3 phase voltage calculation formula

Single phase power input in this instance is 17.32 Amps. To calculate the voltage output, multiply the number of turns with the area of coil on the armature. Calculation of Power in a Balanced Three Phase Circuit ..... 20 4C. By writing an electrical note, you will be educating our users and at the same time promoting your expertise within the engineering community. With single-phase AC power there is only one single sinusoidal voltage. Similarly given the power in each phase you could easily find the phase currents. NEC 430-150, 10 HP @ 460V, 3 phase I = 14 Amp 3. I would say you cannot use the motor at 50Hz, 380V. The National Electrical Code states that the voltage drop of a feeder circuit must not exceed 5%, and the voltage drop of a branch circuit must not exceed 3%. alternating-current-circuits Have a read of the note and if you are still unclear, you can add a comment to post. Turns Ratio = N 1 / N 2 = V 1 / V 2 = I 2 / I 1. I'm not sure of where you are getting your 491.5A from. The simple formula to calculate the rating of three phase Transformers is: KVA = (√3. In your example where you break down a 3-phase problem to a single phase problem with the 36kW load, you get 60A. The key to doing this is that the sum of power in each phase is equal to the total power of the system. If you also know the power factor you can convert between kVA and kW as shown earlier. To protect the windings of a transformer against overcurrent, use the percentages listed in Table 450.3(B) and its applicable notes. To avoid any misunderstanding, the following post may also help you: http://myelectrical.com/notes/entryid/172/three-phase-power-simplified. While some colleagues prefer to remember formulas or factors, I prefer to resolve the problem step by step using basic principles. Thanks. 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. 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. Consider the motor as a black box taking some power. In Delta connection, phase sides are connected in a cyclical arrangement in order to make a closed loop as shown in figure 1. Sorry if this is a simple question. You can calculate the line current of a transformer by using the appropriate formula for single-phase or 3-phase systems: Single-phase: I = VA ÷ E. 3-phase: I = VA ÷ (E × 1.732) Overcurrent protection. You can't divide the current by three (power kW or kVA - yes). Network analysis is not the intent of this note. Voltage Drop Calculations shall be provided in accordance with the NEC, regardless of where the cable was manufactured. This configuration of voltage sources is characterized by a common connection point joining one side of each source. Project management and team collaboration, with clear easy to read calculations and reports. Basic Formula to Calculate Apparent Power in Single and Three Phase Circuits EE. Then multiply the DC magnetic field with the square root of 3. I have the same issue with our Contractor supplying pump motor 50hz, where-in our system here is 60 hz. And now I would like to know how does the calculation works when a generator has to be used? 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? If you create a fault the current will increase (you have reduced the circuit impedance with the fault). I just don't know how to go about it. I deal with unbalanced systems on a frequent basis and am trying to figure out how to calculate the amps drawn on each leg. 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. V Line-Line = 380 V V P = Phase Voltage V L = Line Voltage I P = Phase Current I L = Line Current R = R1 = R2 = R3 = Resistance of each branch W = Wattage Wye and Delta Equivalent W DELTA = 3 W WYE. now follow the above single phase method 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? 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). That definitely clarifies the error in my calcs. Also make sure you use the larger voltage of the system voltages, ex) if It works the same a for a consumer of power. This configuration of voltage sources is characterized by a common connection point joining one side of each source. To me it is easier, and if necessary I can always derive the formulae. Voltage Drop Formulas and Calculation. This post about the 3 phase motor current calculation formula explanation. U.S Formula (NEC) For three phase: VD = 1.732 x L x R x I / 1000 For single phase: VD = 2 x L x R x I / 1000 VD: The voltage drop (V) L : The length of conductor (m) R: The impedance value from NEC Chapter 9, Table 9 (ohm/km). 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. Please read AddThis Privacy for more information. I understand a little more now (perhaps not fully). 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. Once you know the kVA, you can calculate the power factor form pf=kW/kVA. The current just does not work that way. For example my current system has the following power draw: A-B 56,000 Watts B-C 23,000 Watts A-C 17,000 Watts It's hooked to a 3 phase wye system 208/120. In Delta connection, phase sides are connected in a cyclical arrangement in order to make a closed loop as shown in figure 1. The kW per winding (single phase) has to be the total divided by 3. Divide kW by the power factor to get the kVA. Let’s see two most common methods for calculation of voltage drop – approximate and exact methods: 1. Power (3-phase) = kW, therefore per phase = kW/3 Exact method #1. Solution: Kilo-volt-ampere = (8 x 5 x 1.732) / 1000 = 0.06928 kVA. Voltage drop formulas. 