While supplying the nonlinear loads, harmonic currents flow in the transformer and to protect the windings and transformer oil from overheating, load on it needs to be reduced. Rating of transformers supplying harmonic rich loads. Factor k in europe, the transformer derating factor is calculated according to the formulae in bs 7821 part 4. Kfactor is a mathematical representation to characterize a transformers ability to withstand. Standard and custom designs through 10 mva, up to 35kv. K factor distribution transformers in north america are subject to minimum efficiency regulations in both the u. Transformers course to be more familiar with the contents of our new articles about the power and distribution transformers sizing calculations.
The k factor is a number calculated from the harmonic spectrum of the current in a load waveform such that, regardless of the actual spectrum, loads that require the same k factor have the same heating effect on the transformer. It is a k factor calculator developed by the new zealand company knac solutions. No load losses of a distribution transformer under harmonic loads can increase its operating cost. What is k factor and what does it mean regarding transformers. Calculating the prospective short circuit current 4. In this standard, the k factor is defined and its method of calculation shown. Calculating overcurrent protection device rating on the low voltage side of the transformer. Kfactor measures the heating effects of harmonics on transformer loading and losses.
A kfactor rated transformer is one which is used to deal with harmonic generating loads. A case study for selection and sizing of k rated isolation transformers in parallel redundant ups system. Pdf a study of kfactor power transformer characteristics by. Dry type distribution transformers solahd k factor transformers are designed to reduce the heating effects of harmonic currents created by loads like those shown in chart a. Power transformer kfactor understand the importance of power transformers k factor and follow these simple steps to verify transformer content and load.
K factor must be determined to calculate the right size transformer that is needed. As from the formula, while calculating the kfactor, the harmonic current is getting multiplied by the square of its number. These type of loads generate harmonic currents that cause transformers and system neutrals to overheat, which can destroy the transformer. The harmonic analysis module also offers the transformer kfactor ansiiec and factork bs calculation for the assessment of transformer rating with respect. K factor is a weighting of the harmonic load currents according to their effects on transformer heating, as derived from ansiieee c57. In short, k factor is a weighting of the harmonic load currents according to their effects on transformer heating, as derived from ansiieee c57. Short answer is the k factor conveys a transformers ability to serve varying degrees of nonlinear loads without exceeding the rated temperature rise limits. Krated transformer manufacturers mumbai india neelkanth power. All sheet metal workers know the importance of an accurate k factor or bend allowance when it comes to design. Only the fundamental oscillation is used in order to calculate the cosphi. It is important to have systems in place to monitor and analyze the power quality issues that can affect critical and expensive components in a power distribution system.
Miscellaneous documents power quality international. By downloading this spreadsheet you agree to the following terms. To increasedecrease the alternating volts in electric power, transformers are used. Rus bulletin 1724e301 guide for the evaluation of large. Underwriters laboratories recognized the problems with derating. K factor calculation depends upon the fundamental current and the harmonic current components, and it is an indicative value of the harmonic contents in the power system. The k factor transformer is an isolating transformer that can be loaded at 100% of load plus the harmonics load without overheating. It has two types, single phase and three phase transformer. Determination of transformer rating 52 temperature increases also reduce the power factor, productivity, efficiency, capacity and performance of the plant. Neel industrial systems k rated isolation transformer. Significance of k factor k factor of the electrical distribution network is the reason why transformers need to be derated. K factor transformers are specially assembled with a double sized neutral conductor, heavier gauge copper and either change the geometry of their conductors or use multiple conductors for the coils. Kfactor transformers are specially designed to accommodate harmonic.
I came across a community sponsored application that will aid any sheet metal designer. Significance of k factor in circuit breaker ratings powell industries, inc. The kfactor transformer power quality in electrical. Collection of formulas for umg measurement devices janitza. Alfa offers a complete range of new and reconditioned low voltage dry type transformers including general purpose, drive isolation, motorstarting autotransformers. The k rating number of the transformer 1, 4, 9, 20 is in indication of the amount of harmonic current the transformer is capable of handling. As the k factor of the transformer increases, generally the size and cost increase, low load efficiency k factor transformers are designed to withstand the extra heating and higher neutral currents caused by harmonics created by nonlinear loads such as vfd, dc power supplies and led lighting. Transformer capacity calculator three phase transformer.
Significance of k factor in circuit breaker ratings. An online three phase transformer calculator to find the current in different power units. A specific k factor rating indicates that a transformer can supply its rated kva load output to a load with a specified amount of harmonic content. Eaton s kfactor transformers address the problems caused by nonlinear loads and harmonics. K 40 k factor transformers are designed to be operated fully loaded with any harmonic load having a k factor equal to or less than its k rating. It is important to note, however, that these solutions are best only for those experts who have knowledge and experience with assembly transformers. K factor is the right company, iso9001 certified, reliable and. Calculating the prospective short circuit current across the low voltage side of the transformer. K factor is a unit measuring a transformer s ability to withstand the harmonics content of a system. Lft transformer loss factor which is the ratio of average transformer losses to peak transformer losses.
