BC=651.85A, AC=651.84A, supply voltage 220 line to line. Formula for Voltage | How to calculate Potential Difference. calculations or measurements and from either phase parameters or line parameters. To protect the windings of a transformer against overcurrent, use the percentages listed in Table 450.3(B) and its applicable notes. If sending end voltage and load PF are known. I'm not sure if this helpful, but I will derive the formulae using the above method so you can see the two tie together. I've always been bad a remembering formulae, so I prefer to remember concepts/methods. In a three phase system, the amount of current going through one of the phases is not a fraction of the amount of current going through all three? I expect it to stay the same. Initially, we explored the idea of three-phase power systems by connecting three voltage sources together in what is commonly known as the “Y” (or “star”) configuration.. is it possible to find the power factor given the reactive power(VAR) and real power(KW) by this equation? Through a circuit, a current of 9A flows through that carries a resistance of 10 \(\Omega\). This configuration of voltage sources is characterized by a common connection point joining one side of each source. If you are looking at it on a phase by phase you may need to be a little careful. Sir, when a voltage dip occurs current increases, so instead of dimming, a bulb should glow brighter but the reverse thing happens, why? The current is simply the kVA divided by the voltage. Only emails and answers are saved in our archive. If you have some expert knowledge or experience, why not consider sharing this with our community. Voltage Drop Formulas and Calculation. Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications! VD = \(\frac{2 LRI}{ 1000 \times 0.866}\) Here, L = refers to the length of the circuit R = refers to the resistance in Omega (\(\Omega\)) I = refers to the load current in amperes. What normally happens in star is that because the voltage is less across each winding, you end up delivering less power then you would in delta (less power is less current). Wapplied = 3 Uln I cos Φ                    (2), For pure resistive load and power factor = 1 the real power in a 400/230 voltage (line to line / line to neutral) 20 amps circuit can be calculated as, WBHP = 31/2 U I PF μ / 746                       (3). Similarly a transformer (with three windings, each identical) supplying a given kVA will have each winding supplying a third of the total power. Assuming 577 V is Line Voltage and load is balanced. You would have 208 volts across each of the loads you gave and can find the current using Ohm’s law (i.e. I know that it is right but how can i used it to find the value of complex power?? By measuring voltages from Line 1 to Line 2, Line 2 to Line 3, and Line 3 to Line 1, and performing a few simple calculations, a technician can determine if there is a voltage unbalance problem. I try not to think like that as it confuses me as well and there is sometimes more to it than that. That 60A is total rms current for a single phase, not the peak current, correct? To protect the windings of a transformer against overcurrent, use the percentages listed in Table 450.3(B) and its applicable notes. This is done all the time (fridge or toilet extract fan in your house for example). To calculate kVA, you need to enter the known values of voltage and the current into the respective fields. When selecting a cable, the performance of the cable under fault conditions is an important consideration. three phase power is 36 kW,  single phase power = 36/3 = 12 kW The... Here’s list of some famous scientists. The first formula is used more often because it is generally more convenient to obtain line values of volt- age and current, which can be measured with a voltmeter and clamp-on ammeter. Because you have an unbalanced system, you will have some current in the neural line. When Wire length is in meters. Also depends on if it is three phase or single phase and the voltage. If the system is perfectly balanced I again have no issues figuring out the amps drawn on each leg. So is it as simple as multiply by 3 to get the total, 3-phase rms current? Single & Three Phase Line kVA calculator is an online tool used in electrical engineering to measure the unknown quantity by two known quantities applied to the below formulas for single phase and three phase connection. From All About Circuits: In balanced “Y” circuits, line voltage is equal to phase voltage times the square root of 3 In balanced “Δ” circuits, line voltage is equal to phase voltage: *ignore Iline and Iphase I'm not sure of where you are getting your 491.5A