Questions tagged [three-phase]

AC power with three legs run 120 degrees out of phase

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2answers
60 views

Three-phase circuit breaker trip current

If a three-phase circuit breaker is specified as, for example, a 32 A breaker, does this mean the breaker will trip when the current in a single phase exceeds 32 A, or when the total current of all ...
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39 views

How to calculate power supply output current from its three phase input current

In my lab I have three-phase electric power according to the following diagram: I'm using a three-phase power supply TRIO-PS-2G/3AC/24DC/40 which delivers 24V and max current 40A. Using a Current ...
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0answers
20 views

Mains power metering with both 3-phase balanced and single-phase loads

Let's say we have 3-phase, 4-wire mains power, that is, 3P+N (+PE but that's not really relevant for metering). If I have multiple (possibly unbalanced) loads between any phase and the neutral (=...
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55 views

UPS phase rotation issue

I have a 208 V 3~ 10 kW UPS backing up an environmental chamber. When energized the UPS faulted a reverse rotation alarm. I flipped the disconnect and changed two legs then re-energized only to get ...
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1answer
63 views

Electrical three-phase circuits [closed]

How can the luminosity of bulbs connected to a three-phase circuit be altered? Suppose there are three single-phase bulbs loads and they can only be connected to a three-phase supply, how can the ...
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1answer
65 views

Phase angle difference between the induced EMF in the rotor and the rotating magnetic field in three phase induction motor

I have been studying the three phase induction motor and in the process I could not exactly understand the EMF generation in the rotor. From figure(2) below, it is understood that the maximum EMF is ...
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1answer
55 views

Does a certain cable arrangement that reduces the generated magnetic field improve shielding properties as well?

If I arrange a three phase cable via phase-split into an arrangement that reduces the generated magentic field, does this affect shielding properties as well? To reduce the generated magnetic field of ...
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1answer
28 views

Why use vector sum for calculating neutral current?

In a three phase system, we use a vector sum to calculate resulting neutral current. I don't understand why we use vector sum. The resulting neutral current is actually the sum of instantaneous values ...
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0answers
57 views

How to test if a domestic 3 phase power company meter is reading wrong?

BACKGROUND: Domestic 3 phase 220VAC supply in Thailand. Power company meter is 4 wire GE 3 phase 15A/45A. Massive power bills when mains breakers were turned off (back in home country for 9 months ...
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39 views

Three- phase circuit

W1 's reading=1000W, W2's reading =600W,the line voltage =220V,the connection is balanced,delta-connected, how to find the impedence?Do I have to find power factor and line current in order to find ...
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2answers
57 views

In 3-phase motor control, what are the physical meanings of the `d` and `q` axes?

The axes have interesting properties, such as the fact that in low saliency permanent magnet motors (outrunners are common examples of this) only the current in the q-axis creates torque. But the ...
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24 views

Converting Delta-Wye to Wye

To convert the delta part of this circuit to wye, is it correct to do (6-8i)/3 and then to combine the two wyes, as they are in parallel, do (6-8i)/3 // (4+3i). Then will this form one wye which is 2....
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42 views

Motor/Generator Set Using Car Alternator

So I've recently been learning that car alternators are just three phase synchronous motors with external DC field excitation. To access the three phases it may be necessary to take them apart, ...
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3answers
82 views

Confusion regarding three phase system

I'm confused regarding 3 phase systems. In some texts I have seen three independent and separate sources. In some YouTube videos I have also seen the same, especially in software simulation, but in ...
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2answers
53 views

3 phase electric motor torque output

I am a mechanical engineer and fairly new to real life usage of electric motors. I have a 2.2 kW 3 phase AC motor. At 1450 rpm, it can generate 14.49 Nm torque (I understand this is called nominal ...
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46 views

Sufficient electric safety protection with MOVs?

I am developing a PCB that will carry 32 A currents. In order to protect the rest of the circuit and the 3 phase load I have added some protective measures to suppress transient voltages and short ...
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0answers
56 views

Can I solve Y-Δ circuit by converting it to Y-Y? Or do I need to solve it using Y-Δ formula?

