Questions tagged [three-phase]

AC power with three legs run 120 degrees out of phase

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20 views

Wall Voltage in 3Phase

I have a relatively simple question on the grid voltage. When we say the voltage from the wall is 220 Vrms is that the line-line voltage or is that the phase voltage. ie are the two output lines from ...
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1answer
76 views

Simple 300-400VDC/100A power supply for EV charging from 400V 3-phase/32A

I would like to purchase or build a simple AC-DC power supply, with 400V/32A 3-phase input, and DC output adjustable (by a microcontroller which I would add) between 300-400VDC and upto 100A (not ...
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32 views

3-phase bridge inverter 120° conduction mode

A 3-phase bridge inverter is feeding a balanced star connected resistive load of 20Ω per phase. The gating scheme is 120°-conduction mode. All the switching devices are ideal. Derive the expression ...
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2answers
27 views

3-Pole Circuit Breaker with GPIO

I'm starting a small project involving 3-pole circuit breakers and 3-ph motors. There's this custom built machine with multiple 3-ph motors, each connected to circuit breakers. The purpose of the ...
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1answer
21 views

How to find the 120 degree phase angle in a single layered lap winding of a synchronous machine?

Ok, so I have a 4 pole synchronous machine with 24 slots meaning each slot has a phase difference of 30 degree with respect to each other. 1)That means pole pitch is 180 degree for a full pitched ...
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2answers
58 views

3 phase heating elements

Is there a simple way of calculating the power (kW) of a 3 phase heating element? I have 3 elements mounted in a pack and inserted into a tube and there are 12 tubes, so 36 elements in total. They ...
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3answers
83 views

How to run a DC device through 3 phace 400V AC mains?

So I need to put a wifi antenna on farmland, the issue is that the antenna needs 12V DC powered over Ethernet and the only power source nearby is a 3phase 400V AC one... So is there something like a ...
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1answer
35 views

3-phase inductance calculation homework

This is a homework question where i am stuck. Please help me out in this: Three similar impedances are connected in star across 2000 V, 50 Hz three phase supply. Power absorbed is 300 kW. ...
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2answers
125 views

Three phase system questions

I have been trying to solve homework questions on three phase systems but I am got stuck in two questions while solving solving them. Three similar impedances are connected in star across 2000V, ...
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0answers
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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When should we use \$V_L=V\$ when we prove \$P^1_{LOSS}=2P^3_{LOSS}\$.?

The book said when the transmission power and wire resistance of both one phase and three phase are the same,the power loss for one phase system is equal to two times power loss for three phase ,that ...
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2answers
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The problem when i proved \$3S_Y=S_\Delta\$ by using \$S=I^2 Z\$ in three phase circuit

There is the proof about \$3S_Y=S_\Delta\$ in lots of books I have other way to prove the \$3S_Y=S_\Delta\$,however,there is a problem in my proof,but i don't know where am i wrong As we can see the ...
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1answer
83 views

Voltage notch behavior

I am using software to simulate and learn more about 3-phase semi-conductor rectifiers (using SCR.) I also learn about the voltage notches due to the possible overlap between the SCR commutation. If I ...
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1answer
33 views

In what condition,we can have \$P_{\Delta}=P_{Y}\$,not \$P_Y=\frac{1}{3}P_{\Delta} \$

The power consumption of three phase circuit, which is connected with \$ \Delta\$ type, is \$3000W\$,now if we modified it with \$ Y\$ type,what is the power consumption of this circuit? The answer ...
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2answers
46 views

What are the standard PWM output signals that a microcontroller should generate for 3 phase motor control?

