ENGINEERING ARTICLES

Electrical power system harmonic problems are mainly due to the substantial increase of non-linear loads due to the technological advances, such as the use of power electronic circuits and devices, in ac/dc transmission links or loads in the control of power systems using power electronics or microprocessor controllers. Such equipments create load-generated harmonics throughout the system.Prior to the appearance of power semiconductors, the main sources of waveform distortion were electric arc furnaces, the accumulated effect of fluorescent lamps and to a lesser extent electrical machines and transformers. In general, harmonic sources are given below Converters,  Devices which includes semi-conductor elements,  Generators,  Motors,  Transformers,  Lightening equipment working by gas discharge principle,  Photovoltaic systems,  Computers,  Electronic ballasts,  Uninterruptable power supplies,  Switching power supplies,  ...

There are so many Technical methods for the prevention and correction of voltage sag a few of them are described below. Tap Changing Transformers Saturable Reactor Regulators Static Voltage Regulator (SVR) Motorized Variacs Phase Controlled Regulators Electronic Voltage Regulators Soft Switching Line Conditioners Ferro resonant Transformers (CVT) Magnetic Synthesizers Flywheels and Motor-Generator (M-G) Sets Uninterruptible Power Supplies (UPS); Battery Storage)  Superconducting Magnetic Energy Storage (SMES) Compressed Air Energy Storage (CAES) Dynamic Voltage Restorer (DVR) Energy storage using capacitors. Super capacitors Dynamic Sag Corrector (DySC) So these were the technical methods used inside the industrial plants to improve the power quality of the system against voltage sag, short interruptions and for their correction. If we want to study each technique, it is a wide field and for ideas about the techniques mentioned in the list you can go through refer...

Power Quality Management plays an important role in improving power quality. The fundamental goal of energy management is to produce goods and provide services with the least cost and least environmental effect. The term energy management means many things to many people The objective of Energy Management is to achieve and maintain optimum energy procurement and utilization, throughout the organization and To minimize energy costs / waste without affecting production & quality, To minimize environmental effects. The strategy of adjusting and optimizing energy, using systems and procedures so as to reduce energy requirements per unit of output while holding constant or reducing total costs of producing the output from these systems. Management always keeps an eye to the monitoring equipment to monitor currents, voltages, harmonics and power as performance values for supporting network plans and operational which support power systems availability, efficiency, reliability. The proces...

VOLTAGE IMBALANCE: Voltage imbalance is regarded as any differences in the three phase voltage magnitudes and/or shift in the phase separation of the phases from 120 degrees.It is normally expressed as the negative phase sequence divided by the positive phase sequence,as a percentage, measured using line to line voltages. EFFECTS OF VOLTAGE IMBALANCE: The effects of voltage unbalance are mainly associated with three phase motors. These effects are namely: Increased motor losses, reduced efficiency and therefore increased running costs;  Increased losses results in additional heating and loss of motor insulation life;  Effective torque and speed will be reduced;  Increased motor noise; CAUSES OF VOLTAGE IMBALANCE: The causes of voltage imbalance include:  Large and/or unequal single phase loads;  The uneven connection of single phase customers to the distribution system;  The uneven connection of single phase transformers or spur ...

The following points are the difference between Induction and Synchronous motor .

Variously called intelligent motors, smart motors or integrated motors and drives, these units combine a three-phase electric motor and a pulse width modulated inverter drive in a single package. Some designs mount the drive components in what looks like an oversize conduit box. Other designs integrate the drive into a special housing made to blend with the motor. A supplementary cooling fan is also frequently used for the drive electronics to counteract the rise in ambient temperature caused by being in close proximity to an operating motor. Some designs also encapsulate the inverter boards to guard against damage from vibration. Size constraints limit integrated drive and motor packages to the smaller horsepower ranges and require programming by remote keypad, either hand-held or panel mounted. Major advantages are compactness and elimination of additional wiring.

Direct current drives are easy to apply and technologically straight forward. They work by rectifying AC voltage from the power line to DC voltage, then feeding adjustable voltage to a DC motor. With permanent magnet. DC motors, only the armature voltage is controlled. The more voltage supplied, the faster the armature turns. With wound-field motors, voltage must be supplied to both the armature and the field. In industry, the following three types of DC drives are most common: DC SCR Drives: These are named for the silicon controlled rectifiers (also called thyristors) used to convert AC to controlled voltage DC. Inexpensive and easy to use, these drives come in a variety of enclosures, and in unidirectional or reversing styles. Regenerative SCR Drives: Also called four quadrant drives, these allow the DC motor to provide both motoring and braking torque. Power coming back from the motor during braking is regenerated back to the power line and not lost. Pulse Width Modulat...