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). The kW in your formula is the three phase kW, so I think you should be using 746 (not 249). 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%). thank you very much for the reply, but how to calculate the total ampere of the system, if A phase 80.6A, B phase 65.8A, C phase 73.2A. This post about the 3 phase motor current calculation formula explanation. However, if you prefer you can write, manage... GE's latest thinking on product manufacturing is he Shingijutsu philosophy or Lean production system. The... Here’s list of some famous scientists. 345/380 = 0.90 I Phase Pip, sorry for the delay – busy relocating countries/jobs at the moment. Total three phase power = 18.4 + 16.1 + 18.86 = 53.36 kVA. Similar method for the other phases. How to use the formula and which formula to find it out..??? Other things to consider while carrying out calculations may include the efficiency of equipment. By using this same procedure but inserting the respective single-phase voltage, you get the following single-phase constants, as shown in Table 1. The line current is then the kVA divided by the voltage, i.e. I = kW / ( √3 x pf x VLL ), in kA Also be aware that if draw more power, you equipment may not have been designed for it. Abiodun Sobayo. And the value of the impedance and the reactance if required. KVA is calculated by multiplying the line to line maximum voltage & maximum phase current; then multiplying this value with 1.732 in case of three phase ; lastly dividing the final value by 1000 for KVA and 100,000 for MVA . I would treat these as three separate single phase problems. Three phase system - The main difference between a three phase system and a single phase system is the voltage. Cos θ = Power Factor: Motors see 6-5, 6-6, .6-.8 is usual see 5-1 to 5-8 for more power factor calculations, also 8-2 Given voltage drop, find wire size Voltage Drop 3∅ = √3 I (Z) L Z = Voltage Drop = Vd √3 I L √3 IL Voltage Drop 1 ∅= 21 (Z) L Z = Voltage Drop = Vd 2 I L 2 IL Procedure (Example) 1. Formula for Voltage | How to calculate Potential Difference. W applied = real power (W, watts) Why is the Y and Delta line current the same? The current is simply the kVA divided by the voltage. To get started and understand our policy, you can read our How to Write an Electrical Note. Just multiply the current by the phase-neutral voltage (to get the power per phase) and then by 3. When making adding a Note to our site we have a great online WYSIWYG editor and things are pretty simple. 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. The power taken by a circuit (single or three phase) is measured in watts W (or kW). You can calculate the line current of a transformer by using the appropriate formula for single-phase or 3-phase systems: Single-phase: I = VA ÷ E. 3-phase: I = VA ÷ (E × 1.732) Overcurrent protection. Thanks Steven! Please check it .if u divide kw by p.f u will get kVA not KW. As far as line and phase currents are concerned, they are related to each other as: Iline=√3IphaseIline=√3Iphase Which means that whatever supply current we have, we will have wire cross-section for 1/√31/√3times line current only. I've always been bad a remembering formulae, so I prefer to remember concepts/methods. one more question. What is the difference between three phase power factor and single phase power factor. BC=651.85A, AC=651.84A, supply voltage 220 line to line. Example 3: The transformer of a small building is 25000VA single-phase, with a voltage of 240V and an impedance of 3%, which will be the short-circuit level of the transformer. When wire length is in feet. Approximate method. To convert from VA to kVA just divide by 1000. Basic Voltage Drop Formula. To me the easiest way to solve three phase problems is to convert them to a single phase problem. Where: V is the voltage (volts) and I is the current (amps). Having never used it before, I thought I would download a development... Electrical engineering is a field that covers a wide variety of sub-fields, including electricity and electronics. Hi Steven, I drive a centrifugal water pump with a three phase motor. Any ideas where I'm going wrong? Calculate three-phase motor power consumption by multiplying amps by volts by the square root of three (W = AV(sqrt 3). In a three phase system we have the line to line voltage (VLL)  and the phase voltage (VLN), related by: or alternatively as: Table 1: Value of voltage factor (c)for calculation of short-circuit current (Source: AS 3851: 1991) Nominal system voltage (U n) Voltage factor (c) Maximum short-circuit current: Minimum short-circuit current ≤ 650 V: 1.06: 0.94 > 650 V: Note:Highest voltage of the system as defined in AS 1824.1. Is this wrong? 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. Steven, let me give you a few more details. 