Questions tagged [three-phase]
AC power with three legs run 120 degrees out of phase
563
questions
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2answers
96 views
How can I tell if my banana fits in the banana hole?
Are all banana plugs the same? Can I use these Fluke brand banana plugs and plug them in to this Extech brand phase rotation tester? Will they fit?
What defines banana plugs anyway? Is there an ISO ...
0
votes
1answer
47 views
Need help selecting the right speed controller for a 3-phase AC motor [closed]
This a three-phase single-volt 5-HP AC motor salvaged from a treadmill with a busted controller board.
The goal is to salvage the treadmill. Originally I was trying to repair the controller board.
I'...
2
votes
4answers
4k views
Need help identifying wires on 3-phase single-volt AC motor (6 leads)
I'm far from an electrician. Just a guy trying to get some new life out of an existing piece of machinery.
See the image below, this 5HP motor comes from a heavy duty commercial treadmill. Based on ...
1
vote
1answer
41 views
Why were the phase currents taken instead of voltage as inputs in the space vector moduation method?
Why is it that the currents (ia,ib,ic) are taken as inputs, instead of voltages (va,vb,vc), when at the end, you need to create 3 phase stator voltages for the rotor to catch up with?
0
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0answers
43 views
Unsure if motor starter (contactor + overload) is needed instead of normal solid state relay
I am designing a system with several pumps ranging from 0.5 to 1.5 HP (all single phase) and am unsure of what kind of circuitry I need. I researched different motor contactors and overloads I could ...
1
vote
1answer
46 views
What governs the output voltage of a three-phase generator?
If you have a three-phase generator (or motor run as a generator), what part of it governs the output voltage? For example the speed at which you rotate the shaft governs the output frequency, but ...
3
votes
1answer
66 views
Is it safe to bundle together 380V cable + 24V signal cable + network cable?
I have the following cables between two machines:
380V 3-phase power cable
24V signal cable
EtherCAT cable
I would like to create an interface using a modular connector such as the one in the ...
1
vote
2answers
30 views
Finding the power dissipation in a wye-connection given resistors
The problem that I'm attempting to solve is the following:
Three 1000 Ī© resistors are connected in Y to a 200-Vac line. The power dissipation of the Y combination would be _____W.
a. 42
b. 41
c. 40
d....
0
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0answers
35 views
Shoot through problem in 3-phase BLDC controller circuit
I have designed a 3-phase controller for a BLDC motor. I am checking one side of the bridge with a Pico-scope for shoot through. The wave-forms below are indicating that i am getting shoot through, ...
0
votes
1answer
33 views
DC unregulated power supply
I want to make a 70 VDC power supply, output unregulated with +/- 10V variation allowed.
I also want 50 A current from it.
My input can be 3-phase 380 V mains supply.
I cannot think of a 3-phase ...
1
vote
0answers
27 views
3 phase power systems
why does a phase ground fault in an impedance grounded 3 phase system lead to variation of voltage in healthy phases but this variation doesnāt happen in solidly grounded systems?
I was thinking about ...
4
votes
1answer
59 views
3 Phase motor changing rotation on startup intermittently
I have a total of three 3-phase floating fountain aerators. Last year they functioned properly. This year when I connected them, two of them were running in reverse and 1 was running forward. All ...
0
votes
2answers
46 views
Relay for 3 phase equipment
First of all - I am just reading up and will not perform any real life installations! ;-)
If you have some 400V 3 phase equipment (e.g. a 3 phase motor), what is the practice for controlling the ...
0
votes
1answer
45 views
Single and 3-Phase Load Calculations
I have a probably obvious question about powering single phase loads from two legs of a 3 phase supply and how this impacts current draw calculations. This is something that is commonly done in my job ...
0
votes
1answer
39 views
Understanding voltage sampling rate of induction motors
Why it is required to have a sampling rate of at least 4kHz when sampling the voltage waveform of a three phase induction motor?
I find most research papers use 4kHz but they don't state why.
I want ...
0
votes
1answer
24 views
Wall Voltage in 3Phase
I have a relatively simple question on the grid voltage. When we say the voltage from the wall is 220 Vrms is that the line-line voltage or is that the phase voltage. ie are the two output lines from ...
0
votes
1answer
89 views
Simple 300-400VDC/100A power supply for EV charging from 400V 3-phase/32A
I would like to purchase or build a simple AC-DC power supply, with 400V/32A 3-phase input, and DC output adjustable (by a microcontroller which I would add) between 300-400VDC and upto 100A (not ...
0
votes
2answers
31 views
3-Pole Circuit Breaker with GPIO
I'm starting a small project involving 3-pole circuit breakers and 3-ph motors. There's this custom built machine with multiple 3-ph motors, each connected to circuit breakers. The purpose of the ...
0
votes
1answer
25 views
How to find the 120 degree phase angle in a single layered lap winding of a synchronous machine?
Ok, so I have a 4 pole synchronous machine with 24 slots meaning each slot has a phase difference of 30 degree with respect to each other.
1)That means pole pitch is 180 degree for a full pitched ...
1
vote
2answers
59 views
3 phase heating elements
Is there a simple way of calculating the power (kW) of a 3 phase heating element?
I have 3 elements mounted in a pack and inserted into a tube and there are 12 tubes, so 36 elements in total. They ...
0
votes
3answers
86 views
How to run a DC device through 3 phace 400V AC mains?
So I need to put a wifi antenna on farmland, the issue is that the antenna needs 12V DC powered over Ethernet and the only power source nearby is a 3phase 400V AC one...
So is there something like a ...
0
votes
1answer
37 views
3-phase inductance calculation homework
This is a homework question where i am stuck. Please help me out in this:
Three similar impedances are connected in star across 2000 V, 50 Hz three phase
supply. Power absorbed is 300 kW. ...