To download your copy of transformer calculations spreadsheet, click on. As long as the load k factor is lower than the k rating of the transformer, the full kva rating of the transformer can. In this paper, the formulations how to calculate the maximum permissible rms nonsinusoidal load current i max using the harmonic loss factors f hl and k factor were introduced. If you have some experience in assembling transformers, then this program is perfect for you. Find, read and cite all the research you need on researchgate. Mks mksh single phase kfactor dry type distribution. Equivalence table between k factor ul 1562 and over rating factor. Kfactor transformer, also known as k rated transformer, is designed for nonlinear or harmonic generating loads that a standard transformer could not adequately handle due to overheating. Calculate size of transformer and voltage due to starting of large size motor new.
A k factor transformer is designed to handle harmonic content in its load current without exceeding its operating temperature limits. Once the k factor of the load has been determined, it is a simple matter to specify a transformer with a higher k rating from the standard range of 4, 9, 20, 30, 40, 50. Professionals with experience in transformer assemblies use the computer program to calculate the number of coils and wire thickness. There are two widely used methods to calculate the kfactor. Are you looking for the best transformer calculator software for your next project. The k factor rating is an index of the transformer s ability to withstand harmonic content while operating within the temperature limits of its insulating system. Visit our website to view the publications listed below, download the software.
The derating measure for normal transformers is always taken to limit the temperature of windings or topoil. Today, we will explain other special cases for power and distribution transformers sizing calculations. Power and distribution transformers sizing calculations part seven. In the case of sinusoidal loading of the transformer the k factor 1. Three phase isolation transformers from 1 to 40kva. A study of k factor power transformer characteristics by modeling simulation.
To download your copy of transformer calculations spreadsheet, click on the link. If you dont know anything about assembling transformers, please dont use calculations from this program for building your own transformer. This k factor has absolutely nothing to do with the k factor used to determining the suitability of a transformer for use in a circuit with high harmonic levels. The blakley calculator allows you to carry out various electrical calculations. Calculating overcurrent protection device rating 3. Sola kfactor transformers are designed to reduce the heating effects of harmonic currents. Once the k factor is determined, it is used in the design of the transformer to compensate for the additional heating effects generated by the harmonic currents. The higher the k factor, the greater the harmonic heating effects. Kfactor can be a misleading power quality indicator. Nowadays, in industrial workplaces, the proliferation of solidstate devices lighting reactors, motor drive and control systems, communications equipments, and other dc motor loads have created some relevant problems for specification engineering, contractors and business owners. Explains why hmts can be better than k rated transformers.
K peak responsibility factor which is the ratio of transformer load at the time of the system peak to the transformer peak load. Alfa transformer stocks remanufactured and reconditioned, threephase, medium voltage dry type transformers through 2500 kva. Power factor correction calculations for power system new star. Harmonics generate additional heat in the transformer and cause non k rated transformers to overheat possibly causing a fire, also reducing the life of the transformer. Transformer calculation is program for calculating number of coils and wire thickness at transformer. The losses generated by the harmonics can be calculated by multiplying the k factor by the stray losses. Loading transformers with non sinusoidal currents kfactor. Tti three phase isolation transformers from 1 to 40kva. Kfactor rated transformers electrical harmonics eaton. A transformer with k factor 9 should be specified when 100% of the load is nonlinear. The k factor rating is an index of the transformers ability to withstand harmonic content while operating within the temperature limits of its insulating system. These type ql transformers have passed the ul k factor testing program.
The kfactor transformer power quality in electrical systems. A kfactor rated transformer is designed to handle a degree of harmonic load currents without overheating. Barrere exality corporation a transformer with individual winding inductances l1 and l2 has mutual inductance m between the windings. Download transformer calculator coils and wire thickness. K factor transformers are specially assembled with a double sized neutral conductor, heavier gauge copper and either change the geometry of their conductors or use multiple conductors for the. Comparing transformer derating computed using the harmonic. They also compensate for stresses on a transformer s winding insulation which prevents insulation breakdown and premature failure. There are many different loads such as computers, solidstate devices and motors which cause a non linear load. Electrical ms excel spreadsheets electrical engineering portal. For example, a k transformer can be fully loaded with any harmonic load having a k factor up to k. Transformers with a rated k factor of 4, 7, 20 and 30 are available. The transformer losses will increase while it is supplying nonlinear load current. Determination of transformer rating based on total. The online free fabrication calculator will help you calculate the k factor, y factor, bend allowance, bend deduction, flat size, neutral axis, arc length etc.
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