Questions tagged [three-phase]
AC power with three legs run 120 degrees out of phase
696
questions
0
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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 ...
0
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2answers
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 ...
-1
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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 (=...
0
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0answers
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 ...
0
votes
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 ...
0
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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 ...
0
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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 ...
0
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0answers
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 ...
2
votes
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 ...
0
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0answers
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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0answers
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, ...
1
vote
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 ...
1
vote
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 ...
0
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0answers
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 ...
1
vote
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?
...
0
votes
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 ...
0
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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 ...
2
votes
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 ...
0
votes
0answers
15 views
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 ...
3
votes
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 ...
0
votes
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 ...
1
vote
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 ...
1
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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:
...
0
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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:
3
votes
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 ...
-1
votes
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 ...
2
votes
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 ...
0
votes
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) ...
1
vote
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 ...
0
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0answers
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 ...
0
votes
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 ...
0
votes
0answers
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 ...
0
votes
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 ...
0
votes
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. ...
-1
votes
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 ...
0
votes
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 ...
0
votes
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?
1
vote
0answers
40 views
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....
0
votes
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 ...
0
votes
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 ...
0
votes
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 ...
0
votes
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, ...
0
votes
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 ...
0
votes
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 ...
0
votes
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 ...
0
votes
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:
...
0
votes
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 ...
0
votes
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 ...