Above is the picture of how I approach the 3(ii) question. My question is,which way is the correct way of finding line/phase currents/voltages? Why is the line/phase current different for each method? ...
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2answers
35 views

Delta to star transform currents

When we transform a delta circuit to a star circuit it is easy to transform the voltages and the resistances. In the case of a delta circuit between current flows only between 2 nodes while in a ...
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1answer
52 views

3 Phase breaker - Current Limit

I have a simple question... If I have this 3 Phase breaker: That means its current limit is 20A right? My question is, is it limit for the whole breaker or limit for every phase separately?... What ...
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2answers
139 views

Sign of 3-phase instantaneous reactive power and phase sequence

For three-phase systems, in p-q theory instantaneous reactive power is $$ q = \frac{(v_a-v_b)i_c + (v_b-v_c)i_a + (v_c-v_a)i_b}{\sqrt{3}} $$ (see, e.g., [1] Eq. (5)) If we substitute in expressions ...
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Are three-phase bridgeless boost, three-phase totem pole and active 6 switch rectifiers different names of the same topology?

I keep coming across these topologies in several references and they look similar but the names are used interchangeably. I wish to know if these are same, and if not, what is the difference between ...
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3answers
132 views

Replacing a 3-phase speed-varying drum switch with a VFD?

I am working on a stock feeder / power feeder (used with woodworking equipment). It has an 8-position drum switch to control both fwd/reverse direction as well as vary the speed. The ON positions of ...
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1answer
55 views

Design considerations for 3-phase AC-DC converter 60 vs 400 Hz

If I want to convert 400 Hz, three-phase, 200 VL-L to 28 VDC, how would I go about doing that compared to a conventional 60 Hz equivalent. In other words, what design considerations need to be taken ...
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3answers
80 views

Combining two identical 3-phase AC sources

I have a micro hydro setup. The generator is a 3-phase AC motor scavenged from a Segway ES2 scooter rated 36 V, 300 W continuous, 700 W peak. It is being rectified to DC. I thought that would be ...
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1answer
44 views

How can I calculate annual energy demand (kWh) used by a three-phase data centre?

I have output parameters from a data centre which details three phases: ...
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4answers
88 views

LTspice error, "Matrix is singular" for 3 phase circuit

I have been searching about it online but all I can find is info about a transformer. Am I missing something? Here is the circuit: This is the circuit I am trying to make:
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1answer
179 views

Why an iron disk doesn't rotate at synchronous speed in a 3-phase AC motor?

When we introduce an iron star inside the stator of a 4-pole 3-phase AC motor and then generate the rotating magnetic field, the star being made of a ferromagnetic material is magnetized and starts to ...
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1answer
89 views

How to calculate voltage between AC phases with different angles? [closed]

I am trying to understand some fundamentals about AC three phase wave forms, in this case is related to how to get the voltages between phases in real environment that as we know they have different ...
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2answers
235 views

Decoding Marathon electric motor model number

I have a 5HP 3-phase electric motor with the following model number / code: WVK 184T TDR 7026 DG It would be nice to decode this fully, but mainly I'm interested in ...
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2answers
88 views

What is the difference between three phase current and direct current?

I am currently reading about three phase current and its advantages. One of these advantages is that the voltage of a balanced three phase system will be constant, \$ V_{AN}(j\omega) + V_{BN}(j\omega) ...
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2answers
91 views

Determining the RMS current of diode of a 3 phase rectifier bridge with a filter capacitor and a load

I would like to know if it possible to determine the RMS current through a diode of a 3 phase rectifier. Here is the simulation. I was looking if I could neglect the effet of the smoothing capacitor ...
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34 views

IEC 60664-1 clearance between phase and earth

With IEC 60664-1 you require clearance between phase and earth. But if you have a resistor voltage divider between phase and earth do you need the same clearance between the pads of the resistors? Or ...
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1answer
64 views

3 phase inverter circuit mosfet burn out

I've designed a three-phase inverter for a hobby project that I'm working on and have had the board assembled. I'm new to this sort of stuff so learning as I go. I've attached the schematic. Initially ...
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37 views

