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There are some applications where phase sequence required to be changed in 3-Phase motors. Mostly plants which don’t have their own power supply and take from Power Distribution companies phase sequence might change. That Phase sequence can be easily changed in 3-Phase Induction motors by changing two phases from Input Source supply. In Case of Star-Delta Starters 6 no. leads enter into motor so in that case Phase sequence can be changed by changing 2 no. of phases in each pair of 3-Phases. Star-Delta Starter Phase Sequence changed in Star-Delta Starter:- In Case of DOL Soft-Starters Phase sequence can be changed by changing phases in Mains Supply. Is there is requirement of changing Phase sequence in VFD’S???? Answer for the same in that there is no need of changing phase sequence. In Case of VFD there is no need of changing phase sequence as in that case 3-Phase supply is converted into DC supply thereafter that can be converted into AC supply again so

It is very important to find  out electrical parameters for an electrical engineer. Very time installation of motor required certain parameters calculations which are stated as below:- Electrical Parameter to Find Alternating Current Single-Phase Three-Phase Amperes when horsepower is known HP x 746 E x Eff x pf HP x 746 1.73 x E x Eff x pf Amperes when kilowatts are known KW x 1000 E x pf KW x 1000 1.73 x E x pf Amperes when KVA are known KVAx 1000 E KVA x 1000 1.73 x E Kilowatts I x E x pf 1000 1.73 x I x E x pf 1000 KVA I x E 1000 1.73 x I x E 1000 Horsepower = (Output) I x E x Eff x pf 746 1.73 x I x E x Eff x pff 746 As from above we can find out ampere a motor can take. Day to day checking motor ampere is very much required for an electrical engineer.

There are following formula's which are very useful for an electrical engineer while doing calculation on various aspects for induction motors. High Inertia Loads t = WK 2 x rpm 308 x Tav. WK 2 = inertia in lb.ft. 2 t = accelerating time in sec. T = Av. accelerating torque lb.ft.. T = WK 2 x rpm 308 x t For calculating time required to accelerate an induction motor at a particular load formula-I will help the same If you know want a particular motor to get accelerated at a given time then required torque can be calculated by using formula-II in above. Both formulas are quite helpful while doing programming in Variable frequency drives and soft-starters. Inertia reflected to motor = Load Inertia X ( Load rpm / Motor rpm ) X ( Load rpm / Motor rpm ) Synchronous Speed, Frequency And Number Of Poles Of AC Motors n s = 120 x f   P f = P x n s 120 P = 120 x f   n s Relation Between Horsepower, Torque, And Speed HP = T x

Rules Of Thumb (Approximation) At 1800 rpm, a motor develops a 3 lb.ft. per hp At 1200 rpm, a motor develops a 4.5 lb.ft. per hp At 575 volts, a 3-phase motor draws 1 amp per hp At 460 volts, a 3-phase motor draws 1.25 amp per hp At 230 volts a 3-phase motor draws 2.5 amp per hp At 230 volts, a single-phase motor draws 5 amp per hp At 115 volts, a single-phase motor draws 10 amp per hp Mechanical Formulas Torque in lb.ft. = HP x 5250 rpm HP = Torque x rpm 5250 rpm = 120 x Frequency No. of Poles Temperature Conversion Deg C = (Deg F - 32) x 5/9 Deg F = (Deg C x 9/5) + 32 

Can ever imagine how dangerous are electrical faults??? Let me give you one fact about electrical faults and their levels. Temperature produced during electrical arc-flash can reach 35,000 _F (19,500 _C).  These extremely high temperatures will easily melt copper conductors. Copper expands by a factor of 67,000 times at such high temperatures Usually such faults occurred during Short circuit of copper bus bars. When Human comes directly short circuit with two phases. The dangers associated with these faults are:- 1. High pressures 2. High level of Sound 3. Very high currents These high pressures can easily exceed 100-1000  pounds per square foot. Such faults produce high sounds which seems like a bomb get blasted and even causes damages to ladders, Humans etc. The sounds associated with these pressures can exceed 160 dB. The electrical current levels associated with electrical shock are measured in milli-amperes or one-thousandth of an ampere (0.001 Amps). Electrical current flows thro

