Questions tagged [three-phase]

AC power with three legs run 120 degrees out of phase

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41 views

Which capacitor in series with resistor circuit to reduce remanence effects of transformer?

The "Comparative Analysis of Mitigation Techniques for Inrush Current of Transformer" mentions "Pre-insertions resistor with capacitor method" as an inrush mitigation technique: When circuit ...
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1answer
62 views

3 Phase “Black Box” Load

I'm doing a few basic load calculations on a 3 phase circuit at work and I stumbled on a concept I'm not sure how to proceed. Let's say you have a 3 phase load and it is basically a black box. For ...
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1answer
366 views

Confusion with applying KCL to three phase delta connection

Below is a 3-phase delta connected for balanced loads Z: Since phase to phase voltages(voltage across loads) have 120 degrees phase differences and since the loads have the same impedance we can ...
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0answers
500 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 (...
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1answer
2k views

Snubber circuit for 3 phase inverter designed for BLDC motor

I'm designing a motor controller for 3-phase BLDC motor. I'm using following components, Gate driver - IR2184 MOSFET - IRF540N The complete circuitry and output waveforms are available here. I have ...
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336 views

What will be the effect of putting a single phase load on an open delta transformer secondary?

Suppose I have an open delta transformer, 240 line to line secondary. I have a single phase constant power load I want to apply. I could apply it across either of the 'closed' phases and load that one ...
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25 views

3 phase power systems

why does a phase ground fault in an impedance grounded 3 phase system lead to variation of voltage in healthy phases but this variation doesn’t happen in solidly grounded systems? I was thinking about ...
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37 views

Why does a rotating magnetic field's frequency decrease, if we increase number of poles (induction motor)?

I absolutely don't understand it and drives me crazy. I've found several sources, in which there are shown images and animations about how two or three phase electric current generate rotating ...
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35 views

Rotating magnetic field discrepancy

This may be a noob question Lets consider a balanced 3 phase supply namely \begin{align} R&= V \sin(x)\\ Y&= V \sin(x-120)\\ B&= V \sin(x+120) \end{align} At a neutral point we would ...
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1answer
67 views

Problem understandin per unit system

I having trouble understanding PU system especially "briding" the gap from PU system -> to Actual system To illustrate this here is an example where I am given the one-line diagram for the three ...
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1answer
21 views

What is all properties of orthogonal axis (dq) axis?

We know about the transformation between abc three phase to dq0 axis which is orthogonal. BUT I am confused about What is the added value and all properties of orthogonality for dq0 axis that help in ...
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28 views

4Wire 120/208 High leg delta - 320v to ground, 420v to C phase?

I have a 120/208 High leg delta service 4 Wire. 208v/120v/120v The reason for the call is main breaker failed. I get there and the 1 bus bar is not being powered by the main but the other 2 are. ...
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2answers
110 views

Connecting DC Common Node (Ground) to Three Phase Neutral

I know I shouldn't. But I just wanted to ask due to a specific requirement. I also searched the forum but couldn't find any similar question. Please give me a link if there's any. I'm asked to modify ...
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0answers
51 views

How do I calculate the conduction angle in an uncontrolled three-phase full-wave bridge rectifier?

Basically I to calculate the conduction angle of the rectifier, with RLE load, I was taught to use some formulas and a plot but I not really how to calculate it from scratch, if you could explain it ...
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2answers
57 views

Induction from AC or RMF

I'm struggling to get my head around induction motors. Specifically, from what I can see the rotating magnetic field created by the 3 phases creates flux lines which sweep across the rotor bars which ...
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48 views

Pulse width modulation for three phase voltage source inverter

I have found a block diagram which discribes implementation of a modulator for the three phase voltage source inverter. I am not sure whether I fully understand this implementation of the modulator. I ...
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1answer
110 views

Calculating heat generated by resistance wire on 3 phase current

I am designing a heating element consisting of resistance wires coiled around a tube to heat water flowing in the tube. All three heating elements (loads) will have the same resistance and will be ...
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50 views

Calculations for 3-phase circuit in multisim

I have homework exercise which is looks like, and I'm trying recreate situation in multisim. Is my approach is good - are values of elements are proper? After calculations I will end with some exact ...
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2answers
45 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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0answers
116 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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0answers
34 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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0answers
88 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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89 views

How do I bring back to life a very un-excited 3phase 10kVa alternator

We are restoring a water mill and have recently got our 2 wheels turning once more. One of them is connected to an existing 3phase 10KVa alternator which although a little old seems to be in good ...
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70 views

Is there a cost savings associated with 3 phase power at the same device power requirement (kW)?

I am a Mechanical Engineer looking into purchasing an annealing furnace and have seen that some operate on single phase power while some operate on 3 phase power. I've done some research and have seen ...
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1answer
828 views

How to design a 3-phase resistive load bank?

We are trying to design a 3-phase resitive load bank to test some step up transformers. We are receiving 3-phase 208v and stepping up to 3-phase 600V with 3-step up transformers wired in delta. Its a ...
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105 views

Can we assume 230VAC in 3 phase system between phase and neutral?