Major maintenance, troubleshooting and repair of drives should be left to a qualified technician, following the drive manufacturer’s recommendations. However, routine maintenance can help prevent problems. Here are some tips: • Periodically check the drive for loose connections or any other unusual physical conditions such as corrosion. • Vacuum or brush heat sink areas regularly. • If the drive’s enclosure is NEMA 1, be sure vent slots are clear of dust or debris. • If the drive is mounted within a secondary enclosure, again be sure vent openings area clear and that any ventilation fans are operating properly. • Unless it is otherwise necessary for major maintenance or repair, the drive enclosure should not be opened.

As PWM AC drives have continued to increase in popularity, drives manufacturers have spent considerable research and development effort to build in programmable acceleration and deceleration ramps, a variety of speed presets, diagnostic abilities, and other software features. Operator interfaces have also been improved with some drives incorporating “plain- English” readouts to aid set-up and operation. Plus, an array of input and output connections, plug-in programming modules, and off-line programming tools allow multiple drive set-ups to be installed and maintained in a fraction of the time spent previously. All these features have simplified drive applications. However, several basic points must be considered: Torque: This is the most critical application factor. All torque requirements must be assessed, including starting, running, accelerating and decelerating and, if required, holding torque. These values will help determine what current capacity the drive must have in order f...

One drawback to pulse width modulated drives is their tendency to produce voltage spikes, which in some instances can damage the insulation systems used in electric motors. This tendency is increased in applications with long cable distances (more than 50 feet) between the motor and drive and with higher-voltage drives. In the worst cases, the spikes can literally “poke a hole” into the insulation, particularly that used in the motor’s windings. To guard against insulation damage, some manufacturers now offer inverter-duty motors having special insulation systems that resist voltage spike damage. For example, LEESON’s system, used in all three-phase motors 1 HP and larger, is called IRIS™ (Inverter Rated Insulation System). Particularly with larger drives, it may be advisable to install line reactors between the motor and drive to choke off the voltage spikes. In addition, some increased motor heating will inevitably occur because of the inverter’s “synthesized” AC wave form. Insulatio...

By definition, adjustable speed drives of any type provide a means of variably changing speed to better match operating requirements. Such drives are available in mechanical, fluid and electrical types. The most common mechanical versions use combinations of belts and sheaves, or chains and sprockets, to adjust speed in set, selectable ratios – 2:1, 4:1, 8:1 and so forth. Traction drives, a more sophisticated mechanical control scheme, allow incremental speed adjustments. Here, output speed is varied by changing the contact points between metallic disks, or between balls and cones. Adjustable speed fluid drives provide smooth, step less adjustable speed control. There are three major types. Hydrostatic drives use electric motors or internal combustion engines as prime movers in combination with hydraulic pumps, which in turn drive hydraulic motors. Hydrokinetic and hydro viscous drives directly couple input and output shafts. Hydrokinetic versions adjust speed by varying the amount of ...

When a current-carrying conductor is placed in a magnetic Field, it experiences a force. Experiment shows that the magnitude of the force depends directly on the current in the wire, and the strength of the magnetic Field, and that the force is greatest when the magnetic Field is perpendicular to the conductor. In the set-up shown in Figure 1.1, the source of the magnetic field is a bar magnet, which produces a magnetic Field as shown in Figure 1.2. Figure 1.1 Mechanical force produced on a current-carrying wire in a magnetic Weld The notion of a ‘magnetic Field’ surrounding a magnet is an abstract idea that helps us to come to grips with the mysterious phenomenon of magnetism: it not only provides us with a convenient pictorial way of picturing the directional eVects, but it also allows us to quantify the ‘strength’ of the magnetism and hence permits us to predict the various eVects produced by it. The dotted lines in Figure 1.2 are referred to as magnetic Flux lines, or simp...

Actuators are operated in the same way as solenoids. They are used to move mechanisms remotely. Some examples of actuators on a vehicle are, door locks, pre-engaged starter motors and fuel cut off valves. Consider the diagram below. Like a solenoid or relay an actuator has a winding. When current flows around the winding, the winding is energized. Two types of actuator are used, a short rated version and a continuously rated version. The short rated actuator is used for simple on/off operation. This type of actuator has one winding which cannot be operated for longer than 15 seconds. An example where this type of actuator could be used would be a door lock. The continuously rated actuator has two windings. The first winding is used to pull the actuator arm into the winding, the second is used to hold the actuator arm in the winding. The pull in winding may require a current of as much as 35 amps. The hold in winding may only require a current of 4 amps. The continuously ra...

