# Questions tagged [three-phase]

AC power with three legs run 120 degrees out of phase

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### Can I share a 3-phase motor branch with a small single phase load?

I have a 15hp 3-phase motor on a 50A 120/208 wye circuit. I also have a small 1A dc motor with controller and some monitoring circuits - this secondary system needs 24vdc and 1.5A altogether. I ...
459 views

### why we say that in three phase system total power delivered to the balanced three-phase circuit is the same at any instant

My question is: why we say that in three phase system total power delivered to the balanced three-phase circuit is the same at any instant?. This is how I understood that one phase at one point of ...
201 views

### Power consumed by the Resistive load

I am really confused with the above problem. I can also solve the problem taking an AC supply across a 20ohm resistor and end up getting like P = 100^2/20 = 500W I am not able to digest the solution ...
440 views

### Three phase converter - capacitor switching

I've started building a single to three phase converter. My research started with the likes of this paper. I've set a bank of 40uf/440v capacitors up and a potential relay. The relay is a Supco SUPR. ...
195 views

### Converting 110v at 8.5 amps to 208 three phase amperage [closed]

I have some equipment that uses 8.5 amps and 1050 watts on a 110v. Any idea what the amperage would be on 208 three phase?
4k views

### Is it possible for 220V to have three phases? [closed]

So, is it possible/does it exist that 220V has three phases?
987 views

### Problem with BLDC motor drive using PWM

We are trying to speed control a BLDC 48V 500W hub motor using hall sensors. We are using IRF540N MOSFETs with IR2112 gate drivers and Arduino as MCU. We implemented the 3 phase inverter and in ...
1k views

### Single-Phase-to-Ground Fault doubts

I'm studying Fault Analysis Using Symmetrical Components and I have doubt over the single Phase to Ground Fault. On the book is written that generally Is and It are equal to 0 during a single-phase ...
343 views

### convert 48vDC into 230vAC 3phase [duplicate]

From a battery bank of 48VDC I would like to power 3 230vAC 3ph 10hp motors to power a large vessel. Would 2 10kW inverters work for this? Below is the what I envision. VFDs would feed into motors ...
58 views

### Unbalanced Fault Problem

I have attached the image of a theoretical question with its explanation given in my book. can anyone please explain this ? I am not able to start from anywhere so I can't show my work. I am posting ...
21k views

### How to connect a three-phase motor

I am trying to fix an old three-phase drill. The motor has 3 wires coming out of it, which connect to the three phases. Connecting it to the power does nothing, and so I tested it with a multimeter, ...
160 views

### Generated current in a $3\times450$ VAC $60$ Hz $1150$ kVA generator

Let's say I've a $3\times450$ VAC $60$ Hz $1150$ kVA generator. How much current will there be generated when it runs at maximum capacity? MY WORK: The total Active power over a three-fase ...
241 views

### Balanced star 3ph system

I have balanced star three phase generator 380V with junction point is connected to ground And current through from junction point to ground is I0=0 for that clearly say it is balanced system when i ...
71 views

### Net-Zero Magnetic Fields in a Three-Phase Motor

When a three phase motor in running and you clamp an amp-meter around all three of the phase wires, you should expect to read zero because the magnetic fields cancel each other out. I'm having ...
229 views

### mmf distribution in rotating electrical machines

we have known in ABC sequence in three phase system,phaseA leads phaseB by 120 electrical degrees, but in mmf vector of electrical machines,mmf vector of phaseB leads mmf vector of phaseA by 120 ...
155 views

### Feeding energy to the power grid

I am doing a research about the electricity grid and a marketplace where neighbours can trade energy with each other. I found out if your PV cell has excess energy you can with an inverter put it ...
63 views

### 3 phase line operating via 3 one phase relay

I want to operate a 3 phase 10Hp motor pump. I have a 3 phase electric line, but due to some requirements, I have to operate each line (A-B-C) in 3 phase using 1 phase relay separately. My question ...
74 views

### Non equal phase currents at nominal speed vector control Permanent magnet synchronous motor

I working on my implementation of vector control for PMSM. I'm having close loops over speed, current in d axis(flux loop), current in q axis(torque loop). I'm using MATLAB/Simulink for vector control ...
50 views

### Measuring direction of a three phase motor (400VAC, 50 Hz) within a 5V-circuit

I've got a lot of motor controller boards, without the actual motor, and I'm interested in measuring at the output terminals (U,V, W) to see if there's any voltage. This to just check rudimentally if ...
65 views

### How to compensate for grid quality changes in three phase power

Suppose I measure both current and voltage going to an electric motor. So that I have two continuous streams of three phase data (current and voltage). I want to use this data to diagnose potential ...
2k views

### Is there a convention for the ordering of phases in three-phase power in the US?

I recently moved my small machine shop to a new location. Both locations had 3-phase power, and I wired up a 3-phase air compressor in both locations. In both locations, I used the convention of ...
52k views

### Australian 3-Phase Colour Code Standard

We're ordering some machinery from China and need it manufactured to Australian electrical standards including the wiring colour code. Unfortunately we don't have any electricians or engineers that ...
35 views

### Calulating the total thermal power in three phase system

In my book I have following task that actually has a solution. However I do not understand the solution idea and that's why I'm asking you guys to help me understand that if possible. Why I do not ...
753 views

### Simulate isolation transformer in LTspice

Hi, I am new to simulating transformers with LTspice, and I struggle getting the circuit to function as expected. The source is a three phase TN-S (wye) connected. Then I wanted to add a 1:1 ...
7k views

