I would say you cannot use the motor at 50Hz, V. The motor would be running faster due to the frequency. In addition the voltage would be increase the torque and current for which the motor is likely not designed. I have the same issue with our Contractor supplying pump motor 50hz, where-in our system here is 60 hz.
To make the situation confusing, the contractor got the confirmation from the manufacturere. ABB that according to their calculation, that 50hz motor would be fine for 60hz system. Need your excellent advise Mr. Thank you so much! I deal with unbalanced systems on a frequent basis and am trying to figure out how to calculate the amps drawn on each leg.
Strictly speaking you should be using kVA which you can obtain by dividing the watts by the power factor. Also make sure you are really dealing with a delta system and not a star-connected system i. Steven, let me give you a few more details.
I work in the entertainment industry and definitely work with a star connected wye system where all legs measured to neutral is V and leg to leg is V. What I need to know is how many amps I'm pulling on each individual leg. We have a lot of loads that are connected line-neutral and figuring out those loads is easy.
Where I have issues is when we have loads connected across two phases. If the system is perfectly balanced I again have no issues figuring out the amps drawn on each leg.
But in the example I gave you the loads are quite obviously not balanced. 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.
I just don't know how to go about it. I understand a little more now perhaps not fully. I think you can still convert to three single phase problems, with phase A having halt of the AB load and half of the AC load.
Thanks for the write up. In your example where you break down a 3-phase problem to a single phase problem with the 36kW load, you get 60A. That 60A is total rms current for a single phase, not the peak current, correct? So is it as simple as multiply by 3 to get the total, 3-phase rms current? Your correct it is the RMS current. 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.
You do not need to multiply by 3. The current calculated is the line current - if you place an ammeter in the circuit, this is what you will measure. So it is the second part of your reply that I don't understand. 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?
If I was to create a 3 phase fault by shorting all three phases together, how much current would go through the fault towards the load? Also, thanks again for posting and all of your help.
Try to look at the following post. 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. If you create a fault the current will increase you have reduced the circuit impedance with the fault. Current won't flow through the fault to the load or very little will.
At the fault location, because the phases are shorted, they will be at nearly the same voltage close to zero depending on the impedance. The load sees this voltage and no current will flow. Hope this makes sense. For a three phase AC generator. Hi all, i have problem in total current computation from ;three phase and single phase, the system is v 3-phase, line to neutral is The three phase current as you are trying to calculate it does not exist.
In the A phase you have You still have your three phase system, with the current in each line being slightly different if all the line currents were the same it would just be a balanced three system. Because you have an unbalanced system, you will have some current in the neural line.
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. 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. In a single phase system you would only have one winding, giving you a single phase live and neutral. Hope this makes some sense. You give the worse case as I'm not sure of where you are getting your If the This is done all the time fridge or toilet extract fan in your house for example.
Just try to balance your single phase loads as much as possible across all three phases. Power factor 0. Kindly show the computation. I like to use kVA as this is just the voltage multiplied by the current. If you know the kVA and voltage, it is very easy to work out the current. If you wanted to do all your calculations in kW, you could - but you would need to include the power factor as well in any calculation.
Thanks Steven, it helps a lot. But if you don't mind, I would like to ask a few more question about the apparent power and complex power. What is the difference between the two. I have a book here about circuits it tells that the key to solving problems about three phase is to find the current. I know that it is right but how can i used it to find the value of complex power?? And the value of the impedance and the reactance if required.
The following note touches briefly on the topic of complex power: 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. Thank you! In general when connecting in delta you have a higher voltage on each leg, so I would say you consume more power. I try not to think like that as it confuses me as well and there is sometimes more to it than that.
My advice would be to look at your actual situation and analysis it to see the effect of changing from star to delta. Also be aware that if draw more power, you equipment may not have been designed for it. Sir, when a voltage dip occurs current increases, so instead of dimming, a bulb should glow brighter but the reverse thing happens, why?
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. Hi Steven, I drive a centrifugal water pump with a three phase motor. I measure the Power kW required by the electrical motor.
I expect it to stay the same. Am I correct? Hi Steven, Thanks for sharing your knowledge, it really helped me understanding the theory. And now I would like to know how does the calculation works when a generator has to be used?
Does Power Factors plays any role? It works the same a for a consumer of power. Just multiply the current by the phase-neutral voltage to get the power per phase and then by 3. The power factor only comes into play if you want to see the kW just multiply the kVA by the power factor. Hi steven sir, I want to know in motors we use capacitor, we use star connection for starting 3 phase, is it because the current lags the voltage by 90 degree in an coil or is it for a different reason..
Regards Abdulla. Sorry if this is a simple question. What is the difference between three phase power factor and single phase power factor. The power factor is the ratio of the real work to the apparent power. The same definition holds for both three phase and single phase systems.
Generally when people talk about power factor, they are concerned with the overall system. If you are looking at it on a phase by phase you may need to be a little careful. Thank you. Assuming V is Line Voltage and load is balanced. There are a lot of interesting two page type notes on various medium voltage topics — switchgear, circuit breakers, bus systems etc.
It is on the Siemens These lifts were first built in by J. Hall and called a paternoster "Our Father", the first two words of the Lord's Prayer in Latin due to its A fundamental concept behind the operation of alternating current systems is that voltage and current waveforms will be sinusoidal — a Sine Wave. Straight forward list of some common motor faults. If I have missed any other common faults, please take a bit of time to add them in as a comment below Kept looking at it. Welcome back Bottle.
Gods below welcome home. Electrical engineering has a multitude of laws and theorems. It is fair to say the Ohm's Law is one of the more widely known; it not the most known.
IEC is the International Electrotechnical Commission's international standard on conductors of insulated cables. Among other things, it defines a Most installations involve some form of lightning protection system which is connected to an earth electrode. The function of the earth electrode is to Lead acid batteries are cost effect and reliable, making them suitable for many applications.
This note examines topics of interest associated with the In particular If you have some expert knowledge or experience, why not consider sharing this with our community. By writing an electrical note, you will be educating our users and at the same time promoting your expertise within the engineering community. To get started and understand our policy, you can read our How to Write an Electrical Note. Loading, please wait.
Steven McFadyen Steven has over twenty five years experience working on some of the largest construction projects. About the author myElectrical Engineering.
View 60 Comments old system. Faiz Ahmad says:. Steven says:. The current flow in the transmission line interacts with the other parameter, i. We know that when current flow within a conductor, magnetic flux is set up. This induced emf is represented by the parameter known as inductance. The flux linking with the conductor consist of two parts, namely, the internal flux and the external flux.
The internal flux is induced due to the current flow in the conductor. The external flux produced around the conductor is due to its own current and the current of the other conductors place around it. The total inductance of the conductor is determined by the calculation of the internal and external flux. Considered a single phase line consisting of two conductors phase and neutral a and b of equal radius r. They are situated at a distance D meters. The cross sections of conductors are shown in the diagram below.
Let the current flow in the conductors are opposite in direction so that one becomes return path for the other. Inductance per conductor. Inductance of both the conductors is given by the formula. The inductance of an individual conductor is one-half of the total inductance of a two-wire line. In symmetrical three-phase line, all the conductors are placed at the corners of the equilateral triangle. Such an arrangement of conductors is also referred to as equilateral spacing. It is shown in the diagram below.
Let the spacing between the conductors be D and the radius of each conductor, r.
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