I am programming a FOC 3 phase motor controller on a Teensy4. The motor will be driven by 6 MOSFETs and a gate driver IC for the MOSFETs. I have looked though the data sheets for many different gate ...
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2answers
85 views

What does this symbol mean? And I have some basic problems which the book didn't mention

A power system book asked me this question, but honestly I don't understand the circuit of question and the solution which author provided. Question: There are 3 primary currents, \$I_R,I_S\$,and \...
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1answer
36 views

where am i wrong in my calculation?why is \$V_{bc}=220∠120°-120°=220∠0°\$,not \$V_{bc}=220∠-120°-(120°)=220∠-240°\$

A three-phase Y circuit with positive sequence (abc),now if \$V_{ab}=220∠120°\$,then what is\$V_{bc}\$,and \$V_{ca}\$ ? i thought Y circuit with positive sequence means \$V_{ao}=220∠0°, V_{bo}=220∠-...
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Windmill 3 Phase AC control PCB

I've created a PCB for my newly built 3D printed Windmill. Now I am not entirely sure about all the components and the way they function, so I'd like to have your opinion on the circuitry before I ...
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1answer
41 views

Three Phase Rectifier Question (student)

I am new to this forum. I am an Electrical Engineering student working on a project. I am using Matlab Simulink/Simscape to perform simulations. Currently, I am working on a three-phase rectifier. (...
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4answers
66 views

Can I use only one phase out of a triphasic cable?

Scenario There is a three-phase cable popping out of the wall exactly where I need to put a light bulb. Is it ok if I plug only two wires to the triphasic cable, (i.e. neutral and live 1) to achieve ...
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0answers
33 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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2answers
76 views

Step down 3 phase 2kV AC to 3-12V at modest current (5-20mA max)

I'm looking for a way to step down 3 phase, 2kV AC power to 3-12V DC. I do not have a neutral, just the 3 phases and ground. This will be entirely isolated, nobody will be anywhere near this thing. ...
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back to back SCR firing circuit

I am trying to design a 3-phase soft start circuit.Are these two circuits different? My PCB design and RC snubber between anode & cathode is based on the second one.I want to make sure my circuit ...
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31 views

Control 3 phase load with microcontroller

I am designing a circuit to control a 3 phase resistive load (400V & 30A). The idea is to control the circuit with a microcontroller io. Since it will switch very often (1 Hz aprox), i decided ...
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2answers
44 views

Will this 3-phase 208Y/120 setup work [closed]

OKAY...electrician I had out recommended the following setup to supply 3-phase wye 208/120v off of 240V single-phase. My device is pulling 30 amps, and my entire load is about 15KVA. It's impossible ...
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2answers
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Polyphase multivibrator (real vs SPICE simulation)

i have a following schematic for three-phase multivibrator: SPICE simulation shows that it should work (11 volts peaks on collector nodes): However, when i make this circuit on breadboard it does ...
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2answers
64 views

Converting single-phase 120 V or 240 V into three-phase 4-wire 120/208 V

I am needing to convert either 240 V or 120 V single-phase into 120/208 V three-phase 4-wire. The load needed is 30 A. My panel can supply up to 100 amps, so the amperage isn't an issue. I've looked ...
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1answer
62 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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1answer
39 views

The effects on torque/slip when changing speed?

I know that the number of poles altering frequency and voltage changes the speed but I don't know how either alters the torque or slip.
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terminal resistance of delta-wound BLDC motor

When the producers of BLDCs state terminal resistance and terminal inductance of a delta-wound motor, do they mean the R-L of the parallel between 1 triangle-side-coil and the series of the remaining ...
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1answer
28 views

Generator Output at different frequencies

If a three phase generator is stated as 200kVA, 440V, 60Hz therefore a current output of 262A. If said generator is changed to deliver 50Hz power at 440V, would that reduce the power available? so the ...
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5answers
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Why the triangle reference wave is used in PWM for sine modulation?

I'm implementing PWM for a three-phase inverter. The documentation on the subject, especially the technical implementations, is very good but as far as I am able to understand none of the one I read ...
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1answer
100 views

“Black box” transformer: Y-Y, Y-Δ, or Δ-Δ connected?