0
votes
2answers
131 views
Three phase system questions
I have been trying to solve homework questions on three phase systems but I am got stuck in two questions while solving solving them.
Three similar impedances are connected in star across 2000V, ...
1
vote
0answers
39 views
Why does a rotating magnetic field's frequency decrease, if we increase number of poles (induction motor)?
I absolutely don't understand it and drives me crazy. I've found several sources, in which there are shown images and animations about how two or three phase electric current generate rotating ...
0
votes
0answers
19 views
When should we use \$V_L=V\$ when we prove \$P^1_{LOSS}=2P^3_{LOSS}\$.?
The book said when the transmission power and wire resistance of both one phase and three phase are the same,the power loss for one phase system is equal to two times power loss for three phase ,that ...
0
votes
2answers
33 views
The problem when i proved \$3S_Y=S_\Delta\$ by using \$S=I^2 Z\$ in three phase circuit
There is the proof about \$3S_Y=S_\Delta\$ in lots of books
I have other way to prove the \$3S_Y=S_\Delta\$,however,there is a problem in my proof,but i don't know where am i wrong
As we can see the ...
1
vote
1answer
92 views
Voltage notch behavior
I am using software to simulate and learn more about 3-phase semi-conductor rectifiers (using SCR.) I also learn about the voltage notches due to the possible overlap between the SCR commutation. If I ...
0
votes
1answer
33 views
In what condition,we can have \$P_{\Delta}=P_{Y}\$,not \$P_Y=\frac{1}{3}P_{\Delta} \$
The power consumption of three phase circuit, which is connected with \$ \Delta\$ type, is \$3000W\$,now if we modified it with \$ Y\$ type,what is the power consumption of this circuit?
The answer ...
1
vote
2answers
65 views
What are the standard PWM output signals that a microcontroller should generate for 3 phase motor control?
I am programming a FOC 3 phase motor controller on a Teensy4. The motor will be driven by 6 MOSFETs and a gate driver IC for the MOSFETs.
I have looked though the data sheets for many different gate ...
2
votes
2answers
86 views
What does this symbol mean? And I have some basic problems which the book didn't mention
A power system book asked me this question, but honestly I don't understand the circuit of question and the solution which author provided.
Question:
There are 3 primary currents, \$I_R,I_S\$,and \...
0
votes
1answer
36 views
where am i wrong in my calculation?why is \$V_{bc}=220ā 120°-120°=220ā 0°\$,not \$V_{bc}=220ā -120°-(120°)=220ā -240°\$
A three-phase Y circuit with positive sequence (abc),now if \$V_{ab}=220ā 120Ā°\$,then what is\$V_{bc}\$,and \$V_{ca}\$ ?
i thought Y circuit with positive sequence means \$V_{ao}=220ā 0Ā°, V_{bo}=220ā -...
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0answers
64 views
Windmill 3 Phase AC control PCB
I've created a PCB for my newly built 3D printed Windmill. Now I am not entirely sure about all the components and the way they function, so I'd like to have your opinion on the circuitry before I ...
0
votes
1answer
43 views
Three Phase Rectifier Question (student)
I am new to this forum. I am an Electrical Engineering student working on a project. I am using Matlab Simulink/Simscape to perform simulations.
Currently, I am working on a three-phase rectifier. (...
1
vote
0answers
35 views
Rotating magnetic field discrepancy
This may be a noob question
Lets consider a balanced 3 phase supply namely
\begin{align}
R&= V \sin(x)\\
Y&= V \sin(x-120)\\
B&= V \sin(x+120)
\end{align}
At a neutral point we would ...
3
votes
2answers
77 views
Step down 3 phase 2kV AC to 3-12V at modest current (5-20mA max)
I'm looking for a way to step down 3 phase, 2kV AC power to 3-12V DC. I do not have a neutral, just the 3 phases and ground. This will be entirely isolated, nobody will be anywhere near this thing. ...
0
votes
0answers
28 views
back to back SCR firing circuit
I am trying to design a 3-phase soft start circuit.Are these two circuits different?
My PCB design and RC snubber between anode & cathode is based on the second one.I want to make sure my circuit ...
0
votes
0answers
31 views
Control 3 phase load with microcontroller
I am designing a circuit to control a 3 phase resistive load (400V & 30A). The idea is to control the circuit with a microcontroller io. Since it will switch very often (1 Hz aprox), i decided ...
-1
votes
2answers
46 views
Will this 3-phase 208Y/120 setup work [closed]
OKAY...electrician I had out recommended the following setup to supply 3-phase wye 208/120v off of 240V single-phase. My device is pulling 30 amps, and my entire load is about 15KVA. It's impossible ...
2
votes
2answers
72 views
Polyphase multivibrator (real vs SPICE simulation)
i have a following schematic for three-phase multivibrator:
SPICE simulation shows that it should work (11 volts peaks on collector nodes):
However, when i make this circuit on breadboard it does ...
0
votes
2answers
70 views
Converting single-phase 120 V or 240 V into three-phase 4-wire 120/208 V
I am needing to convert either 240 V or 120 V single-phase into 120/208 V three-phase 4-wire. The load needed is 30 A. My panel can supply up to 100 amps, so the amperage isn't an issue.
I've looked ...
1
vote
1answer
67 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 ...
1
vote
1answer
22 views
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 ...
0
votes
1answer
40 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.
0
votes
0answers
16 views
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 ...
1
vote
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 ...
5
votes
5answers
2k views
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 ...
4
votes
1answer
109 views
“Black box” transformer: Y-Y, Y-Ī, or Ī-Ī 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 ...
0
votes
2answers
70 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 ?
0
votes
0answers
23 views
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 ...
0
votes
1answer
53 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 ...