A solenoid is the term used for a heavy duty relay and like a relay acts as a switch saver. Solenoids are used to switch circuits that require a very large current to operate. An example of this type of circuit is the starter circuit.  Consider the diagram below. Since the starter circuit requires a lot of current to operate, the diagram above would be impractical. This is because the contacts of the ignition switch would need to be very large to carry the large current. Also the large cables required to carry the current would need to be very long. By using a solenoid, small ignition switch contacts can be used and the length of cable can often be reduced. This will reduce the voltage drop in the circuit. Voltage drop is the term used to describe a reduction of voltage between two points. e.g. between the ignition switch and the starter solenoid. Voltage drop is proportional to resistance. Long cables, small diameter cables and corroded connections all cause an increase in ...

This is sometimes known as an ‘either/or’ relay because you can use either one circuit or the other. This type of relay is particularly useful for headlights. Pin number 87A feeds the dipped beam circuit. When the driver selects main beam the relay is energised so the moving contact moves to pin 87 and feeds the main beam circuit. So with the five pin relay you can have either dipped beam or main beam. The basic relay works in three stages. Stage 1: When the switch (A) is closed, current flows through the winding around the soft iron core and down to earth at (B).This action magnetises the iron core. Stage 2: The magnetised iron core attracts the metal moving contact (C) which touches the fixed contact (D). Current can now flow from supply 2through the contacts and on to the load (E) e.g. a heated rear window. Stage 3: When the switch (A) is opened the current stops flowing around the iron core, so the magnetic field collapses. The moving contact is then pulled...

Relays are used extensively in modern vehicles. They can be thought as electro/mechanical switches. They are often used to switch on circuits that require a heavy current e.g. the heated rear windscreen (H.R.W.) circuit. If a relay was not used the contacts inside the HRW switch would need to be quite large to carry the heavy current. By using a relay, smaller switch contacts can be used. The relay then acts as a switch saver. Relays can be used to avoid voltage drop and reduce the amount of heavy duty cable required. They can also ensure that contacts make and break cleanly. Relays also make a convenient point for testing individual circuits. From the circuit diagrams with circuit A the HRW switch has to carry the full current. However, with circuit B the HRW switch only needs to carry enough current to activate the relay. When the relay is activated it closes the relay switch. The feed for the HRW then comes through the 16 amp fuse and the contacts of the relay. By taking this route ...

When the armature rotates a half a revolution ‘A’ is positioned at the south pole “S” and ‘B’ positioned at the north pole “N”. As the magnetic field surrounding ‘A’ is in the anti-clockwise direction the magnetic field would be stronger under ‘A’ and above ‘B’, which would mean that the armature would now rotate in the opposite direction. The motor would never rotate. To maintain rotation of the armature in the one direction the flow or current through the armature must be reversed when ‘A’ is at the “S” pole of the field coil. A commutator is used with the motor to reverse the current flowing in the armature. Fig. “X” shows the black half of the armature at “N” and is connected via the segment of the commutator through the carbon brush to the battery negative terminal. In this position, the current flow through the armature produces a magnetic field of anti-clockwise direction through the black half ‘A’ of the armature and clock-wise through the white ‘B’. Interaction occurs and the...

To understand this rule, open your hand, as shown below, with the thumb pointing perpendicular to the index finger, and the index finger perpendicular to the middle finger. Then, point the index finger in the direction of the magnetic flux, and the middle finger in the direction of the current. The direction in which the thumb points will then be the direction of the electromagnetic force, and therefore, the direction in which the conductor moves.

An electromagnetic force is a force that acts on a conductor when current flows in the conductor within a magnetic field. It is utilised to operate starter and wiper motors, and the pointers of ammeters, voltmeters, etc. DIRECTION OF ELECTROMAGNETIC FORCE Let’s assume the N and S poles of a magnet are placed near other, and a conductor is put between them, as shown. Then current is applied to the conductor. The following can be said about the magnetic flux created in this case: There are a smaller number of magnetic lines of force above the conductor since the direction of the magnetic fluxes created by the magnet and the direction of those created by current oppose each other. In contrast, there are a larger number of magnetic lines of force under the conductor as their directions coincide. Since magnetic lines of force act similarly to stretched rubber bands in many ways, the magnetic lines of force attempt to become straight. This tendency is stronger under the conducto...