2. Through a circuit, a current of 9A flows through that carries a resistance of 10 $$\Omega$$. Thanks for pointing out the mistake. John, line voltage is dependant on country (and varies within countries). Would it be possible for you to ask this in our question section. The Average-Value Rectifier (Three-Phase) block models an average-value, full-wave, six-pulse rectifier. To make the situation confusing, the contractor got the confirmation from the manufacturere. Balanced three phase system with total power P (W), power factor pf and line to line voltage VLL, Convert to single phase problem:      For the red phase, assuming a power factor of 0.95, the kVA is 20 kW / 0.95 = 21 kVA. When I try to remember formulae I always forget them soon or become unsure if I am remembering them correctly. Phase Voltage = VLL/√3 I like to use kVA as this is just the voltage multiplied by the current. Just try to balance your single phase loads as much as possible across all three phases. The voltage measured between any line and neutral is called phase voltage. Also make sure you are really dealing with a delta system and not a star-connected system (i.e. The voltage drop formula for 3 phase systems is the following: where: VD = The voltage drop of the circuit, in volts. To find the kVA you can use sqrt(kW^2 + kWr^2), where kWr is the reactive power. This is typical of power transmission systems, electrical motors and similar types of equipment. three phase power is 36 kW,  single phase power = 36/3 = 12 kW Single-phase three-wire: Also known as Edison system, divided or neutral phase with central intake. 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. Luckily in practice voltages tend to be fixed or very by only small amounts. I = Amps. Motor rated power is normally the output power, so to be fully accurate you need to consider the efficiency. I pretty sure the formula given is correct. 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. 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. The simple formula to calculate the rating of three phase Transformers is: KVA = (√3. 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 = kW / (√3 x pf x VLL) - your formulae Often where single phase loads are involved, residential and commercial premises for example, the system can be unbalanced with each phase have a different current and delivering or consuming a differing amount of power. Back to basic, below are the simple Electric Power formulas for Single Phase AC Circuit, Three Phase AC Circuits and DC Circuits. Principle. Need your excellent advise Mr. Steven. *Line-to line voltage values to be considered. Generally there are two phases - Single phase or three phase. I know that it is right but how can i used it to find the value of complex power?? my question is do i need to multiply 80.6a to 1.732 to convert in 3 phase? If sending end voltage and load PF are known. If you know the kVA and voltage, it is very easy to work out the current. As an example, consider a loa… You can easily find electric power in watts by using the following electric power formulas in electric circuits. Alternatively add the currents and multiply by the voltage (80+70+82)*210 = 48.72 kVA. Power & Amp - The amount of voltage running through the lines is related to the power and amp. phase 1 apparent power = 80 x 230 = 18,400 VA = 18.4 kVA      This formula can help you determine voltage drop across a circuit, as well as the size wire gauge you will need for your circuit based on the maximum desired voltage drop. KW, KVA KW is real consumed power turned into heat, and is the product of volts x current x power factor. 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). If you don't have a power factor use 0.9. Actually, The calculation of KVA capacity for a Three Phase Transformer is based on Winding Voltage and Amperage information. kVA = kW / power factor = 12/0.86 = 13.9 kW (13900 W) Strictly speaking you should be using kVA (which you can obtain by dividing the watts by the power factor). 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). The reader is encouraged to review AN109, References 3, 4, and 5 as background for this Application Note. I thought Y systems had lower line currents and that was one advantage to using them. In this situation and with a little thought it is possible to extend the above type of calculation to unbalanced current three phase systems. For each phase the VA is current x voltage (i.e. Only emails and answers are saved in our archive. THREE-PHASE CIRCUIT CALCULATIONS In the following examples, values of line and phase voltage, line and phase current, … Here is a 3 phase generator output voltage formula to calculate the three phase generator output voltage. To protect the windings of a transformer against overcurrent, use the percentages listed in Table 450.3(B) and its applicable notes. This figure is a constant found in three phase, as the phases do not generate the same amount of power (simultaneously). At the fault location, because the phases are shorted, they will be at nearly the same voltage (close to zero depending on the impedance). Your correct it is the RMS current. so that i can assign suitable cable and breaker? KVA is apparent power, is always greater than or equal to KW and is the product of volts x amps 1 phase, volts x amps x , √3, 3 phase. The 3 phase Induction motor is popular for its efficiency and is … Because you have an unbalanced system, you will have some current in the neural line. In this tutorial we’re going to be learning more about three phase electricity. I hope to get some answers and if any reference on web would be great. Two phase four wires electric power is the electrical energy consumed by the load from two phases having difference of 1 quarter of a cycle between them. 