How to calculate the unbalanced neutral current in a 3 phase circuit
Enter the current drawn in all three-phases. You can note down the current flowing through each phase from Multi-function meter located on your panel. Another option is, you can individually measure current in each phase with the help of clamp-on meter. How to find neutral current? You can also use below formula to find neutral current. How to Calculate Neutral Currents. Step 1. Note the neutral formula. If A, B and C are the three phase currents, the formula to find the neutral current is the square root of the Step 2. Step 3. Step 4.
The power taken by a circuit single or three phase is measured in phasd W or kW. The product of the voltage and current is the apparent power and measured what type of paint to use on concrete basement floor VA or kVA. The relationship between kVA and kW is the power factor pf :. Given the kW and power factor the kVA can be easily worked out.
The current is simply the kVA divided by the voltage. As how to calculate neutral current in 3 phase example, consider a load consuming 23 kW of power at V and a power factor pjase 0. To convert from VA to kVA just divide by The main difference between a three phase system and a single phase system is the voltage.
Take a three phase motor with three windings, each identical consuming a given kW. The kW per winding single phase has to be the total divided by 3. Similarly a transformer with three windings, each identical supplying a given kVA will have each winding supplying a third of the total power.
To convert a three phase too to a single phase problem take the total kW or kVA and divide by three. As an example, consider a balanced three phase load consuming 36 kW at a power factor of 0. Easy enough. To find the power given current, multiply by the voltage and then the power factor to convert to W. For a three phase system multiply how to calculate neutral current in 3 phase three neutrl get the total power.
Hpase above deals with balanced three phase systems. That is the current too each phase is the same and each phase delivers or consumes the same amount of power. This is typical of power transmission systems, electrical motors and similar types of equipment. Often where single phase loads are involved, residential and commercial premises for example, the system can be unbalanced neutra each phase have a different current and delivering or consuming a differing amount of power.
Luckily in practice voltages tend to be fixed or very by only small amounts. In this situation and with a little thought it is possible to extend the above type of calculation to unbalanced current three phase systems. The key to doing this is that the sum of power in each phase is equal to the total power of the system.
Similarly given the power in each phase you could easily find the phase currents. If you also know the power factor you can convert currennt kVA and kW as shown earlier. If the voltages become unbalanced or there are other considerations i. Noting that no overload is permitted. Long-haul durability due to what is a foreword in a book with examples components and wet-type cylinder liners could exceed Residential uses include back up the neuhral you can trust for solar and cjrrent energy.
For commercial businesses, our diesel generators are perfect for food vans, Perkins engines in the Kingdom are known for their good reputation, Please click here if you are not redirected within a few seconds. Three Phase Current — Calculation. Three phase system The main difference phaes a three what is an oil derrick system and a single phase system is the voltage.
Unbalanced Three Phase Systems The above deals with balanced three phase systems. Balanced Voltages Luckily in practice voltages tend to be fixed or very by only small amounts. Unbalanced Voltages If the voltages become unbalanced or there are other considerations i. How to know the right generator for you if you have already calculated the total actual load Total three phase powernow you can use the following formulas to choose the right hw for you.
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Rule 1) If the three phase currents are equal to one another, then the neutral current is zero. If I1 = I2 = I3 then In = 0A. Rule 2) If one of the phase currents is different (higher or lower) than the others, then the neutral current is equal to the difference. If I1 = I2 = I3+/- X then In = X. Mar 16, · the line to neutral (phase) voltage V LN = /v3 = V phase 1 apparent power = 80 x = 18, VA = kVA phase 2 apparent power = 70 x = 16, VA = kVA phase 3 apparent power = 82 x = 18, VA = kVA Total three phase power = + + = kVA. Similarly given the power in each phase you could easily find the phase currents. Apr 19, · In a 3-wire circuit consisting of two phase conductors and the neutral conductor of a 4-wire, 3-phase, wye-connected system, a common conductor carries approximately the same current as the line-to-neutral load currents of the other conductors and shall be counted when applying the provisions of (B)(3)(a).
We only have 3 phase power in our class. I built a simple circuit with 2 equal loads on 2 seperate phases with a shared grounded conductor. I figured that the current in the grounded conductor in a three phase circuit would not be as low as in a single phase situation, but it would be significantly less than in the 2 hots.
When we measured the currents, the neutral was almost the same as the hots. So does anyone know the formula for calculating the current in the grounded conductor in an unbalanced 3 phase circuit? I went over lots forums and archived forums and couldn't find any thing. I appreciate any help you can give. I kinda like this site Location Iowegia. Location NE Nebraska. Exactly the reason Rick Christopherson Senior Member.
Here is where vector mathematics comes in handy, and something you should be teaching to your students. The sum of these two currents in the neutral will be found by adding the vectors. In this case, I chose to use the parallelogram method because it shows better in a single diagram. The other method is to redraw the vectors head-to-tail.
Don't ever let someone here tell you that tail-to-tail vectors means they should be subtracted. That is inappropriate vector math. Besoeker Senior Member. Location UK. Location Massachusetts. Besoeker said:. That is fine where load power factor is identical on all three phases. But not if the power factors differ. That is certainly a fact, but in any electricians training and testing I have seen they are looking for what posted. They don't usally consider PF in the questions involving neutral current.
Location 3 Hr 2 Min from Winged Horses. I'm sure what you say is correct. But it's a bit of a shame, I think. By all means give the expression that posted but with the caveat that it applies to very specific circumstances, not all. Even not most. Nah, on reflection, I don't think it should be taught to electricians. Is it of any practical use? For the simple example I gave, the neutral current is nearly three times the magnitude that you would get by evaluating that expression.
Big Thanks! Thank you all for your great responses. I teach what's called a "pre apprentice" program at the san Diego Job Corps so a lot of your responses are way beyond my students and me too. I think the Vector math that Rick submitted will be really helpful. Thanks again. I'll be BACK! I have no problem with teaching someone the basic formulas, then also informing them that things like power factor and harmonic currents can complicate what is really there.
For the average installer or basic troubleshooting person, that is what they need to know. If they get into a situation where that additional information they can turn to the books or places like this forum for help. Kind of what I do myself as I do not run into power factor or harmonic problems frequently enough to remember formulas, or even some of the technicalities that apply. Just knowing Ohms law, Kirchoff's laws gets most average installers and troubleshooters through what they run into the most.
Knowing what else may be lurking and where to go for more help with it is important though. Location Ohio. Er fellas To the mystery mod who deleted my posts, I was not bickering. I was correcting some misinformation in other posts.