TESTS WHEN ISOLATED 1) VISUAL TESTS: Check that motor frame is mechanically sound.  Remove terminal cover plate and check for ingress of foreign material, moisture etc.  Check for signs of overheating, arcing or burning.  Check ventilation is clear.  2) ELECTRICAL TESTS: Identify windings using a continuity tester.  Measure the resistance of the windings ( 3 identical readings ).  Measure the insulation resistance between each winding and between windings and frame.  3) MECHANICAL TESTS: Check that the rotor is free to rotate and does so smoothly / quietly. Check that motor interior is free of dirt, dust, water and oil. Check for play in bearings. 4) TESTS WHEN RUNNING: Check run currents ( If uneven check voltage at motor terminals ).  Check speed of motor at no load and full load.  Check vibration levels and noise levels.  Check for temperature hot spots.

Electric motors and generators are referred to as electric machines. Electricians are most frequently concerned with electric motors, due to their extensive application. The electric motor must be one of man’s most useful inventions. In the manufacturing industries they are used in large numbers, to drive lathes, drilling and milling machines, augers, conveyors, cranes, hoists, lifts, fans and steel rolling equipment. In the process industries they are used to pump liquids and gases. They are used in transport to start engines, operate windscreen wipers, open and close windows and power electric vehicles. In domestic situations they are used in washing machines, clothes dryers, cookers, fridges, freezers, vacuum cleaners, food mixers, audio / video equipment, cameras, clocks etc. Electric motors are popular because they are compact, reliable, and cheap, need little attention, and are convenient to use. They can be provided in a wide range of sizes and can be designed to have...

SR motors do not contain magnets and are constructed such that both the stator and rotor have salient poles. The motor is driven by a sequence of current pulses applied at each phase, which requires control electronics for operation. The SR motor works on the principle that the magnetic circuit tries to minimize the reluctance (air gap distance) of the magnetic circuit. The magnetic field creates a force on the rotor so that its poles line up with the poles of stator phase. ADVANTAGES OF SWITCHED RELUCTANCE MOTOR: • Low cost resulting from simple construction. • High reliability. • High fault tolerance. • Heat generated in stator is easy to remove. • High-speed operation possible. DRAWBACKS OF SWITCHED RELUCTANCE MOTOR: • Acoustically noisy. • High vibration. • Magnetic non-linearities make smooth torque control difficult. • Dependent on electronic control for operation.

ACIM is the most popular motor for industrial and consumer applications. This is due to many factors such as the lack of commutator/brushes (high reliability), high efficiency at high loads and the ability to connect directly to the AC line. ACIMs have a classic three-phase stator and commonly have a “squirrel cage” rotor in which the conductors are shorted together at both ends. The operation principle of ACIM is very similar to a transformer. A rotor current is induced in the rotor circuit from the stator windings. This current produces rotor flux, which interacts with the stator electromagnets to produce torque. ADVANTAGES OF AC INDUCTION MOTOR • Low cost per horsepower (no permanent magnets). • Inherent AC operation (direct connection to AC line). • Very low maintenance (no brushes) and rugged construction. • Available in wide range of power ratings. • Low-cost speed control with tachogenerator. • Simple control (volt per hertz + PFC can handle 8-bit MCU ). DRAWBACKS OF AC ...

Similar to BLDC motors, PMSMs have a three-phase stator and a rotor with surface/interior-mounted permanent magnets. A PMSM provides rotation at a fixed speed in synchronization with the frequency of the power source. PMSMs are therefore ideal for high-accuracy fixed-speed drives. Boasting very highpower density, very high efficiency and high response, the motor is suitable for most sophisticated applications in the industrial segment. It also has a high overload capability. A PMSM is largely maintenance free, which ensures the most efficient operation. Synchronous motors operate at an improved power factor, thereby improving the overall system power factor and eliminating or reducing utility power factor penalties. An improved power factor also reduces the system’s voltage drop and the voltage drop at the motor terminals. ADVANTAGES OF PERMANENT MAGNET SYNCHRONOUS MOTOR: • Heat generated in stator is easy to remove. • High torque per frame size. • Reliability due to absence of...

BLDC motors have a three-phase stator winding and a rotor with surface-mounted permanent magnets. A BLDC motor does not have a commutator and is more reliable than a DC motor. The digital control and power electronics replace the function of the commutator and energize the proper winding. They are used in home appliances (such as refrigerators, washing machines and dishwashers), pumps, fans and other devices that require high reliability and efficiency. In the BLDC motor, the rotor position must be known to energize the phase pair and control the phase voltage. If sensors are used to detect rotor position, then sensed information must be transferred to a control unit. This requires additional connections to the motor, which may not be acceptable in some applications. Also, the additional cost of the position sensors and the wiring may be unacceptable. The physical connection problem could be solved by incorporating the driver in the motor body, however, a significant number o...

