Questions tagged [three-phase]
AC power with three legs run 120 degrees out of phase
499
questions
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26 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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0answers
26 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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0answers
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
32 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
93 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
71 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 ...
0
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1answer
41 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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0answers
19 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
47 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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0answers
19 views
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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0answers
20 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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0answers
46 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
27 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
30 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
170 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. ...
2
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1answer
92 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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3answers
102 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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0answers
54 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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0answers
49 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
57 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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0answers
32 views
How do I calculate deformant and real power of this circuit?
I have this circuit, the load is RL:
I need to calculate the apparent, real, reactive and deformant power assuming L is very large. Since L is very large that means Q= 0 var and Pload=~Uav*Iav and S=...
1
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2answers
115 views
Which one of these is the phase 1? [closed]
Which one of these is the phase 1? And why isn't there a neutral wire at all? The cable is Chinese. The device it powers is a 3-phase motor that powers hydraulics. I am sorry for asking this question ...
0
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1answer
51 views
Effect of Reversed Phase Polarity on Active & Reactive Power of 3-Phase System?
I am trying to investigate the Power/Energy of 3-Phase System under Different Faults.
I have a Three Phase Source and Load, Load is balanced i.e same phase angle and current (Phase-Neutral V = 230 ...
0
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1answer
40 views
How to calculate V/f value for an Induction motor?
I want to implement constant V/f in variable speed Inverter of a 3-phase Induction motor, 1500 rpm, 4-poles. I also know the equation:
V/f = 4.44 × N x Phi
Phi is maximum value of flux, f is ...
0
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1answer
53 views
Why would a motor manufacturer offer multiple coil winding types?
I'm currently looking through a part catalog from a motor manufacturer and notice that you can purchase this motor with different motor winding types. Specifically, you can order the motor coil wound ...
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3answers
83 views
Can a single phase SMPS be converted to run from three phase?
If you have a switch-mode power supply that runs off 240 VAC single phase, is it possible to convert it so that it runs off 3P+N (415V phase-to-phase) by only changing the bridge rectifier?
I have ...
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0answers
31 views
Power in balanced three phase systems
I was solving the following exercise
And got the a) and the c) correct:
\$\ Iline = 14.6 - 5.95j (A) \$
\$\ power factor = 0.926 \$
I turned the delta connection into a wye connection and got:
\$...
0
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0answers
19 views
How to change V and F in constant V/F control of an ACIM?
If I generate 3-Phase PWM outputs to drive a 3-phase ACIM and use constant V/F method for speed control then how will I change V and F of the generated PWM outputs?
I will generate PWM's using LUT ...
1
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1answer
50 views
Converting single-phase to three-phase for City & Guilds 2391 practical
For my City and Guilds 2391 course, I will be testing a three-phase distribution board with a motor and single-phase sub-main.
I am finding it hard to memorize the test procedures. So for me it's ...
1
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1answer
65 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 ...
0
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1answer
30 views
Loading one line from Three Phase Power Delta Configuration
I have been trying to determine whether or not I can run one line from 3-phase power into a power conditioner that requires single-phase input.
The current draw on this line would be around 10 A. ...
0
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1answer
66 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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1answer
82 views
What is the formula for calculating the no load current of a 3-phase motor? [closed]
I am looking for the formula, not a rule of thumb. Is there a way to calculate the no-load current?
2
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1answer
10k views
Why don't the currents clash in a 3 phase delta connection?
Consider 3 windings, a, b and c. L1 is connected to A, L2 to B and L3 to C. The 3 windings are then connected in delta.
If we could freeze frame the voltage waveform where L1 and L2 are positive ...
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1answer
90 views
Cable size for 3-Phase 800 Amp
On a 800 AMP heating unit that is fed from 480VAC, 3 phase power. Will each conductor pull 800A or 266A ?
2
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0answers
36 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 ...
0
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2answers
89 views
What is the power of a three phase circuit?
P = sqrt(3)*U * I * cos(f) is the real power for a symmetric load (U and I are RMS values of voltage and current of a single load), but what about generators?Do they have to have equal electromotive ...
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0answers
32 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 ...
0
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1answer
50 views
What AC mains phase information can be deduced from measuring at two distinct devices, connected via ethernet?
I a have a house with 3x20A grid connection. With the usual big loads like washing machines, kitchen. For each socket in the house (many...) I want to determine the phase a wall socket is connected to ...
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2answers
43 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 ...
0
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1answer
57 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 ...
0
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0answers
41 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 ...
0
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1answer
102 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 ...
0
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0answers
74 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 ...
1
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1answer
51 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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0answers
36 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 ...
0
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0answers
86 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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0answers
46 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 ...
5
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5answers
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?...
1
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1answer
47 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 ...
