more closely matches the performance of the upper push pair, which consists of two NPN transistors (PNP transistors have lower carrier mobility). A true complementary pair would use all NPN for the lower pair and all PNP for the upper pair.
  • As many PNP transistors with almost equivalent performance to their NPN counterparts are now available, the advantages of using the Sziklai / compound pair are less than they used to be.
  • The Sziklai pair is known to provide a better level of linearity than the Darlington pair which can be advantageous especially in audio applications.

Applications

In a typical application, the Sziklai pair acts somewhat like a single transistor with the same type (e.g. NPN) as Q1 and with a very high current gain (β). The emitter of Q2 acts the role of a collector. Hence the emitter of Q2 is labelled "C" in the figure to the right. Likewise, in a typical application, the collector of Q2 (also connected to the emitter of Q1) plays the role of an emitter and is thus labelled "E." As with a Darlington pair, a resistor (e.g., 100Ω–1kΩ) is usually connected between Q2's emitter and base to improve its turn-off time (i.e., its performance for high-frequency signals).

Advantages

One advantage over the Darlington pair is that the base turn-on voltage is only about 0.6V or half of the Darlington's 1.2V nominal turn-on voltage. Like the Darlington, it can saturate only to 0.6V, which is a drawback for high-power stages.

Sziklai-based output stages

Sziklai pairs are often used in the output stages of power amplifiers due to their advantages both in linearity and bandwidth when compared with more common Darlington emitter follower output stages. They are especially advantageous in amplifiers where the intended load does not require the use of parallel devices.
Sziklai pairs can also have the benefit of superior thermal stability under the right conditions. In contrast to the traditional Darlington configuration, quiescent current is much more stable with respect to changes in the temperature of the higher power output transistors vs the lower power drivers. This means that a Sziklai output stage in a class AB amplifier requires only that the bias servo transistor or diodes be thermally matched to the lower power driver transistors; they need not (and should not) be placed on the main heatsink. This potentially simplifies the design and implementation of a stable class AB amplifier, reducing the need for emitter resistors, significantly reducing the number of components which must be in thermal contact with the heatsink and reducing the likelihood of thermal runaway.
Optimal quiescent current in an amplifier using Sziklai pairs also tends to be much lower than in Darlington-based output stages, on the order of 10mA vs. 100mA or more for some emitter follower output stages. This means that idle power consumption is on the order of a few watts versus tens of watts for the same performance in many cases. This is a very compelling reason to use the Sziklai pair in cases where output power is moderate (25-100W), fidelity is critical and relatively low idle power consumption is desired.

Quasi-complementary output stages

Historically, designers frequently used the "quasi-complementary" configuration, which uses a Darlington push pair (i.e., two NPN transistors) and a Sziklai pull pair (i.e., one PNP and one NPN transistor). This configuration, which uses three NPN transistors and one PNP transistor, is advantageous because while the first transistors and the most common small signal transistors for decades were PNP Germanium devices, silicon PNP power transistors were slower to develop than and have historically been more expensive than their NPN counterparts. Alternately, if a germanium PNP device were used, it would have significantly different characteristics. In the Quasi-complementary topology, the performance of the lower pull pair, which used a single NPN transistor, more closely matched the performance of the upper push pair, which consists of two NPN transistors and an identical power device.
While for decades the Quasi-complimentary output stage made sense, recently PNP and NPN power transistors have become roughly equally available and have more closely matched performance characteristics, and so modern audio power amplifiers often use equivalent topologies for both pairs, either both Darlington emitter follower or both Sziklai pair.

Sziklai compound pair gain

Although the gain of the Sziklai pair or compound pair is very nearly the same as that of the Darlington, it is not quite the same. The gain of the Darlington is given by the formula below:
The gain of the Sziklai pair is slightly different as there is no individual contribution from Q2 as seen below.

In view of the fact that the terms βQi and βQ2 on their own can be neglected, we obtain the more familiar equation which can be used for both the Darlington and Sziklai pairs.

In view of its characteristics, the Sziklai pair or compound pair finds uses in circuits in a number of areas including audio amplifier outputs, general audio amplifiers and also for digital switching.

These are some information about Sziklai Pair to make a seminar report. Kindly search the web for more information about Sziklai Pair. 