Digital control allows more efficient motor control with variable speed and sensor-less control. The term sensor-less control means that there is no position/ velocity sensor on the motor shaft, so the rotor position/velocity is calculated from measured current and voltage. The sensor-less control provides a cost-effective and reliable solution that eliminates the position/velocity sensor, sensor wiring, sensor power supply and increases reliability. Still, there are applications where higher cost of sensors is not as important as higher position resolution. The most common speed/position sensors are: • Tachogenerators • Hall sensors • Encoders • Re-solvers Applications requiring the motor to operate with a required speed (pumps, fans, compressors, etc.) are speed controlled. In variable frequency drives, motor speed is typically proportional to frequency. The actual motor speed is maintained by a speed controller to reference speed command. Speed control offers low dynamic performance...

• Minimize energy losses • Prevent environment pollution • Decrease acoustic noise and power harmonics • Increase system performanceversus- cost ratio • Increase productivity, flexibility and robustness • Increase safety and reliability • Reduce system size and weight • Growth of digital control and reducing usage of analog components and total system cost. Motor types that most effectively meet these requirements include AC induction motors (ACIM), permanent magnet synchronous motors (PMSM), brushless DC motors (BLDC) and switched reluctance motors (SR).

According to IEC 60034-5, the motor will be weather protected when due to its design ( technical discussion between customer and WEG ), the defined protections provide a correct operation of the motor against rain, dust and snow. WEG also uses the letter W to indicate the degree of protection of the motor to indicate that the motor has a special paint plan ( weather protected ). The painting plans may vary according to the environmental severity, which should be informed by the customer during motor specification/order. Aggressive environments require that equipment be perfectly suitable to support such conditions ensuring high reliability in service without showing any problems. WEG manufacturers a wide range of electric motors with special characteristics, suitable for use in shipyards, ports, fishing plants and several naval applications, as well as in chemical and petrochemical industries and other aggressive environments. So WEG motors are suitable to operate under the most severe...

Service factor is the factor that, when applied to rated output, represents the allowable load that can be applied to motor continuously, under specified operating conditions. Note that this refers to continuous overload conditions, i.e., a power reserve that gives the motor a better capacity to withstand adverse operating conditions. Service factor should not be confused with momentary overload capacity during few minutes. A service factor = 1.0 means that the motor has not been designed for continuous operation above its rated output. However, this does not change its capacity to withstand instantaneous overloads. NBR 17094 specifies the most common Service Factors per motor output.

The brake motor consists of an induction motor coupled to a single-disc brake, forming an integral, compact unit. The induction motor is a totally enclosed fan cooled machine with the same mechanical and electrical performance of WEG general purpose motors. The brake is built with few movable parts which gives long life with reduced maintenance. The two faces of the brake pads create a large contact area, requiring only little pressure during the braking process, which reduces the brake heating and the wear is minimum. Besides that, brake is cooled by the motor cooling system. The electromagnet drive coil, protected with epoxy resin, can be operated continuously with voltages varying 10% above and below the rated voltage. The electromagnet drive coil is DC powered, supplied by a bridge rectifier made of silicon diodes and varistors, that suppress undesirable voltage spikes and allow a fast current shutdown. The DC power supply provides faster and smoother brake operation. TYPICAL APPL...

Although WEG states that their motors usually comply with Design N, in many cases their typical actual torque values far exceed the minimum required by the standard. In most cases the values even exceed the minimum requirements of Design H. This means a very high speed-torque curve, bringing the following benefits: 1 ) Quick acceleration under heavy starting conditions, e.g. for piston pumps, loaded conveyers, high inertia loads, compressors with open valves, etc. 2 ) Quick responsiveness for special supplies such as those mentioned since standard motors are always readily available from stock, with price benefits and quick delivery. 3 ) The possibility of using reduced voltage starting methods, e.g. Star-Delta Starters, in normal cases, without affecting perfect load acceleration. 4 ) Due to the high value of the breakdown torque, momentary load peaks and temporary voltage drops are accepted without any sudden speed loss. This is a fundamental requirement for the performance of ma...

Depending on the electric connection configuration, a three-phase induction motor can operate at any direction of rotation. The direction of rotation can be reversed by exchanging the position of two of the connecting leads. WEG motors are supplied with bi-directional fans unless only one direction of rotation is informed on the data sheet or on additional nameplates. In general the motor allow the operation at any direction of rotation without affecting the motor cooling. Motors without fan, but ventilated by the own load ( the fan is the load ) must meet the cooling requirements of the motor, independent of the direction of rotation.