As a preface, this is purely hypothetical. I know better than to use a transformer without knowing anything about it. I'm just trying to get an idea of whether this is possible, not whether it's a ...
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2answers
68 views

What does 6kV , 5MW 90% efficiency at full load with 0.9 Power Factor lagging represent for a motor?

I am confused with I see such a statement like the following statetment: Motor with 6kV , 5MW 90% efficiency at full load with 0.9 Power Factor lagging. Could anyone explain it in simple words ?
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What is this eqation represent in Voltage phases?

I have three pahse load star connected, by per unit $$ |Vab| = 0.9 \\|Vbc| =1.16 \\ |Vca|=1.0$$ the phase angle is chosen $$ Vab = - 90 $$ then the next equation is used to find the different ...
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1answer
53 views

Can we prove the difference of phase between the voltage of three alternating current is 120 degree with “math formula”?

In the three-phase electric power,we will assume the difference of phase between the voltage of three alternating current is 120 degree I want to ask why do we assume the 120 degree is the best ...
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1answer
28 views

Wiring 3P+N Device to 3P+N+E Connection

I have a 415V compressor with a 3-phase Commando plug in the configuration 3P+E, however my wall socket is 3P+N+E. Is it possible to change the plug on the compressor to a 3P+N+E without connecting ...
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1answer
131 views

3 phase transformer problem

We were given the following problem. We spent a night but could not even get close to solve it. It would be great if you could help us solve it. Three identical 10 kVA, 19920/220 transformers are ...
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2answers
29 views

Calculating Phase wise Energy in Three Phase System

In three phase three wire system, is it necessary to calculate phase wise energy? As per my knowledge, in three phase three wire system we are concerned about only total power/energy. But does it ...
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3answers
81 views

What is limiting my BLDC Motor power Output?

I am using a BLDC 3 phase hub motor and recently installed a motor controller rated for 3000watt (I originally had a 1200Watt controller installed). The motor is rated for 500w nominal 800w peak but ...
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2answers
67 views

How does “delta”-like three phase power source avoid short circuit? [duplicate]

A delta-like 3-phase power source is as below: simulate this circuit – Schematic created using CircuitLab This diagram is equivalent to "Fundamental of Electric Circuits, 5 Edition" Figure 12....
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63 views

3-phase inverter - component selection / calculation help

Yes, this is a component selection / calculation topic, it can be considered an "ask". Considering my current schematic and the following parameters: supply = 100~240 VAC (nominal 220VAC and 127VAC ...
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2answers
103 views

Role of the neutral conductor in three phase systems

In a symmetrical and balanced three phase system no current flows on the neutral conductor. Obviously the real electric power distribution systems are not perfectly balanced, so there is a current on ...
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1answer
94 views

misunderstanding of Voltage output of a 3-phase rectifier

I simulated a 3 phase rectifier : I obtained V1 and V2 as plotted below : I dont understand that waveform as i'm supposed to obtain a DC voltage. Can someone explain me how it comes that i got ...
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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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56 views

Single phase neutral current & three-phase neutral current with respect to kirchhoff's law

In the below schematic, would be the sum of all current in the single phase neutral wires equal to the current in neutral wire going to the 3 phase main disconnect? In theory, we know that if the 3 ...
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2answers
226 views

Calculating total voltage/current for 3-phase?

Consider I have a 3-phase generator with the following measurements: Phase 1 (A): 22.8828A Phase 2 (A): 22.9922A Phase 3 (A): 22.9219A Phase 1 (V): 239.7656V Phase 2 (V): 241.8594V Phase 3 (V): 245....
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Applying DC bias on a high voltage rectified ripple 570VAC Peak down near to zero

I am working on a linear power supply with a 3phase input. I wondering if there was a possibility to shift the rectified(ripple) power signal shown below which spans between 560VAC to 505VAC ( 55VAC ...
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1answer
33 views

Delta wye transformer, voltages explanation?

So I'm doing a delta wye transformer simulation in simulink, and I need some clarification about transformer voltages. Here's a image from a youtube video We have phase voltages on primary that ...

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