Questions tagged [three-phase]

AC power with three legs run 120 degrees out of phase

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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
112 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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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 this ...
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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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59 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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314 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
36 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
111 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
59 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
199 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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245 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
34 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
83 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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40 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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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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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
50 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
74 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
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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25 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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53 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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40 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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50 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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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
131 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
172 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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899 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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80 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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53 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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67 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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42 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=...
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119 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 ...
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1answer
312 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 ...
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1answer
98 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 ...
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1answer
59 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
192 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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33 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: \$...
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22 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 ...
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1answer
52 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 ...
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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
32 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. ...
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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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477 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?
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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
193 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 ?
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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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