ADVANTAGES OF AUTO TRANSFORMER STARTER: a ) On the 65% tapping the line current is approximately equal tp that of a Star-Delta starter, however, at the time of switching from reduced voltage to the full supply voltage, the motor is not disconnected so that the second peak is very much reduced since the transformer is converted into reactance for a short time. b ) It is possible to vary the tapping from 65% to 80% or even up to 90% of the supply voltage in order to ensure that the motor starts satisfactorily. DISADVANTAGES OF AUTO TRANSFORMER STARTER: a ) One of its great disadvantages is the limitation of its operation frequency. It is always necessary to know the operation frequency in order to determine a suitably rated auto-transformer. b ) The compensating switch is much more expensive than a Star-Delta starter due to the auto-transformer. c ) Due to the size of the auto-transformer starter, much larger control panels are required which increases the price.

ADVANTAGES OF STAR DELTA STARTER: a ) Star-Delta starters are widely used due to their relatively low price. b ) There are no limits to the number of times they can be operated. c ) The components require very little space. d ) The starting current is reduced to approximately one-third. DISADVANTAGES OF STAR DELTA STARTER: a ) The starter can only be applied to motors where the six leads or terminals can be accessed. b ) The supply voltage must be the same as the rated motor voltage for Delta connection. c ) Because the starting current is reduced to approximately one-third of the rated current, the starting torque is also reduced to one-third. d ) If the motor does not reach at least 90% of its rated speed at the time of switching from Star to Delta the current peak will be as high as in a D.O.L. start, thus causing harmful effects to the contacts of the contactors and the connection system brings no advantage to the electrical system.

Whenever possible a squirrel cage three-phase motor should be started direct-on-line ( D.O.L. ) by means of contactors. It must be taken into account that for a certain motor the torque and current values are fixed, irrespective the load, for a constant voltage. In cases where the motor starting current is excessively high, harmful consequences may occur: a ) High voltage drop in the power supply system. Due to that, equipment connected to the system may be affected; b ) The protection system ( cables, contactors ) must be over designed resulting in higher cost; c ) Utilities regulations limiting the line voltage drop. If D.O.L starting is not possible due to these problems, indirect connection system can be used so as to reduce starting current. Star-delta switch Compensating switch Series-parallel switch Electronic start ( Soft-Starter )

Considering that an induction motor is a simple designed and rugged construction machine, its life time will exclusively depend on the quality level of the insulation materials. Motor insulation is affected by several factors including moisture, vibration, corrosive environments and others. Among all these factors, operating temperature of the insulating materials is the most critical. The motor life time is reduced by half when subject 8% to 10 oC in operation above the rated temperature of the class of insulating material. To ensure a longer lifetime for the electric motor, the use of thermal sensors is recommended for the winding protection. When we refer to motor life time reduction, we do not refer specifically to excessively high temperatures resulting in sudden insulation burn out. Insulation life time ( in terms of operating temperature much below than the one affecting the insulation ) refers to permanent aging of the insulation material which becomes dry and loses its insulat...

The electric motor is a machine capable of converting electrical energy into mechanical energy. The induction motor is the most widely used type of motor, because it combines all the advantages offered by the electrical energy such as low cost, easy of supply and distribution, clean handling and simple controls - together with those of simple construction and its great versatility to be adapted to wide ranges of loads and improved efficiencies. The most common types of electric motors are: A ) DIRECT CURRENT MOTORS These motors are quite expensive requiring a direct current source or a converting device to convert normal alternating current into direct current. They are capable of operating with adjustable speeds over a wide range and are perfectly suited for accurate and flexible speed control. Therefore, their use is restricted to special applications where these requirements compensate the much higher installation and maintenance costs. B ) ALTERNATING CURRENT MOTORS These are t...

A single prime mover – generator and substation No need for electric transmission connection to the wind farm (only to the Expandera-generator),  Wind turbine gear box requirements are greatly simplified (since the speed/torque characteristics of a wind turbine rotor are better matched to an air compressor than a generator). No need for natural gas or an industrial waste heat source.  No need for cooling water (solar thermal plants typically use steam as working fluid so condenser cooling water is needed).  Also, since wind energy production in West Texas tends to be higher in winter and spring, and solar is highest in summer months, seasonal fluctuations in energy supply tend to even out when the two sources are combined in an integrated system.

