Questions tagged [three-phase]

AC power with three legs run 120 degrees out of phase

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77 views

Three phase motor too high no-load current [on hold]

I got an old three phase motor (20+ years) which consumes more current than it should. The motor specs are: ...
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2answers
38 views

How to find phase sequence in 3 phase system using micro controller without zero cross over?

I have 3 ADCs which are connected to 3 phases respectively. I have to find the phase sequence when it comes in picture... I'm getting an ADC value for particular phase, but how can I find the sequence ...
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1answer
44 views

Trouble in understanding current flow in this three phase DC-AC inverter circuit

Shown in the figure is one of the six steps of a 3-phase voltage source inverter where switches 1,5,6 are closed. The tutorial that I learnt this concept from draws the following equivalent circuit of ...
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37 views

Phase voltage of a three-phase source with impedances knowing the line voltage

How can we determine the phase voltage of a balanced triangle three-phase source when impedances are present in that source and knowing the line voltage? When we only have voltage sources, the line ...
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1answer
82 views

Designing a 3-phase pure sine inverter. Where do I start? [closed]

I'm trying to design a 3-phase pure sine inverter which will be powered by a 128 cell battery bank (3.0v-4.2v/384v-537v). Since 384v is still above the 325v peak of a 250Vrms sine wave, I figured I ...
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73 views

Calculating power from voltage (V) and amp (I) values

First of all I would like to say that I am not familiar with electronics at all. So we had an exercise during the lecture and the exam is soon. The professor calculated P value of 230V and 16A very ...
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1answer
47 views

Three phase system represented as a vector

In multiple locations I've been seeing the following: "Any three phase system can be defined by the vector As: \$ A_s = \frac{2}{3}[Ax(t) + (c)Ay(t) + (c^2)Az(t)]\$ Where \$ c=e^{j\frac{2\pi}{3}} \$...
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32 views

calculate phase voltages based on a PWM signal

Is there a method by which I can calculate phase voltages based on a PWM signal? I have as input PWM feedback signals and the DCLink voltage and as output there should be calculated voltages for each ...
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75 views

3-phase rectification using individual step down transformers for each phase

I'm looking make a simple low-voltage DC power supply from a 3-phase supply. Looking into 3-phase rectifiers I came across the below articles https://www.gprectifier.com/news/rectifier-11261763.html ...
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42 views

Is there such a different phase control relay?

PROBLEM The standard phase control relay is output from any phase. However, there will be no output when that phase is gone. PROPOSAL When any phase is gone, the switch of the phase distribution ...
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1k views

Three phase systems - are there any single phase devices that are connected between two phases instead of between one phase and neutral?

In star system, single phase consumers are connected between a line and neutral but are there any single phase devices connected between two phases (would that even be considered a single phase device?...
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1answer
41 views

Generic 3 phase relay switch

I have a water fill level sensor which is capable to power a 3A single phase 230V motor. However, I have a three phase water pump. Is there a generic "switch" / relay which "operates" on single phase ...
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1answer
41 views

Protection on the AC side vs DC side

The circuit below shows a three phase rectifier with 3 filter inductors at the input side, and a capacitor, a MOV, and fuse at the output side. I wonder what the differences are in protecting the AC ...
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1answer
73 views

How to determine time needed to stay in a voltage vector state in Space Vector PWM for 3 phase inverter?

I need some clarifications on how and when to switch between voltage vector states (for the sake of discussion lets take V1 and V2 in the image below). Below is the image of 6 possible voltage vector ...
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1answer
41 views

Three phase systems - when is potential of a star node equal to zero?

I had to find total impedance of the following three phase circuit with symmetric line voltages: I've been told that nodes 1 and 2 can be connected because their potentials are equal (zero).After ...
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2answers
768 views

Why is the air gap between the stator and rotor on a motor kept as small as it is?

Between the stator windings and rotor is a small air gap. What would happen if this gap were larger than it is? Surely the magnetic field set up by energizing the stator windings would still cut the ...
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1answer
41 views

Does using only 2 phases (400V) in a 3 phase transformer affect anything?

