Questions tagged [three-phase]

AC power with three legs run 120 degrees out of phase

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57 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
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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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33 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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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
95 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
65 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
51 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
65 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
23 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
67 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
54 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
86 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
91 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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44 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
113 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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24 views

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
29 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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2answers
64 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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1answer
56 views

Smoothing out current spikes so three-phase machine doesn't exceed site's electrical supply

We are looking at installing a machine at one of our manufacturing sites that draws around 120A at 415V three-phase (we are in the UK) but the maximum current we can draw at our site is 100A before ...
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1answer
66 views

How to find phase shift(angle) between two signals in simulink?

So I'm doing a delta wye transformer in simulink and phase shift between these two signals should be 30 degrees, but how to show that, or calculate it? And how to find angle of each signal?
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40 views

How to show that voltages on diagram are 120° apart?

So i'm doing a matlab simulation of delta wye transformer and would need to show the phase shift between voltages. Here is a picture of input voltages so how would I show on this graph mathematically ...
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1answer
25 views

How to find the apparent power absorbed by a three phases load?

Given a symmetric and balanced three-phases circuit, I would like to calculate the apparent power absorbed a three-phases delta load. I’m given the rms value of the line voltage applied to the load, ...
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1answer
80 views

Is it a good practice to put multiple capacitors in series to obtain higher voltage rating in medium voltage system?

I am building a DC link for an IGBT based inverter. The input is provided from a 400V 3 phase AC source. I couldn't find capacitor rated greater than 450V in my nearest stores. I'm thinking of ...
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36 views

can I have many / multiple loads on a 3 phase circuit?

Sparky question: Can I have more than one load on a TP circuit? Specifically a radial circuit with 2 x TP induction motor roller shutter doors. If not, why not? Thanks in advance. :D
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49 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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27 views

Why is line-ground voltage higher than line-line at the output of a variable frequency drive

I am using a Fluke 87V, reading AC voltage with the low pass filter activated. I have also used a stray voltage eliminator and the readings are the same. Between each of the phases I read about 38VAC....
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24 views

Three Phase Rectification using by Bi-directional N-MOS Switch

I have been trying to design three phase rectifier using by bi-directional N-Channel Mosfet . However, Non-isolated gate driver is not able to open and close U4, U8 and U12 on image. What kind of gate ...
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2answers
35 views

Motors in symmetrical fault analysis

In three phase symmetrical fault motors(Induction and Synchronous) become generators(I guess because of the inertia). When do I take in consideration of the motors? Do I even need take them in ...
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1answer
99 views

What determines generator frequency besides engine RPM? [closed]

I have a 230 V 3-phase generator, which runs at 180 Hz. Can I change the frequency to 60 Hz?
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1answer
73 views

I have a specification sheet that says the load is 15 kW, 480 V, 3 phase. Is that 15 kW on each leg or 15 kW total?

Basically as the title asks. I am having trouble wrapping my mind around this. If its 15 kW on each leg my thought is that you are paying for 45 kW of power but I feel like it would be more common ...
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2answers
55 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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22 views

Does zero sequence current flow in line to line faults?

Assuming that there is a prefault load on a line,does zero sequence current flow during phase to phase faults ?
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1answer
50 views

Circuit to run a 3 phase magnet generator as motor?

I am trying to convert a wind generator to a brushless motor. As you can see at the image, it has 16 magnets and 12 coils. The coils are connected as 3 phase, star connection, so I have 3 output ...
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Find the load capacitance of a phase in a three phase circuit

I'm new in electronics circuits, and I came across a problem that asks to find the load capacitance of a phase such that \$cos(\phi)=1\$ on a three phase circuit where the load on the Y source is ...
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33 views

Transmission Line Impedance 3 phase

I have the following question that I can't seem to figure out. The question ask to solve for the impedance of a 3ph transmission line. I've found the De (distance relative distance) and XL using the ...
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47 views

Wye to delta 3 phase

Can someone please explain to me the following. For the last part, why did they use the Van to find Vab( secondary line voltage of the delta). I did it and my magnitude matches the solution but the ...
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0answers
37 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
58 views

What happens to the Real and Reactive power when I increase the excitation current in a 3-Phase Synchronous Generator?

Basically my doubt is, for the same load, why does the Real power remain constant when I increase the excitation current?
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1answer
171 views

Help on (another) triphasic exercise

Second this week... But was it easy I wouldn't be here... A problem asked me to identify the diagrams from this picture: The following are the correct answers, acording to the test developers. a. ...
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1answer
93 views

Help on a triphasic test exercise

On the above picture, VAB is 380 V, balanced loads. The right answer says power on Wattmeter A is 0 and power on wattmeter C is 7240 W. This question came from a previous admission test from a power ...
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312 views

Why is the three-phase voltage 440V, if single-phase alone is 230V?

Why it is not 230V ×3, why only 440V?
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61 views

Relation between phase angle and current direction

In a triphasic system (any), is there a way to tell if the current is entering or leaving a phase/line/load just by the angle of the phasor of the source ? In the following picture we can see the ...
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52 views

Stepper motor, why so many wires (10)?

I recently bought a stepper motor secondhand and out of curiosity opened up the back cover to see how the wires were connected, currently it looks like 3 phases are connected (4 wires, 3 phase wires, ...
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2answers
64 views

Relating input torque on BLDC motor shaft with output current

I am trying to build a drone generator with a gasoline engine and a 14-pole,170KV, 2KW BLDC skateboard motor (this one). Before designing the system and running it, I wanted to clear out a fundamental ...

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