Using the sun to dry crops and grain is one of the oldest and most widely used applications of solar energy. The simplest and least expensive technique is to allow crops to dry naturally in the field, or to spread grain and fruit out in the sun after harvesting. The disadvantage of these methods is that the crops and grain are subject to damage by birds, rodents, wind, and rain, and contamination by windblown dust and dirt. More sophisticated solar dryers protect grain and fruit, reduce losses, dry faster and more uniformly, and produce a better quality product than open air methods. The basic components of a solar dryer are an enclosure or shed, screened drying trays or racks, and a solar collector. In hot, arid climates the collector may not even be necessary. The southern side of the enclosure itself can be glazed to allow sunlight to dry the material. The collector can be as simple as a glazed box with a dark colored interior to absorb the solar energy that heats air. The air heate...

Solar stills are systems designed to filter or purify water. The number of systems designed to filter water have increased dramatically in recent years. As water supplies have increased in salinity, have been contaminated, or have experienced periods of contamination, people have lost trust in their drinking water supply. Water filtration systems can be as simple as a filter for taste and odor to complex systems to remove impurities and toxins. Solar water distillation is one of the simplest and most effective methods of purifying water. Solar water distillation replicates the way nature purifies water. The sun's energy heats water to the point of evaporation. As the water evaporates, purified water vapor rises, condensing on the glass surface for collection. This process removes impurities such as salts and heavy metals, as well as destroying microbiological organisms. The end result is water cleaner than the purest rainwater. Solar energy is allowed into the collector to heat th...

Solar Thermal power is heat energy obtained by exposing a collecting device to the rays of the sun. A solar thermal system makes use of the warmth absorbed by the collector to heat water or another working fluid, or to make steam. Hot water is used in homes or commercial buildings and for industrial processes. Steam is used for process heat or for operating a turbine generator to produce electricity or industrial power. There are several basic kinds of solar thermal power systems including “flat plate” solar water heaters; concentrating collectors, such as central tower receivers; and parabolic trough and dish collectors. FLAT PLATE SOLAR WATER HEATERS Water flows through tubes that are attached to a black metal absorber plate. The plate is enclosed in an insulated box with a transparent window to let in sunlight. The heated water is transferred to a tank where it is available for home, commercial or institutional use. CENTRAL TOWER RECEIVERS In order to produce steam ...

Photovoltaic are solar cells that produce electricity directly from sunlight. The solar cells are made of thin layers of material, usually silicon. The layers, after treatment with special compounds, have either too many or too few electrons. When light strikes a sandwich of the different layers, electrons start flowing and electric current results. Photovoltaic are used throughout the nation and elsewhere to operate appliances, provide lighting, and to power navigation and communication aids. Photovoltaic panels provide power for equipment in space ships and satellites. PV cells supply power needed to operate many kinds of consumer products such as calculators and watches. Photovoltaic systems provide electricity to remote villages, residences, medical centers, and other isolated sites where the cost of photovoltaic equipment is less than the expense of extending utility power lines or using diesel-generated electricity.

ADVANTAGES OF SOLAR ENERGY: Solar energy makes use of a renewable natural resource that is readily available. Solar power used by itself creates no carbon dioxide or other toxic emissions. Use of solar thermal power to heat water or generate electricity will help reduce the Territory’s complete dependence on fossil fuels. Solar water heaters are an established technology, readily available on the commercial market, and simple enough to build, install and maintain by yourself. The production of electricity by the photovoltaic process is quiet and produces no toxic fumes. PV cells generate direct-current electricity that can be stored in batteries and used in a wide range of voltages depending on the configuration of the battery bank. Although most electric appliances operate on alternating current, an increasing number of appliances using direct current are now available.  Where these are not practical, PV-generated direct current can be changed into alter...

Solar energy is energy that comes from the sun. Every day the sun radiates an enormous amount of energy. The sun radiates more energy in one second than people have used since the beginning of time. All this energy comes from within the sun itself. Like other stars, the sun is a big gas ball made up mostly of hydrogen and helium. The sun generates energy in its core in a process called nuclear fusion. During nuclear fusion, the sun’s extremely high pressure and hot temperature cause hydrogen atoms to come apart and their nuclei to fuse or combine. Some matter is lost during nuclear fusion. The lost matter is emitted into space as radiant energy. It takes millions of years for the energy in the sun’s core to make its way to the solar surface, and then approximately eight minutes to travel the 93 million miles to earth. The solar energy travels to the earth at a speed of 186,000 miles per second, the speed of light. Only a small portion of the energy radiated by the sun i...