I just witnessed a 3 phase control transformer in the mcc that steps down 400V to 230V connected only with 2 phases on the 3 400V terminals, and on the other side (secondary) are your live and neutral ...
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1answer
117 views

What is the purpose of these diodes?

What is the purpose of these didoes? I couldn't find it because I don't know it's name. Thank you. simulate this circuit – Schematic created using CircuitLab
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1answer
43 views

Correlation b/w output voltage frequency and angle theta for Conventional Space Vector PWM 3-Phase inverter drive

Im writing code for SP-PWM for a 3 phase voltage source inverter but since im a bit naive to the topic I need some clarifications regarding some questions I have. Lets cut to the point. For 3-phase ...
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0answers
109 views

Why are all my motors and transformers failing at this specific location?

At my job there is a vacuum oven. There is a 50 hp, enclosed cooling fan. that circulates N2 gas upon quench, the design of the unit runs 480 volts through a reduction transformer to 230 volts. This ...
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1answer
65 views

TVS diodes in series

In the picture below, there are three TVS diodes in series (D13, D14, D15). They are placed from drain to -13V reference, which is the reference for the rectifier. The diodes are 1.5KE300A, they have ...
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3answers
226 views

Understanding this power supply design

I'm doing some kind of reverse engineering to this very old power supply design. I'm having hard time trying to understand it all. I'm asking for some hints that help me read this schematic. From this ...
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30 views

How to choose high frequency inductors for high voltage line filtering?

I saw these inductors 680 uH (RL-1294-680) in each power line like shown below. The line to line voltage is 480 VAC. The inductor used has a saturation current of 280 mA. So I suppose I shouldn't ...
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1answer
37 views

RMS value of a line to neutral voltage on a three phase inverter

Basically, I feel like this is an incredibly simple thing, but my brain is stuck on it for hours now, and I can't find the answer anywhere. How do I find the RMS value of the signal shown, assuming ...
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3answers
108 views

12VDC to 3 Phase 400V

In order top prevent my seldom used deep well pump (3 Phase, 400V) I plan to daily spin it up for a few seconds. Where the pump is located, the is no power supply (I operate the pump using a ...
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1answer
70 views

How can I find the slip speed of a slip ring induction motor without knowing the rotor speed (rated RPM)

The Rotor of a 4 pole, 50hz slip ring induction motor has a resistance of 5ohm per phase and inductance of 150mH per phase. Calculate the slip speed at which max torque occurs. I have used Ns = 120f/...
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35 views

How to estimate the power consumption of a motor when running at low load

I am trying to calculate the electrical power cost-saving of reducing the amount of time a machine runs idle (when the motor is running unloaded). From the meter data, the amps when idling is about ...
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1answer
391 views

An overseas company is making a machine for me and they need to know whether I want 1,2 or 3 phase and what voltage

I'm in Quebec and the company making the machine is in China. The machine is an industrial sized T-Shirt sublimation machine that does two sided printing. So there's a large heated plate that is ...
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1answer
39 views

Transformer Sizing with Mixed Loads (Three-Phase & Single-Phase)

I am trying to size/validate the rating on the medium voltage main transformer for an industrial plant. For some reason I can't find many resources that indicate how to properly do this when you have ...
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1answer
199 views

Identifying direction of rotation for a three phase motor, without applying three-phase power

Suppose I have a typical smallish (say, <3kW) three phase induction motor. Likely 400V star-connected, but methods that work with any motor would be preferred. I can ensure that the supply phase ...
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4answers
676 views

Does the neutral wire have any voltage?

In this article, the author talks about 3 phase and the magic of a missing neutral wire. And there's the following paragraph: In a 3-phase system the voltage between any two phases is 3 times ...
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102 views

AC water turbine

I am trying to use a water turbine from China to charge a lithium ion battery. The water turbine is rated to 10 watts. I figured that should be enough to charge the battery but I can only ever get ...
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3answers
115 views

Can a Variable Frequency Drive convert standard wall outlet (120V/15A/single phase) to ~220V 3 phase?

In my workshop I have a device that requires 220V 3 phase power, with a requirement of up to 1.5kVA. In North America, my wall outlet provides ~120V/15A single phases. (EDIT - my device can take +/- ...
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1answer
75 views

How to detect the phase sequence of a 3-phase ac (R-Y-B or R-B-Y) using Atmega32?