### Why would a three phase motor suddenly change it's rotating direction?

A pump is run by a three phase motor, after a voltage fluctuation suddenly the motor starts moving in the reverse direction. However, the motor is connected with a single magnetic conductor for ...
419 views

### Is it possible to connect a phase control relay to an inverter (VFD)?

Is it possible to check a motor ON/OFF state by connecting a phase control relay to the inverter and the motor 3 phase terminals? I have tested a phase monitoring relay to a main 3 phase supply from ...
94 views

### Symmetrical three-phase power flow problem, ā3

I have done quite a lot of research regarding the power flow problem for the steady state operation of an electric system. In many papers about the power flow problem the power flow equation are ...
85 views

### Can't get a small 3 phase generator to produce 1/10 of its rated output. I need a little help.

My concern I am writing about is with a small generator not producing current or being able to be loaded. First I'll describe the product. I bought a couple mini brushless 3-phase generators (motors). ...
459 views

### 3 phase BLDC sinusoidal drive using PWM controller and/or DSP?

My background is mechanical engineering (robotics). I apologize in advance. I have a sensitive torque ripple (Vibrations) application and would like to use sinusoidal drive to run a 3 phase BLDC ...
178 views

### 3-Phase Theory vs Practical example confusion

In theoretical examples, 3-phase circuits are shown as either Wye or Delta type. Wye obviously containing a neutral line. Recently I watched a Youtube video where the uploader re-purposed an old ...
239 views

### 3 phase generator residual voltage

A 3 phase wye-connected, 115 V, 400 Hz generator is used to power a test stand in which a motor controls a wiper arm that operates a three phase Variac to control the voltage across each of the phases....
5k views

### Why don't three-phase transformers use toroidal cores?

When looking at different transformer core designs, three phased, I never see any core designed as a circle or torus. Why is that so? Will it not work as well as the common B-shaped core?
928 views

### AC RMS current measurements with oscilloscope

I am going to measure the AC current(three phases), with a current probe, of a large machine, with an oscilloscope. The scope I am using has the following two options: RMS: RMS (Root Mean Square) ...
610 views

### Can I rewire a 240 V 3 phase steamer to a 240 V 1-2 phase?

I have this steamer unit that came in as 240 V, 3 phase that I am trying to adapt to a 1 (2) phase household. The unit needs 60 A and generate 9 kW. As per the manufacturer, and the below diagrams, I ...
1k views

### How do remaining two phases act as return path in three phase system

Since they are out of phase one against the other then there is a potential difference between them and the one that is on the higher potential is enclosed in the lower one. This is my assumption, ...
42 views

### Transformer impedence-question about problems

I'm given this transmission line problem in which I have a 3-phase transformer and I'm also given its impedence. I usually solve these problems using only one phase. So what should the impedence value ...
6k views

### Star delta phase difference

All I read online is that in a Y-Ī connection of a 3-phase transformer the voltage(phase and line if I'm correct) on the secondary side leads the primary one by 30 degrees phase. Does that happen ...
197 views

### Find transformer leakage reactance

For the short circuit test of a 3 phase transformer (star-star connected) I am given ( or have already calculated from previous questions) $$I=9720 A\\cosĻ=\sqrt 2/2\\P=300kW\\R=0.001 (phase)$$I am ...
2k views

### Star Delta Motor Starter, at higher ampere in Delta Configuration

Here is a dilemma. The electrician in my village isn't so much internet savvy as I guess(and I am not electrical expert) so I am asking this question here on his behalf. It's just similar to another ...
233 views

### Transmission line problem

I will first write the problem followed by the equations I'm given and then explain what troubles me. A 3-phase transmission line of 50 Hz and nominal voltage 400kV has the following per phase ...
596 views

### When are positive-sequence and negative-sequence equivalent impedance the same?

One of the topics we covered in an introduction to power systems class was using zero/positive/negative sequence networks to analyze faults in networks. For many problems, this requires setting up ...
67 views

### Different phases on different components

Say I have a typical wiring in my room where in I have two computers (A and B). A is a ...
109 views

### Converting Single Phase Mains into 3 Phases (No VFD) [closed]

I have a goal to build a circuit from scratch to simulate a 3 phase motor. I do not have any specific requirements, rather, I want to make sure that I understand what is wrong with my approach and ...
502 views

### Find impedence given per unit value-transformer

I really can't wrap my head around this. Three single phase transformers are connected to create a 3 phase transformer. They all have the same nominal values : voltage conversion : 1.2kV/120 V (...
1k views

### Transformer exercise problem

The transformer of the picture is connected to a transmission line of 230kV. As you can see the transformer is delta-star connected. Its turns ratio is a=1:10. I had a go at the solution but when ...
318 views

### Difference between a 3 phase VFD inverter and UPS inverter

this might seem like an odd question, but i consider myself still a newbie in Power electronics. This has been circling in my head for a few days. Intro : From a Hardware Standpoint i am assuming ...
5k views

### 32amp single phase or three phase [closed]

Sorry if there is a straight forward answer but my partner has converted a trailer into a drinks unit. She has a fridge a freezer and a coffee machine. Also about 5double sockets and lighting. The ...
2k views

### Why use three-phase power distribution? [closed]

My question is about phasing? Why phasing is needed in power line? Can't we just use one conductor instead of two or more conductors? I already searched for it, but couldn't get any relevant answer.
235 views

### Three Phase rectifier [closed]

I just bought a electric bike BLDC motor that i have to use as a DC generator, in order to charge a 12V battery. I have many questions, all related to this project but seeing it from quite different ...