Electronic Ballasts
Instant-start electronic ballasts are the most popular type of electronic ballast today because they provide maximum energy savings and they start lamps without delay or flashing. Since they do not provide lamp electrode heating, instant-start ballasts generally consume less energy than comparable rapid-start,
program rapid-start or programmed-start ballasts. As a result, they usually provide the most energy efficient solution to fluorescent lamp ballasting. The instant-start ballast uses 1.5 to 2 watts less energy per lamp than the rapid-start alternative. The also have the least amount of output leads, making for easy wiring.
Principle of Operation of DC Machines
Principle of Operation of D.C Machines [ Example of Single conductor Generator & Motor ~ Rotating Machines ~ Driving & Opposing torques ~ Generator mode ~ Motor mode ~ Condition for steady production of torque ~ D.C generator: Basic principle of operation ~ D.C motor: Basic principle of operation ]
Op Amps for Everyone
some of content:
Split-Supply Op Amp Circuit
Single-Supply Op Amp Circuit
Inverting Op Amp with Noninverting Positive Reference
Differential Amplifier
Inverting AC Amplifier
Inverting Integrator
Centrifugal Pumps: Basic Concepts of Operation, Maintenance
The operating manual of any centrifugal pump often starts with a general statement,“Your centrifugal pump will give you completely trouble free and satisfactory service only on the condition that it is installed and operated with due care and is properly maintained.”
DC Machine Armature Winding
In this lesson, important constructional features of a D.C machine are presented along with a discussion on D.C armature winding. Key Words: Field winding, armature winding, commutator segments & brush arrangement. After going through this section students will have clear ideas about the followings:
• The function of commutator & brush in a D.C Machine.
• Double layer winding.
• Coil span & commutator pitch.
• Lap & wave winding and number of armature parallel paths.
An Introduction to the Petroleum Industry
Oil, petroleum, natural gas, hydrocarbons and crude are terms we commonly hear. If we are going to study the oil industry, we must first become familiar with the “lingo”. Appendix I provides a glossary, but it will be useful at this point to introduce you to the some of the key terms.
Cathodic Protection
Cathodic protection is a system utilized to inhibit corrosion of structures, such as underground pipes, tanks, etc. Corrosion is an electrochemical process in which a current leaves a structure at the anode site, passes through an electrolyte, and reenters the structure at the cathode site. For example, because it is in a soil with low resistivity compared to the rest of the line, current would leave the pipeline at that anode site, pass through the soil, and reenter the pipeline at a cathode site. Current flows because of a potential difference between the anode and cathode. The anode potential is more negative than the cathode potential, and this difference is the driving force for the corrosion current. The total system – anode, cathode, electrolyte, and metallic connection between anode and cathode is termed a corrosion cell. For corrosion to occur, the following conditions are required.
Micro-Heat Engines,Gas Turbines and Rocket Engines
This is a report on work in progress on microelectrical and mechanical systems (MEMS)-based gas turbine engines, turbogenerators, and rocket engines currently under development at MIT. Fabricated in large numbers in parallel using semiconductor manufacturing techniques, these engines are based on micro-high speed rotating machinery with the same power density as that achieved in their more familiar, full-sized brethren. The micro-gas turbine is a 1 cm diameter by 3 mm thick SiC heat engine designed to produce 10-20 W of electric power or 0.05- 0.1 Nt of thrust while consuming under 10 grams/hr of H2. Later versions may produce up to 100 W using hydrocarbon fuels. A liquid fuel, bi-propellant rocket motor of similar size could develop over 3 lb of thrust. The rocket motor would be complete with turbopumps and control valves on the same chip. These devices may enable new concepts in propulsion, fluid control, and portable power generation.
Gas Turbines and Jet Engines
A simple-cycle gas turbine has one turbine driving one compressor and a power-consuming load. More complex configurations are discussed later. It is assumed that the compressor inlet state, the compressor pressure ratio, and the turbine inlet temperature are known, as before. The turbine inlet temperature is usually determined by the limitations of the high-temperature turbine blade material. Special metals or ceramics are usually selected for their ability to withstand both high stress at elevated temperature and erosion and corrosion caused by undesirable components of the fuel.
Let’s consider a two-shaft gas turbine with a regenerative air heater. The compressor pressure ratio is 6, and the compressor and gas generator turbine inlet temperatures are 520°R and 1860°R, respectively. The compressor, gasifier turbine, and power turbine
isentropic efficiencies are 0.86, 0.89, and 0.89, respectively. The regenerator effectiveness is 75%, and a 4% pressure loss is shared by the high-pressure air side of the regenerator and the combustor. Determine the pressure ratios of the two turbines,
and the net work, thermal efficiency, and work ratio of the engine.
Fundamentals of the Gas Turbine Engine
The gas turbine is an internal combustion engine that uses air as the working fluid.The engine extracts chemical energy from fuel and converts it to mechanical energy using the gaseous energy of the working fluid (air) to drive the engine and propeller,which, in turn, propel the airplane.
The turbine section of the gas turbine engine has the task of producing usable output shaft power to drive the propeller. In addition, it must also provide power to drive the compressor and all engine accessories. It does this by expanding the high temperature, pressure, and velocity gas and converting the gaseous energy to mechanical energy in the form of shaft power.