I am using an 8-bit AVR microcontroller in my project to detect the phase sequence of a 3-phase AC supply. Which method shall I use to do the work with the least number of components required along ...
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55 views

Problem with Line to Line Voltage Output in 3 Phase Inverter MOSFET Bridge Circuit

I have a problem in my 3 phase inverter circuit output. Below, i've attached an image of my circuit. As you can see, i have 3 outputs. There are R, S, and T. So, i've measured line to line voltage ...
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3answers
91 views

How to verify if all 3 AC phases are in order? [closed]

We have 220V main lines where we currently live and we have a 3-Phase connection. We have an Air conditioning unit that requires 3 phase AC input with the correct phase sequence. If the phase ...
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1answer
47 views

Does a 3-phase VFD work if one phase is reduced (e.g. with a dimmer)?

If you have a 3-phase VFD running a 3-phase motor, and you use a leading or trailing edge dimmer on one or two of the input phases, will the VFD continue to operate normally, pulling more current from ...
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43 views

Is a load bank always 3-phase or is a 4-phase possible?

I am designing a low voltage installation and the customer asked for a cell for a load bank. Now he drew this in 4-phase, but I did not encounter this before. Is this possible? I thought they were ...
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1answer
56 views

Phase Voltage Confusion

Here's a question that I was asked with the answer keys. From the problem I deduced the net load impedance for one of the elements in the delta configuration will turn out to be 172.767|_3.66194 Ohms....
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35 views

Loading an AC generator with DC Chopper + resistor

We're in kind of a bind at work and looking for easiest / cheapest way to load an AC generator (Synchronous permanent magnet machine). We have access to a big 300A Mosfet module along with it's ...
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1answer
45 views

PWM phase voltage and current measurement for power consumption calculation for a BLDC MOTOR

I have been trying to log both voltage and current from the battery of an electric two wheeler for finding out efficiency at inverter, battery level.
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3answers
152 views

Figuring out neutral and earth in a three phase connector?

I’m trying to check whether the earth and neutral is connected correctly in a 5 pin connector which has 3 pins for lines, one for neutral and one for the PE earth. 3L-N-PE type connector. For some ...
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1answer
51 views

How to create EMI/EMC noise for testing product behavior in noise environment?

We have product which works on three phase AC supply. We were facing issue on I2C interface of external RTC due to noise from external environment. After some inspection, we realized that because of ...
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2answers
467 views

How is Line and Phase Voltage the same for a Delta connected system?

I am having a little bit of confusion for some reason understanding how the phase and line voltage can be the same for a delta connected system, i understand why the current is different for the phase ...
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1answer
65 views

How does torque control work in three phase motors?

For a project I am working with a three-phase AC brushless motor, connected to a motor driver. The driver allows digital control over the motor in position, velocity or torque modes. Below are a few ...
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41 views

How to calculate R for an AC load on a 3-ph system

I'm trying to calculate the resistors in an AC dummy load for a 3-ph system. A simplified schematic can be found below. The idea is to switch (with regular AC 1-ph contactors) some resistors on each ...
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1answer
62 views

Per Unit System: what details am I missing

Ok, so I had a problem about a three-phase system with the following data $$V=220kV$$ $$S=150MVA$$ $$\cos \phi=0.85$$ where V is the phase-phase voltage, S is apparent power, and \$\phi \$ is ...
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58 views

Circuit for Neutral point of 3-Phase mains

I wonder if the 'Neutral Point' as mentioned in the attached image is correctly labeled or not? Is there any mistake in this 3-phase circuit design? Edit 1: Also it looks like the 'Neutral point' is ...
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65 views

24V, 3 Phase BDCM Controller Schematic

This may seem like a dumb question, but does anyone have a schematic for a BDCM controller. All I seem to be able to find are partial schematics or schematics that include a micro controller. My ...
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1answer
107 views

DIY 3-phase fast linear actuator

I have a need for a FAST linear actuator of which I may control position and speed reliably. I have already been looking into pnuematics, however it does not seem that this will fit my needs (I am ...