REGULAR MAINTENANCE: There is very little maintenance required on a PV system with no moving parts. Some system owners wash their panels, but in the Northwest, our climate tends to take care of this chore. You may want to brush off the panels if they tend to collect leaves, but other than that, your system should operate as designed with no intervention. You can also keep track of your production by reading your production meter or checking the inverter display. RESALE VALUE: The affect of a solar system on the appraised value of your home can be hard to predict, but according to a study by ICF Consulting, every $1,000 reduction in annual energy bills increases a home’s resale value by $10,000 to $25,000. However, homes are generally valued in comparison to similarly sized and aged homes around them, and if there aren't many solar homes in your neighborhood, the appraiser may not have a bar to measure against. The market for solar homes continues to grow as energy costs increase al...

Three core factors affect the sizing of your system: your electricity usage, space availability on your property, and your budget. YOUR ELECTRICITY USAGE Do you want to try to produce 100% of your power or some smaller percentage? While any excess production from month to month will carry over as a credit on your utility bill (net metering), you will not want to install a system that produces more than 100% of your power as the utility will not reimburse you for excess power produced at the end of the year. You may also not want to size the system too large if you are planning more energy conservation measures for the future. To determine how much power you use right now, look for the kilowatt-hour (kWh) consumption on your utility bill. Sum the kWh for the past year to get your annual electricity usage. Space Availability The amount of unshaded, easy-to-access, space available for mounting panels will limit the size of the system. You can use In My Back Yard (IMBY), an online t...

A well-designed solar electric system has clear and unobstructed access to the sun for most of the day throughout the year. Siting a PV system correctly is critical in order to achieve maximum power production and thus maximum energy offset and financial return. Orientation and Tilt Optimal orientation for solar panels is true south. As you move away from true south, a system will suffer production losses, up to as much as 15–25% for panels oriented east or west. However with advancements in technology these losses are decreasing as inverter manufacturers learn how to maximize off-of-south orientations. In Seattle, solar panels produce the maximum power annually when mounted at a tilt of roughly 30 degrees. Shading Avoid shading as much as possible. Even minimal shading can significantly impact power production. You will want to consider potential shading from trees, buildings, power lines, telephone poles, and obstructions like chimneys and vent pipes. Your contractor should inclu...

A PV System includes: 1. PV ARRAY Multiple PV panels installed together are called a PV array. Mounting arrays to rooftops is most common, yet they can also be located on a pole, a ground mounted rack, parking area shade covers, window awnings, etc. The PV array produces Direct Current (DC) power. 2. DC DISCONNECT The DC Disconnect is a safety device that, when manually opened, stops power running from the array to the rest of the system. The DC disconnect is used during system installation and anytime your contractor needs to work on the system. 3. DC/AC INVERTER The PV array produces DC electricity, however, we use Alternating Current (AC) electricity in our buildings and power grid. The Inverter converts the DC power to AC power. 4. AC DISCONNECT The AC Disconnect is another safety device and is often incorporated into the Inverter. Seattle City Light does not require an AC Disconnect on most small residential systems. (For details on this exemption, contact your Electric Se...

The first solar cell was created in 1883. It was inefficient by today’s standards, converting only 1–2% of sunlight into electricity. The breakthrough in solar cell technology came in 1954 when researchers at Bell Laboratories stumbled across the photo voltaic (or PV) properties of silicon while experimenting with new transistor technologies. Three years later, PV research began in earnest to develop an independent solar energy source for space technologies. Thanks to continuing research, modern commercial PV cells have improved to 11–15% efficiency. Historically, PV has been used extensively in areas that are not served by a power grid. As PV prices have dropped, and grid energy has become more expensive, PV systems are increasingly used in grid-tied applications. A solar electric or PV cell uses a semiconductor material similar to that used in computer chips to absorb sunlight and convert it into electricity. Multiple solar cells are linked together to form a module or panel. Multipl...

􀂃 Solar electric systems are safe, reliable, pollution free, and use a renewable source of energy—the sun. Most systems have no moving parts and are increasingly easy to install. 􀂃 The option of net metering, or interconnecting a customer generating system to the utility grid, makes solar electric systems more economically viable. 􀂃 Landmark federal and state legislation have created new financial incentives for owning and operating a solar electric system. If you are interested in making a long-term investment to protect yourself from rising energy costs and want to reduce your personal environmental impact, now may be the time to learn more about installing a solar electric system for your home or business.

THERMOSOLAR ENERGY: Thermosolar Energy is a technology for harnessing solar energy for heat (at low temperature); it is mainly used for the production of hot water in residential buildings, to heat water in swimming pools and for climatization plants and other application.THERMOELECTRIC ENERGY: Thermoelectric Energy: (Solar thermal power) is a technology that uses the sun rays to heat a fluid, from which heat transfer systems may be used to produce steam. The steam, in turn, is converted into mechanical energy in a turbine and into electricity from a conventional generator coupled to the turbine.