from. I just don't know how to go about it. For example, take a 400 V (VLL) three phase system with the following loads: phase 1 = 80 A, phase 2 = 70 A, phase 3 = 82 A, the line to neutral (phase) voltage VLN = 400/√3 = 230 V The kW in your formula is the three phase kW, so I think you should be using 746 (not 249). Also, thanks again for posting and all of your help. Also, if this was a Delta configuration, then the line current would be A-N, B-N and C-N). Please read AddThis Privacy for more information. Similarly for phase B (1/2AB + 1/2BC) and phase C (1/2BC + 1/2AC). Power is related to the voltage and current so regardless of star or delta if the box taking the same power, both voltage and current will be the same. To find the kVA you can use sqrt(kW^2 + kWr^2), where kWr is the reactive power. It works the same a for a consumer of power. Cheers, Nathan. Basic Formula to Calculate Apparent Power in Single and Three Phase Circuits EE. Power factor (cosΦ). phase 3 apparent power = 82 x 230 = 18,860 VA = 18.86 kVA Three-phase Rectification. What I need to know is how many amps I'm pulling on each individual leg. kVA = kW / power factor = 12/0.86 = 13.9 kW (13900 W) So it is the second part of your reply that I don't understand. Typical power factor values. So, VD = 1.732 x 21.2 x 100 x 80/83,690 = 3.51 Voltage Drop Example 3 — Find the size of copper wire needed in a single-phase application to carry a load of 40 amperes at 240 volts a distance of 500 feet with a 2% voltage drop. Normalized waveforms of the instantaneous voltages in a three-phase system in one cycle with time increasing to the right. If you interested in an introduction you can view our post: Network Theory – Introduction and Review. kVA per phase = kW per phase / power factor *Line-to line voltage values to be considered. Most AC power today is produced and distributed as three-phase power where three sinusoidal voltages are generated out of phase with each other. In general when connecting in delta you have a higher voltage on each leg, so I would say you consume more power. If you don't have a power factor use 0.9. L = Length of the circuit from power supply to load. I = 249/(1.73*0.72*380) = 0.52 A By writing an electrical note, you will be educating our users and at the same time promoting your expertise within the engineering community. The voltage drop formula for 3 phase systems is the following: where: VD = The voltage drop of the circuit, in volts. tian, There is always more than one way to do things. Voltage drop formulas. This calculation applicable for both the primary and secondary winding of a transformer. L = Length of the circuit from power supply to load. The Average-Value Rectifier (Three-Phase) block models an average-value, full-wave, six-pulse rectifier. Voltage drop E VD = IR cosθ + IX sinθ where abbreviations are same as below “Exact Method”. Please check it .if u divide kw by p.f u will get kVA not KW. Formula : Three Phase Electric Power = V * I * 1.732 * PF Where , V = Voltage I = Current PF = Power Factor (0.8) Three Phase Electric Power calculation is made easier here using this online electrical calculator. Dear jcdelao, Using the formula, [Sqrt3 x V x I x Cos (Phi)= Power (Watts)] , the current comes to be about 711 A. The three phase power calculator calculates the active and reactive power current from the following parameters: Voltage (V): Enter the phase-to-phase (\(V_{LL}\)) voltage for a 3-phase AC supply in volts. I work in the entertainment industry and definitely work with a star connected (wye) system where all legs measured to neutral is 120V and leg to leg is 208V. I just went through and got a few strange results, and realised that earlier you state VLL = √3 x VLN Hence I wondered why you would then multiply VLL again by √3. Current I = kVA per phase / phase voltage I have a small 400 V three phase 4 wire (star) installation with the following resistive loads on each; I need to calculate the line current in each of the three phases can some one please help with a formula? The power factor is the ratio of the real work to the apparent power. You give the worse case as 80.6A. If you want to promote your products or services in the Engineering ToolBox - please use Google Adwords. = kW / (3 x pf) divided by (VLL/√3) This configuration of voltage sources is characterized by a common connection point joining one side of each source. What is the difference between the two. Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro .Add the Engineering ToolBox extension to your SketchUp from the SketchUp Pro Sketchup Extension Warehouse! Calculating Currents in a Balanced Three Phase Delta Circuit –General ..... 23 4D.1 Resistive Loads ..... 