Both Cables are widely used in Industries: PVC - stands for polyvinyl chloride  XLPE - is cross linked polyethylene cable.  Main Thumb rule for differentiation is that XLPE cables can be used for both HT and LT lines. But PVC Cables can be used only for LT lines. XLPE can withstand a higher temperature than PVC without detriment. This means that more current can be conducted for the same cross sectional area of copper. This means a big saving in cables costs.  Visit link below for more details:- http://electrialstandards.blogspot.com/2014/04/66kv-to-132kv-tests-requirement.html http://electricalsystembasics.com/2014/04/xlpe-cables-advantages-oil-filled-paper-insulated-cables.html XLPE Cables useful properties are :- XLPE Cables construction:- 1.Temperature  resistance 2. Stress rupture resistance  3. Environmental stress crack resistance  4. Resistance to U .V light 5. Chemical resistance 6. Oxidation resistance   XLPE Cables can  be useful for following applications:-  1) XLPE cables

Its quit confusing sometimes to read Nomenclature of cables such as YWY or AYFY. Below is Details of that Nomenclature which will help to read about cables nomenclatures and will ease out for Technical specifications of cables. A = Appearing as a first letter denotes Aluminium Conductor. Y = TROPODUR means PVC Insulation if appears any where in configuration but not at last if Y is written at last then it means TROPODUR Sheath. 2X = TROPOTHEN-X (Cross-linked Polyethylene) Insulation. W = Round Steel Wire Armouring. WW = Double Round Steel Wire Armouring. F = Formed Steel Wire (Strip) Armouring. FF = Double Formed Steel Wire (Strip) Armouring. C = Metallic Screening (Usually of Copper). CE = Metallic Screening (usually of Copper) over each individual core. Gb = Holding Helix Tape (of Steel) Wa = Aluminium Round Wire & Aluminium Formed Wire (Strip) Fa Armouring b) Type Designations : AYY Aluminium Conductor, TROPODUR Insulated, TROPODUR Outer Sheathed Heavy Duty  Cables. AYWY Alumin

IEC 60134 à Absolute maximum and design ratings of tube and semiconductor devices IEC 60137 à Bushings for alternating voltages above 1000V IEC 60146 à Semiconductor Converters IEC 60169 à Radio-frequency connectors IEC 60183 à Guide to the selection of high voltage cables IEC 60204 à Safety of machinery IEC 60214 à On-load tap changers IEC 60228 à Conductors of insulated cables IEC 60233 à Tests on Hollow Insulators for use in Electrical Equipment IEC 60238 à Edison screw lampholders IEC 60245 à Rubber-Insulated Cables IEC 60255 à Electrical Relays IEC 60268 à Sound system equipment IEC 60269 à Low voltage fuses IEC 60270 à High-Voltage Test Techniques - Partial Discharge Measurements IEC 60287 à Calculation of permissible current in cables at steady state rating IEC 60092-350 à Shipboard Power cables-General construction and Test Requirements IEC 60296 à Mineral Insulating oils for transformers & switchgear IEC 60297 à 19-inch rack IEC 60298 à high voltage swi

IEC 60027 à Letter symbols to be used in electrical technology... IEC 60034 à Rotating electrical machinery IEC 60038 à IEC Standard Voltages IEC 60044 à Instrument transformers IEC 60050 à International Electrotechnical Vocabulary IEC 60062 à Marking codes for resistors and capacitors IEC 60063 à Preferred number series for resistors and capacitors IEC 60065 à Audio, video and similar electronic apparatus - Safety requirements IEC 60068 à Environmental Testing IEC 60071 à Insulation Co-ordination IEC 60073 à Basic Safety principles for man-machine interface, marking and identification IEC 60076 à Power Transformers IEC 60079 à Parts 1-14 Electrical Installations in Hazardous Areas IEC 60085 à Electrical insulation IEC 60086 à Primary batteries IEC 60094 à Magnetic tape sound recording and reproducing systems IEC 60096 à Radio-frequency cables IEC 60098 à Rumble measurement on Vinyl Disc Turntables IEC 60099 à Surge arresters