Three phase power supply for test purposes

I work in the electrical industry and deal with mainly three phase power. I'm trying to broaden my knowledge of scopes and power quality and the only time I really have to do this is at work and that ...
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1answer
52 views

Computing power of 3 phase system without knowing the load configuration

I am trying to find out the power consumption for a 3 phase balanced system below: I only have access to the L1, L2, L3 and N connection points at the main connection box and I only know that it is ...
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0answers
29 views

Need help figuring out 8 heater PID controller circuit

I am building heater controller system for 8 heaters using PIDs and contactors. Heaters are divided into 4 groups i.e. 4 pairs of heaters. Each group has its seperate thermocoupler, PID and contactor. ...
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2answers
211 views

Standard practice for earth connection when we use transformers

We bought the below device (two transformers inside a housing) from a local manufacturer and the connections was as noted in the schematic. We don't want to use the neutral from the utility. That's ...
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2answers
90 views

Why can't the circuit breaker interrupt this circuit?

I have a 3-phase input in my home. There is 127 V between any of the phases and neutral, and 220 V between any pair of phases. The electrical appliances have 127 V, and the wirings are such that the ...
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0answers
31 views

Generator internal voltage calculation

The question: The answer: However, I think the answer is wrong, it should be: Vi = Vt + IdXd = 1+ 0.971.1j = 1.46 pu So, the voltage is 1.46 * 250 kV = 365.6 kV Do you agree?
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Output phase voltage of wye-connected synchronous generator

The question: The answer: However, theta is the angle difference between the terminal phase voltage and the line current as shown in Figure 20 below So, I think the answer would be 512/12 - 47/-34....
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1answer
60 views

Power Question and Conversion

I have two power questions that would be greatly helpful. Just wanted to double check and confirm that I'm not assuming on nomenclature, but what is meant by 120/208V. My device is a UPS and is split ...
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2answers
53 views

Three-phase power and consumption: what would the bill be?

Here's a theoretical question: I have a three-phase power connection in home. I connect three devices of 1000W (1 kW) each, one to each phase. I then start them at the same time, for 1 hour. What will ...
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0answers
26 views

What is the most accurate method to calculate wire cross section according to voltage drop on AC distribution systems?

If we go for the intuitive way you should first calculate resistance of conductors based on temperature and construction properties but I don't get how to integrate that with the format of current or ...
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0answers
48 views

Calculating line currents in three phase grid

My original network looks like this: I'm trying to find the line current $$l_{l, 1}$$ the red one at very top. Here is what I have done: I converted the delta impedance circuit in the right to star, ...
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1answer
56 views

Is the current on a 3-phase AC motor (mostly) identical across all phases?

I would like to monitor long term current consumption changes over time (and derive power if I know the voltage) on a 3 phase cooling compressor for a walk-in fridge. I am not 100% sure right now, but ...
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1answer
60 views

Power of three phase rectifier

I'm confused about what type of voltage should I use to calculate the power of a three phase rectifier. For a signal like this: I've read it should be called pulsating DC. If I want to calculate the ...
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1answer
65 views

Rectified signal from three phase rectifier circuit

I'm trying to simulate this circuit This is the implementation I'm getting this output signal, that is close to what you would expect from a rectifier. In this image α = 0, α1 = π/6, α2 = 5π/6 and ...
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1answer
58 views

Three phase rectifier with thyristors not working as expected

I'm trying to simulate the following circuit with a resistive load: The control circuit provides three signals, and are the turn on signals for the thyristors: the first one (yellow) α1 = α + π/6: ...
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1answer
31 views

Three phase RL circuit voltage and current wave form?

In the case of this three phase rectifier I know the voltage for a resistive load is this (In black): With the diodes turn on/off for each point, there's a change in the line-line voltage. I think ...
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1answer
42 views

Reverse voltage for diode in three phase circuit?

I'm trying to understand what happens when a diode is not conducting in this circuit, more specifically, what's the reverse voltage applied to it? I know only one diode will be working at a time, but ...

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