If all devices connected to a 400V 3 phase power system are balanced and have a perfect power factor, can we assume the voltage between each phase and neutral is 230V? Why: I want to measure real ...
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1answer
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 ...
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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 ...
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1answer
458 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 ...
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1answer
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 ...
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0answers
592 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 ...
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65 views

Describe this type of rotor from a three phase induction motor?

After CNC machining the rotor, to expose the outer surface of the silicon iron, this proves to be exactly the same as the inner surface was (the one facing the core).Just plain electric iron rings ...
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118 views

Without converting the secondary side to “Y”, how would one solve this question?

The question: "A three-phase 230 V, 27 kVA, 0.9 PF (lagging) load is supplied by three 10 kVA, 1330/230 V, 60 Hz transformers connected in Y-Δ by means of a common three-phase feeder whose impedance ...
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197 views

Effect of the neutral current to a system when a 3-phase facility is used as unbalanced

Normally 3 phase-systems are used for balanced loads like in 3-phase AC induction motors. I know that in a balanced star configuration the total current across the neutral is zero. But what if each ...
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494 views

Two-quadrant sinusoidal (3-phase) PWM generation

I have a true sinusoidal BLDC driver, PWM of which works in Bi-polar, Complementary mode. I have to make it Uni-polar independent or Bi-polar independent, so the operation to become two-quadrant ...
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0answers
702 views

3 Phase power logger with ADC and Raspberry Pi

I am building a 3 phase power logger with the ability to measure 3-phase AC and 2 DC inputs as well for a final year project. A typical application would be measuring a small inverter for a solar ...
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85 views

Measure 3-phase Power with Lecroy Waverunner

Please note that experience with a Lecroy Waverunner Oscilliscope is most likely required to answer this question. I'm attempting to measure the power draw of a brushless 3-phase motor with a Lecroy ...
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0answers
108 views

Purpose of resistors from phase to phase on 480V motor

I have inherited a project with a motor circuit that I cannot figure out the purpose of some resistors. It was initially designed for operation in Europe at 400V 50Hz. Since it is operating here in ...
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336 views

Wiring diagram and phase number of three phase transformer

Does anybody have an idea how to draw vector diagram of primary and secondary of a three phase transformer? For instance, if I need to draw vector diagram for Yzn5 diagram and then also draw the ...
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175 views

How to add a desirable phase shift in the input from 3-phase ac mains?

I want to build a 12 pulse rectifier circuit. I know delta-wye or wye-delta transformers can be used to add phase shifts equal to the multiples of 30, but I don't want to use transformers. Is there ...
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0answers
79 views

Rotation-switched active rectifier idea

Most of you will know how three-phase rectification works and how cool it is. My idea is: replacing the diodes in a three-phase full-wave diode bridge with MOSFETs, as in active rectification, and ...
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0answers
230 views

Missing phase 3-quadrant TRIAC-based solid state relay for 3-phase engine

First of all, I'm a simple mechatronics technician student first time posting here, so please don't mind if I say something that seems completely stupid, since I consider myself to be a total newbie ...
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0answers
134 views

Faulted phase detection

Currently I am studying about short circuit detection on long lines and I can't solve one task: I have line between two substations, and there is short circuit some where on this line. I know current ...
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1answer
73 views

VFD as general use inverter

I'd like to have 3ph 208 in my house for general use (not a motor). If I run the output of a single phase to 3 phase VFD through inductors or a 1:1 transformer will it smooth the SPWM .output into an ...
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1answer
1k views

What happens if we run 415V 3 phase motor running on full load on to a 240V 3 phase supply?

I have a 415V 3 phase motor, but during emergency situation a 110V DC to 220VAC 3 Phase inverter comes into place. What will be the effects on the motor
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16 views

Is it safe to bundle together 380V cable + 24V signal cable + network cable?

I have the following cables between two machines: 380V 3-phase power cable 24V signal cable EtherCAT cable I would like to create an interface using a modular connector such as the one in the ...
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32 views

Shoot through problem in 3-phase BLDC controller circuit

I have designed a 3-phase controller for a BLDC motor. I am checking one side of the bridge with a Pico-scope for shoot through. The wave-forms below are indicating that i am getting shoot through, ...
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1answer
31 views

DC unregulated power supply

I want to make a 70 VDC power supply, output unregulated with +/- 10V variation allowed. I also want 50 A current from it. My input can be 3-phase 380 V mains supply. I cannot think of a 3-phase ...
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1answer
45 views

Single and 3-Phase Load Calculations

I have a probably obvious question about powering single phase loads from two legs of a 3 phase supply and how this impacts current draw calculations. This is something that is commonly done in my job ...
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1answer
37 views

Understanding voltage sampling rate of induction motors

Why it is required to have a sampling rate of at least 4kHz when sampling the voltage waveform of a three phase induction motor? I find most research papers use 4kHz but they don't state why. I want ...