Type NumberTongue Width (cm)Window Area (Sq. Cm)Type NumberTongue Width (cm)Window Area (Sq.
Cm)171.271.86512A1.5881.8979A2.2237.8.28411A1.9059.0.7234A3.0.8911.5883.3.8.7.4394AX2.52.544.84.11732.5415.865142.546.9.3.52935A3.8139.803For operation on mains supply, the frequency is 50HZ, while the flux density can be taken as 1Wb/sq cm. For ordinary Steel stampings and 1.3Wb/sq cm for CRGO stampings, depending on the type to be used.Hence. Primary turns (n1) = Turns per volt(Tpv). Primary voltage(V1). Secondary turns (n2) = Turns per volt(Tpv).
. The above equation is the output equation of three phase transformer. EMF PER TURN. The transformer design starts with selection of an appropriate value for emf per turn. Hence an equation for emf per turn can be developed byrelating output kVA, magnetic and electric loading.
secondary voltage(V2). 1.03 (Assume that there is 3% drop in transformer windings). The width of the tongue of laminations is approximately given by:-Tongue width (Tw) = Sqrt. (GCA) Current densityIt is the current carrying capacity of a wire per unit cross sectional area. It is expressed in units of Amp/ cm².
The above mentioned wire table is for a continuous rating at current density of 200A/cm². For non-continuous or intermittent mode of operation of transformer one can choose a higher density up to 400A/cm² i.e., twice the normal density to economize the unit cost. It is opted as, the temperature rise for the intermittent operational cases are less for the continuous operational cases.So depending on the current densities choosen we now calculate the values of primary and secondary currents that are to searched in wire table for selecting SWG:-n1a = Primary current (Ip) calculated / (current density/200)n2a = Secondary current (Is) calculated / (current density/200)For these values of primary and secondary currents we choose the corresponding SWG and Turns per sqcm from the wire table. Then we proceed to calculate as follows:-. Primary area(pa)= Primary turns(n1) / (Primary turns per sqcm). Secondary area(sa)= Secondary turns(n2) / (Secondary turns per sqcm).
The total window area required for the core is given by:-Total area (TA) = Primary area (pa) + Secondary area (sa). Extra space required for the former and insulation may be taken as 30% extra space of what is required by the actual winding area.
This value is approximate and may have to be modified, depending on the actual winding method.Window area (Wacal) = Total area (TA). 1.3For the above calculated value of tongue width, we choose core number and window area from the core table ensuring that the window area chosen is greater than or equal to the Gross core area. If this condition is not satisfied we go for a higher tongue width ensuring the same condition with a corresponding decrease in the stack height so as to maintain approximately constant gross core area.Thus we get available tongue width (Twavail) and window area ((avail)(aWa)) from the core table. Stack Height = Gross core area / Tongue width ((available) (atw)).For commercially available former size purposes, we approximate stack height to tongue width ratio to the nearest following figures of 1.25, 1.5, 1.75. At the worst case we take the ratio equal to 2. However any ratio till 2 can be taken which would call for making ones own former.If the ratio is greater than 2 we select a higher tongue width (aTw) ensuring all the conditions as above. Stack height(ht) / tongue width(aTw) = (some ratio).
Modified stack height = Tongue width(aTw). Nearest value of standard ratio. Modified Gross core area = Tongue width (aTw). Modified stack height.Same design procedure applies for control transformer, where in we need to ensure that stack height equals Tongue width.Thus we find core number and stack height for the given specifications. Designing a transformer using an example:.
The given details are as follows:-. Sec.
About Jignesh.ParmarJignesh Parmar has completed M.Tech (Power System Control), B.E(Electrical). He is member of Institution of Engineers (MIE) and CEng,India.
Membership No:M-1473586.He has more than 16 years experience in Transmission -Distribution-Electrical Energy theft detection-Electrical Maintenance-Electrical Projects (Planning-Designing-Technical Review-coordination -Execution). He is Presently associate with one of the leading business group as a Deputy Manager at Ahmedabad,India. He has published numbers of Technical Articles in “Electrical Mirror”, “Electrical India”, “Lighting India”,”Smart Energy”, “Industrial Electrix”(Australian Power Publications) Magazines. He is Freelancer Programmer of Advance Excel and design useful Excel base Electrical Programs as per IS, NEC, IEC,IEEE codes. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & Knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.
Jignesh Parmar has completed M.Tech (Power System Control), B.E(Electrical). He is member of Institution of Engineers (MIE) and CEng,India. Membership No:M-1473586.He has more than 16 years experience in Transmission -Distribution-Electrical Energy theft detection-Electrical Maintenance-Electrical Projects (Planning-Designing-Technical Review-coordination -Execution). He is Presently associate with one of the leading business group as a Deputy Manager at Ahmedabad,India. He has published numbers of Technical Articles in “Electrical Mirror”, “Electrical India”, “Lighting India”,”Smart Energy”, “Industrial Electrix”(Australian Power Publications) Magazines. He is Freelancer Programmer of Advance Excel and design useful Excel base Electrical Programs as per IS, NEC, IEC,IEEE codes. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages.
He wants to Share his experience & Knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics. Archives. (1). (2). (2).
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