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. This is done all the time (fridge or toilet extract fan in your house for example).   S 1ph = P 1ph pf = P 3×pf, Phase current I (A) is the single phase apparent power divided by the phase to neutral voltage (and given VLN=VLL / √3):      thanks. Basic Formula to Calculate Apparent Power in Single and Three Phase Circuits EE. Please check this and if you find any errors or mistakes let me know. Power factor 0.86, and what size of breaker and cable should I use. You give the worse case as 80.6A. I will also put together a proper answer when I get some time. The current is simply the kVA divided by the voltage. Am I correct? phase 3 apparent power = 82 x 230 = 18,860 VA = 18.86 kVA But a different result when using Hope this makes sense. So it is the second part of your reply that I don't understand. In the second formula, the phase values of voltage and current are multiplied by 3. 3 phase system, if 1 phase out ( fuse cut0ff burn ) for meter kwh, can make the electricity bill increase..?? For 3-phase systems, we use the following equation: kW = (V × I × PF × 1.732) ÷ 1,000. In a single phase system you would only have one winding, giving you a single phase (live and neutral). Dear jcdelao, Using the formula, [Sqrt3 x V x I x Cos (Phi)= Power (Watts)] , the current comes to be about 711 A. By remembering that a three phase power (kW or kVA) is simply three  times the single phase power, any three phase problem can be simplified. Formula to calculate power, current and voltage in three-phase wiring (unbalanced load, different loads on each of three phases) : Pt=P1+P2+P3 P1=V*I1*cosφ1 I1=P1/(V*cosφ1) Same thing for each phase… V=P1/(I*cosφ1) Pt = total power of the circuit in watt (W) P1, P2, P3 = power of phase 1, phase 2 and phase 3 in watt (W) Thanks for the write up. Voltage Drop Formula for Steel Conduit. Where I have issues is when we have loads connected across two phases. We’ll cover how 3 phases are generated, what a Cycle and Hertz mean, plot the voltage wave form as it’s being generated, calculate our single phase and three phase voltages. Voltage drop E VD = IR cosθ + IX sinθ where abbreviations are same as below “Exact Method”. Also, thanks again for posting and all of your help. System voltages and currents can be found by drawing out the circuit in full detail and using Kirchhoff's laws and other network theorems. We previously studied that voltage is the basic property of electrical circuits . Voltages in Three Phase Circuits - General ..... 18 4B. To convert a  three phase problem to a single phase problem take the total kW (or kVA) and divide by three. If your looking for more detailed information... IEC 60947 is the circuit breaker standard and covers the marking of breakers in detail. 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. It is a type of polyphase system and is the most common method used by electrical grids worldwide to transfer power. I thought it would be good to write how I do these calculations. 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 Within the body of the post I have added an example of how to derive the formulae. Phase B starts at 0 at 120 degrees and Phase C starts at 0 at 240 degrees.   I= S 1ph V LN = P 3×pf 3 V LL, Simplifying (and with 3 = √3 x √3):      ... Voltage drops are phase-to-phase, for three-phase, three-wire or three-phase, four-wire 60 Hz circuits. The three phase calculator may also help you: http://myelectrical.com/tools/3phasecalculations.aspx. I have now changed it to show kVA. V x I) /1000. 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. Given the kW and power factor the kVA can be easily worked out. should i combine/sum phase A, phase B, Phase C and 491.5A. From this post learn complete about how to calculate the load current of 3 phase motor. The power P in kilowatts (kW) is equal to 3 times the power factor PF times the phase current I in amps (A), times the line to neutral RMS voltage V L-N in volts (V) divided by 1000: P (kW) = 3 × PF × I (A) × V L-N (V) / 1000. Try to look at the following post. With single-phase AC power there is only one single sinusoidal voltage. If the voltage supplied from the grid changes within acceptable tolerances, say 5%, what would you expect will happen to the Power (kW) which I measure?. can i connect single phase motors to line-neutral?like air compressor & pump motor? So is it as simple as multiply by 3 to get the total, 3-phase rms current? 3 Phase Induction Motor current calculator is used to calculate the rated and full load amperes of the motor. Current = W / voltage = 13900/230 = 60 A. That is the current in each phase is the same and each phase delivers or consumes the same amount of power.