ENGINEERING ARTICLES

A structural design project may be divided into three phases, i.e. planning, design and construction.  Planning: This phase involves consideration of the various requirements and factors affecting the general layout and dimensions of the structure and results in the choice of one or perhaps several alternative types of structure, which offer the best general solution. The primary consideration is the function of the structure. Secondary considerations such as aesthetics, sociology, law, economics and the environment may also be taken into account. In addition there are structural and constructional requirements and limitations, which may affect the type of structure to be designed.  Design: This phase involves a detailed consideration of the alternative solutions defined in the planning phase and results in the determination of the most suitable proportions, dimensions and details of the structural elements and connections for constructing each alternative structural...

The Hipot Test (Dielectric Voltage Withstand) The Hipot test is the most common type of safety test. This test is designed to stress a product’s insulation beyond what it would encounter during normal use. The reasoning behind this test is that if the insulation can withstand high voltage for short period of time, it will be safe to use at nominal voltage throughout its useful life. One of the main advantages of the Hipot test is its versatility. In addition to measuring leakage currents and detecting breakdowns, you can also use it to detect:  Material and workmanship defects.  Weak points in the insulation.  Small gap spacing between conductors. Air is just an insulator and Hipot voltage will “jump” through the air across gaps that are too small.  Condensation, dirt and contaminants in the insulation. When running a Hipot test, high voltage is applied to the mains conductors (LINE and NEUTRAL). The Hipot return point is connected to the bare metal...

There are several types of the electronic circuitry used within battery chargers for the marine market. FERRO-RESONANT (or CVT) These use a low-frequency MAGNETIC control system, which makes them very HEAVY, very BULKY and is also only available with a poor FLOAT charge characteristic, therefore very SLOW recharging. They can also generate a large magnetic field which can upset other equipment on board. On the plus side, they are CHEAP and RELIABLE due to the low number of components used and they tend to appeal to boat-builders who put the price at the top of their list of priorities.  LINEAR CHARGERS These also use a low-frequency transformer to reduce the input voltage to a lower level but then use transistors to control the current and voltage fed to the battery. This technique can be used for either FLOAT or 3-STAGE chargers but is very IN-EFFICIENT and therefore HOT, HEAVY and BULKY. The biggest drawback is a LIMITED INPUT VOLTAGE range - not ideal for running from a...

The LC and RC oscillators have their own limitations. The major problem in such circuits is that their operating frequency does not remain strictly constant. There are two principal reasons for it viz.,  As the circuit operates, it will warm up. Consequently, the values of resistors and inductors, which are the frequency determining factors in these circuits, will change with temperature. This causes the change in frequency of the oscillator.  If any component in the feedback network is changed, it will shift the operating frequency of the oscillator.  However, in many applications, it is desirable and necessary to maintain the frequency constant with extreme low tolerances. For example, the frequency tolerance for a broadcasting station should not exceed 0.002% i.e. change in frequency due to any reason should not be more than 0.002% of the specified frequency. The broadcasting stations have frequencies which are quite close to each other. In fact, the fr...

An electronic device that generates sinusoidal oscillations of desired frequency is known as a sinusoidal oscillator. Oscillator does not create energy, but merely acts as an energy converter. It receives DC energy and changes it into AC energy of desired frequency. The frequency of oscillations depends upon the constants of the device. Although an alternator produces sinusoidal oscillations of 50Hz, it cannot be called an oscillator. Firstly, an alternator is a mechanical device having rotating parts whereas an oscillator is a non-rotating electronic device. Secondly, an alternator converts mechanical energy into AC energy while an oscillator converts DC energy into AC energy. Thirdly, an alternator cannot produce high frequency oscillations whereas an oscillator can produce oscillations ranging from a few Hz to several MHz.  Advantages Although oscillations can be produced by mechanical devices (e.g. alternators), but electronic oscillators have the following advantage...

A weld joint refers to how the parts to be joined are assembled prior to welding. There are five basic types of joints used in welding which are Butt, Lap, Corner, T & Edge.  The metal to be joined is called the base metal. If the part to be welded is not metal, it is called base material. It is also known as work piece or work. The edge of base metal are often machined, sheared, gouged, flame cut, or bent to prepare them for welding. Weld joint design and metal thickness usually determine how the joint is prepared. Generally, the weld joint design is determined by an engineer. BUTT JOINT  Joins two members that meet at their edges on the same plane  Used in applications where a smooth weld face is required  Fillet or groove welded; groove welding requires added expertise and expense  Improper design/welding risks distortion and residual stresses T-JOINT Joins two members that meet at a T-shaped angle  Good mechanical properties, esp...

Steel lattice towers are also used in electronic and communication industries for communication of microwave signals through different types of antennas. Several antennae are fixed on the tower in different directions at different heights as per the requirement and usage. The antenna positions decide the height of the tower. Symmetrical cross sections are preferred for microwave towers due to reversal of wind direction. Generally steel lattice towers with square or triangular plan are used for microwave towers. Angle sections and tubes are commonly used for the fabrication of these towers. Microwave towers are generally self-supporting steel lattice towers. Guyed towers are also used for microwave communication, but are least preferred for supporting heavy disc antennae. Wind load on the tower body and antennae is the major load on the structure besides the self-weight of the tower. Microwave towers are generally supported either at ground or at rooftop of some buildings. The tip de...