23 4D.2 Capacitive Loads..... 27 4D.3 Inductive Loads..... 29 4D.4 Two or More Loads ..... 31 4E. Kindly show the computation. Phase B starts at 0 at 120 degrees and Phase C starts at 0 at 240 degrees. In the post, the motor is a three phase load, where as the socket is single phase - in each case case you have the line current which is common (for example, the current flowing in L1). Also be aware that if draw more power, you equipment may not have been designed for it. I do have my 'Motor Starting - Star Delta' post drafted which explains this in more detail. AddThis use cookies for handling links to social media. The voltage drop formula for 3 phase systems is the following: where: VD = The voltage drop of the circuit, in volts. Thanks. I will also put together a proper answer when I get some time. Generally when people talk about power factor, they are concerned with the overall system. The Three-Phase Voltage System Three-phase voltage systems are composed of … tanθ=Q/P, Hi all, i have problem in total current computation from ;three phase and single phase, the system is 380v 3-phase, line to neutral is 220. i computed the current from line to neutral AN=80.6, BN= 65.8, CN=73.2a three phase current is 491.5a. As an example, consider a loa… If you also know the power factor you can convert between kVA and kW as shown earlier. Voltage Drop - Generally we take the percentage of voltage drop and the most common percentage of voltage drop is 3 percent and 5 percent. V Rated is the rated AC voltage that you specify on the block mask.. P fixed is the fixed power loss that you specify on the block mask.. R fixed is the fixed per-phase series resistance in an equivalent wye-connected load.. i p, i n are the currents flowing into the positive and negative terminals of the rectifier. Add up the three phases = 48720 VA (or 48.72 kVA). Phase A starts at 0 at 0 degree phase angle, rises to 1 at 90 degrees, back to 0 at 180, to -1 at 270 degrees, and back to 1 at 360 degrees. The motor would be running faster due to the frequency. Need your excellent advise Mr. Steven. When I try to remember formulae I always forget them soon or become unsure if I am remembering them correctly. Three-phase electric power is a common method of alternating current electric power generation, transmission, and distribution. It is important that calculations be carried... A lot of our members work in countries where PPE (personal protective equipment) is regulated or they work for companies/organizations which take employee... Modelica is an open source (free) software language for modelling complex systems. THREE-PHASE CIRCUIT CALCULATIONS In the following examples, values of line and phase voltage, line and phase current, … so that i can assign suitable cable and breaker? May 28, 2018 Basic Formulas, Apparent power is defined as the product of current time voltage passing through an AC circuit. Hi Steven, Thanks for sharing your knowledge, it really helped me understanding the theory. I would say you cannot use the motor at 50Hz, 380V. 345/380 = 0.90 I Phase Similar method for the other phases. The power taken by a circuit (single or three phase) is measured in watts W (or kW). The simple formula to calculate the rating of three phase Transformers is: KVA = (√3. Steven, let me give you a few more details. To get started and understand our policy, you can read our How to Write an Electrical Note. This post about the 3 phase motor current calculation formula explanation. Line to line voltage: W applied = 3 1/2 U ll I cos Φ = 3 1/2 U ll I PF (1) where. Power & Amp - The amount of voltage running through the lines is related to the power and amp. You can calculated this be summing the A, B and C phases, taking into account the phase difference (easiest to do this using complex notation). I believe that as you lower the voltage across the lamp, the current would reduce and the brightness (think of the lamp as a resistance). This video is about 3 phase motor amps calculation Or 3 phase motor current calculation guide. Hi Steven, how to get the total KVA of the system if Line AB =642.24amp. Network analysis is not the intent of this note. The new posting/commenting system is way better than the current one and I'm now just waiting to use it. Basic Formula to Calculate Apparent Power in Single and Three Phase Circuits EE. With A-B, B-C and A-C you are looking a loads in a delta connected system. The key to doing this is that the sum of power in each phase is equal to the total power of the system. thank you very much. Each phase is a sine wave. ... Voltage drops are phase-to-phase, for three-phase, three-wire or three-phase, four-wire 60 Hz circuits. Enter the