Saturday, July 15, 2017

Pneumatic Control System Seminar Report PPT

Pneumatic Control System Seminar Report: Abstract 

Control system utilize pressure differential created by gas source to drive the transfer of material. Pneumatic  control system  are all about using compressed  air to operate and power  a system  air taken from the atmosphere and squeezed are compressed .This compressed air is then used a pneumatic system  to do work . Pneumatic system are used in Meany field such as lorry brake, bicycle tires, car tires, paint spraying aircraft and hydraulic system In this paper, we propose an intelligent control method for a pneumatic servo nonlinear system with static friction. The real machine experiment confirmed the improvement of the speed of response and the stop accuracy and the effectiveness of the proposed method.
Pneumatic Control System Seminar Report PPT

Pneumatic Control System Seminar Report: Contents

1. Abstract
2. Introduction
3. Pneumatic Power Generation And Control
4. Pneumatic Uses
5. Pneumatic System Design
6. Rules Of Pneumatic Design
7. Pneumatics Components
8. Elements Of A Basic Pneumatic System
9. Advantages
10. Disvantage
11. Conculsion

Pneumatic Control System Seminar Report: Conclusion

Pneumatic controls are not well-suited for remote monitoring of space conditions and mechanical equipment status. However, at a given piece of equipment or mechanical room, pneumatic controls can provide complete and accurate information on control and equipment parameters such as temperatures and actuator positions. In most cases, this information is already available, and it requires only the addition of appropriate pneumatic indicators to display the data for the operator. The main substitute for automated remote monitoring is human monitoring. During times when the building spaces are occupied, people can report on mechanical system malfunctions or desired adjustments. For unoccupied times, basic mechanical pneumatics such as electrical service, pneumatic air pressure, critical temperatures, etc. could be monitored by a simple, low-cost, standalone electronic system.

Wednesday, June 21, 2017

ThermoAcoustic Refrigeration PPT Seminar Report

Thermoacoustic Refrigeration PPT Seminar Report : Introduction

Thermoacoustic have been known for over years but the use of this phenomenon to develop engines and pumps is fairly recent. Thermoacoustic refrigeration is one such phenomenon that uses high intensity sound waves in a pressurized gas tube to pump heat from one place to other to produce refrigeration effect. In this type of refrigeration all sorts of conventional refrigerants are eliminated and sound waves take their place. All we need is a loud speaker and an acoustically insulated tube. Also this system completely eliminates the need for lubricants and results in 40% less energy consumption. Thermoacoustic heat engines have the advantage of operating with inert gases and with little or no moving parts, making them highly efficient ideal candidate for environmentally-safe refrigeration with almost zero maintenance cost. Now we will look into a thermoacoustic refrigerator, its principle and functions.
ThermoAcoustic Refrigeration PPT Full Seminar Report

Thermoacoustic Refrigeration PPT Seminar Report: Basic Working Principle

In a nutshell, a thermoacoustic engine converts heat from a high-temperature source into acoustic power while rejecting waste heat to a low temperature sink. A thermoacoustic refrigerator does the opposite, using acoustic power to pump heat from a cool source to a hot sink. These devices perform best when they employ noble gases as their thermodynamic working fluids. Unlike the chemicals used in refrigeration over the years, such gases are both nontoxic and environmentally benign. Another appealing feature of thermoacoustics is that one can easily flange an engine onto a refrigerator, creating a heat powered cooler with no moving parts at all.
The principle can be imagined as a loud speaker creating high amplitude sound waves that can compress refrigerant allowing heat absorption. The researches have exploited the fact that sound waves travel by compressing and expanding the gas they are generated in.

Thermoacoustic Refrigeration PPT Seminar Report: Conclusion

Thermoacoustic engines and refrigerators were already being considered a few years ago for specialized applications, where their simplicity, lack of lubrication and sliding seals, and their use of environmentally harmless working fluids were adequate compensation for their lower efficiencies. This latest breakthrough, coupled with other developments in the design of high power, single frequency loud speakers and reciprocating electric generators suggests that thermo acoustics may soon emerge as an environmentally attractive way to power hybrid electric vehicles, capture solar energy, refrigerate food, air condition buildings, liquefy industrial gases and serve in other capacities that are yet to be imagined.