power factor of the load. Back to basic, below are the simple Electric Power formulas for Single Phase AC Circuit, Three Phase AC Circuits and DC Circuits. Phase A starts at 0 at 0 degree phase angle, rises to 1 at 90 degrees, back to 0 at 180, to -1 at 270 degrees, and back to 1 at 360 degrees. Similarly given the power in each phase you could easily find the phase currents. It is a type of polyphase system and is the most common method used by electrical grids worldwide to transfer power. I am calculating the current in a 3 phase 380 V balanced Y system with a single motor load of 746 watts with a power factor of 0.72 and am getting different results when using the approaches suggested above. Where I have issues is when we have loads connected across two phases. The relationship between kVA and kW is the power factor (pf):Single phase system - this is the easiest to deal with. Line and Phase currents are related to each other as: I_line=square_root(3)*I_phase Which means that whatever supply current we have, we need a wire cross-section for 1/ square_root(3) times line current only. The calculation of current in a three phase system has been brought up on our site feedback and is a discussion I seem to get involved in every now and again. The product of the voltage and current is the apparent power and measured in VA (or kVA) . IEC 61439 'Low-voltage switchgear and controlgear assemblies', specifies standard arrangements of switchboard (call forms of internal separation). The voltage measured between any line and neutral is called phase voltage. Most AC power today is produced and distributed as three-phase power where three sinusoidal voltages are generated out of phase with each other. CM = Circular-Mils (conductor wire gauge) Notes: • The National … VA is simply the current times the voltage, so knowing this and the voltage can give the current. For Example :- Each phase of 3 phase machine takes a load of 16 amps, So how do I calculate how many KVA generator is required ? If the 491.5A is an existing or additional loads to the 80.6A, you would need to add to get the total current (i.e. These applications will - due to browser restrictions - send data between your browser and our server. KW, KVA KW is real consumed power turned into heat, and is the product of volts x current x power factor. dilan, the kVA would be ( 642.24 + 651.85 + 651.84) * 220 = 428102 VA = 428.1 kVA the kW would be 428.1 x 0.86 = 368.2 kW For the breaker, I would likely be looking at 800 A (posibly something like a MasterPact NT or NW, depending on other parameters) and setting the overload protection in the range of 710 A (this is plus 10%). I line = 0.90 * 1.73 = 1.57 A For each phase the VA is current x voltage (i.e. Here is a 3 phase generator output voltage formula to calculate the three phase generator output voltage. Open 3-Phase Circuit Formulas: Open Delta Watts = 2 / 3 W DELTA Open Wye Watts = 1 / 2 W WYE Open 4-wire Wye Watts = 2 / 3 W WYE. Ignoring efficiency and assuming single phase 230 V, the VA would be 184 (230 V x 0.8 A) and power factor 110/184 = 0.6. Also make sure you use the larger voltage of the system voltages, ex) if   P 1ph = P 3, Single phase apparent power S1ph (VA):      ie 10mm cable carrying 50A 3 phase over 30m VD=3.8x50x30 / 1000 = 5.7V or VD=3.8x150x30 / 1000 = 17.1V I think it has to be the first but am a bit mixed up, need to brush up on some 3 phase theory I think. For 3 Phase 3 Wire system. Try to look at the following post. And now I would like to know how does the calculation works when a generator has to be used? For the cable size I'll refer you to our calculator as it depends very much on the type of cable and installation: http://myelectrical.com/tools/cable-sizing-calculator After looking at the cable size calculator, if you have any questions on using it (or questions on the breaker selection), you can ask in the questions section of the site: hi,i would like to ask if getting the current in any configuration (delta or star) is it always the power in kva to be used?.i always had some trouble in this.pls help. Your California Privacy Rights Sorry, your blog cannot share posts by email. We previously studied that voltage is the basic property of electrical circuits . If  I have a system having Amperes on each phase as 80A, 70A, 82A and VLL is 400V and VLN is 210 V. Kindly share how to calculate its power consumption in KVA. Now the calculation you gave me gives me the total amps on A-B but it doesn't tell me how many amps I'm pulling on A and how many amps I'm pulling on B. I know when you are dealing with loads connected across phases figuring out the current isn't as straight forward as using ohms law. Kindly I