Saturday, June 17, 2017

Axial-Field Electrical Machines PPT-Seminar Report

Here we have uploaded the Axial-Field Electrical Machines Seminar Report.We have discussed the configuration,Advantages and the various application of Axial-Field Electrical Machines in the seminar report. If you want to download the Axial-Field Electrical Machines Seminar Report kindly find the link at the bottom of the article.We have also uploaded the Axial-Field Electrical Machines PPT with various diagram.You can download Axial-Field Electrical Machines PPT by clicking the link below.
Axial-Field Electrical Machines were soon replaced by radial-field machines (Chan). These radial-field machines have been and are still used to a large extent. One example of a popular axial-field machine is the printed circuit servomotor. As mentioned above, one drawback of the axial-field design is the strong magnetic force between its stator and rotor. This problem may be alleviated by using a sandwich configuration with a stator placed between two rotors or a rotor sandwiched between two stators.
Axial-Field Electrical Machines PPT-Seminar Report

A study of axial-field machines reveals that high electrical power to weight ratios have been achieved as shown by the works. There is reason to believe that axial-field machines will be used in the future in a large number of applications where their special features offer distinct advantages. Some potential applications of the axial-field machines include car heater blower, radiator cooling fan, auxiliary power unit, wind-power generator, electric vehicle, high speed generator driven by a gas turbine, adjustable-speed pump drive, lawnmower motor, and others.
Axial-field machines offer an alternative to the conventional radial-field machines. Their main advantages over the conventional machines are:
• They can be designed (using permanent magnets) to possess a higher power-to-weight ratio.
• They have a larger diameter-to-length ratio.
• They have a planar and adjustable air gap.
• Their magnetic circuit topology can be easily varied so that many different types of axial field machines may be designed.
Axial-field electromagnetic differential induction motors are a promising solution for electrical cars because they can behave in the same way as an electro-magnetic differential supplied by a single set of inverters. The machines can have both higher efficiency and power density compared with two individual motors. Disc-type electrical machines with permanent-magnet excitation appear to be the best design in terms of compactness, suitability in shape, robustness, and superior electrical characteristics. Because the axial-field machines can be designed to possess high power to weight ratio, they are more suitable for use in aircrafts. Their relatively flat shape makes them also suitable for ceiling-fan motors, radiator cooling fans, etc…The possibility of using an ironless rotor in the axial-field machine makes it appropriate for applications with fast response and low inertia. Moreover, the prospect of separating the stator and the rotor makes the axial-field machine design suitable for sealed and screened machines, such as domestic pump motors and wheel-directly-coupled motors for electric vehicles. Finally, reductions in the cost of high-field permanent magnets are expected to open-up several applications for the axial-field machines.



Friday, June 16, 2017

“The Ghost” Revolutionary high speed stealth attack boat for the US military and Navy

The GHOST is a super-stealth warship that is invisible for the hostile radars. The craft was built by Juliet Marine Systems. Gregory Sancoff, the CEO of Juliet Marine Systems Inc. spent a decade designing and building this thing. The 60-foot long GHOST is shown bristling with weapons in slickly produced Juliet videos while its stealthy silhouette slices effortlessly and ominously through the water. It surpasses 50 knots (57 mph) by surrounding each ski with a bubble of air that helps it cut through water much easier than regular boats. It's a concept called super-cavitation. Ghost is powered by two jet engines, and uses a gyro-stabilized dual-pontoon supercavitating hull to run at top speed through 10-ft seas.
This fast attack stealth boat will make a difference. GHOST is a super-cavitating surface craft which is able to achieve 900 times less hull friction compared to a conventional watercraft and is developed by US Citizens for the US Navy at no cost to the US government for providing superior protection to US service personnel. GHOST is designed for fleet protection for navies with few blue-water needs but require a small and affordable craft in large numbers for near-shore maritime border patrol and defense missions; it is being offered to international customers including Bahrain, Qatar, Israel, Saudi Arabia, Japan, Taiwan, South Korea, and Singapore. While the GHOST is a surface vessel, the hydrodynamics of the twin submerged buoyant tubular foils are also a test bed for Juliet Marine's next planned prototype, a long duration UUV. The GHOST is a revolutionary proprietary technology vessel platform that will assure force protection through stealth fighter/attack capabilities along with integrated situation awareness.