want to know in 3 phase distribution ( example a house), Say I have 29 kVA ... equals to 36,250watts  (PF=0.8). Again, assuming equal power ratings of the three single-phase AC sources, the total power available to a connected 3-phase AC load is the product of the 3-phase AC line voltage times the 3-phase AC line current multiplied by the √3. Where: V is the voltage (volts) and I is the current (amps). So (I) would be equal to 72.79A ... is this 72.79 divided by the 3 phase, i.e does each phase has a load of 24.26 A ? alternating-current-circuits Have a read of the note and if you are still unclear, you can add a comment to post. I know this probably is easy to understand, but I got myself to a completely confused state. And the value of the impedance and the reactance if required. You can easily find electric power in watts by using the following electric power formulas in electric circuits. To me the easiest way to solve three phase problems is to convert them to a single phase problem. I = Amps. Mathematical calculation for KVA and MVA for transformer. Let’s see two most common methods for calculation of voltage drop – approximate and exact methods: 1. The current is simply the kVA divided by the voltage. Voltage drop formulas. now simply follow the above single phase method. If you do a site search for "International Voltages" we have a Wiki page which lists some of these (may be slightly out of date). Power (3-phase) = kW, therefore per phase = kW/3 To make the situation confusing, the contractor got the confirmation from the manufacturere. Hope this makes some sense. The single- phase voltages are phase to neutral voltages. Three phase simply means you have three windings instead of one; giving you the A, B and C phases (and if star connected a neutral conductor).   I= S 1ph V LN = P 3×pf 3 V LL, Simplifying (and with 3 = √3 x √3):      You can target the Engineering ToolBox by using AdWords Managed Placements. Working with single phase, three-phase and DC (direct current circuits) and you quickly need to reference formulas for voltage drops and power calculations for a given conductor? Single-phase three-wire: Also known as Edison system, divided or neutral phase with central intake. You could do the calculation in terms of peak current if you wanted (for a sine wave the relationship between the peak and RMS is the square root of two). Enter the rated volts, amps, power, and efficiency to find the current flowing through the motor. The following formula calculates total power in a three-phase system based on KW and KVAr or voltage and current. Motor rated power is normally the output power, so to be fully accurate you need to consider the efficiency. unbalanced phase shift), then it is necessary to revert to more traditional network analysis. To avoid any misunderstanding, the following post may also help you: http://myelectrical.com/notes/entryid/172/three-phase-power-simplified. The line current is then the kVA divided by the voltage, i.e. The 3 phase load current amps formula is explain with a three phase load voltage induction motor nameplate data. At the fault location, because the phases are shorted, they will be at nearly the same voltage (close to zero depending on the impedance). Back to basic, below are the simple Electric Power formulas for Single Phase AC Circuit, Three Phase AC Circuits and DC Circuits. However, if you prefer you can write, manage... GE's latest thinking on product manufacturing is he Shingijutsu philosophy or Lean production system. Our software is the only cloud-based solution and has been built from the ground up to be fully responsive - meaning you can access your cables from anywhere and on any device, desktop, tablet or smartphone. 21,000 / 230 = 91 A. 2 thoughts on “ Cable Sizing & Voltage Drop Calculations Formula ” Brian July 19, 2019. Single phase to 3 phase power calculation input requirement = The square root of 3 (1.732) x 10 amps = 1.732 x 10 amps = 17.32 Amps. Voltage Drop formula for Single Phase and DC Circuits . I have 3 loads on each phase as L1-2=19.74 VA, L2-3=16.91 VA L1-3=13.81 VA Please tell the capacity of the transformer required. The same definition holds for both three phase and single phase systems. Voltages in Three Phase Circuits - General ..... 18 4B. 380/1.73 = 219 V Line-Neutral (Phase Voltage) How to use the formula and which formula to find it out..??? Easy enough. Balanced three phase system with total power P (W), power factor pf and line to line voltage VLL, Convert to single phase problem:      The Three-Phase Voltage System Three-phase voltage systems are composed of three sinusoidal voltages of equal magnitude, equal frequency and separated by 120 degrees.