Questions tagged [three-phase]

AC power with three legs run 120 degrees out of phase

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Problem with plotting of 3-phase model in LTspice

I'm trying to simulate a model of a 3-phase transformer in LTspice. My first attempt with different K values worked, but it didn't include the core saturation. Now I tried to built a new model with ...
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32 views

Balanced and unbalanced short circuit voltage of transformer

This might be trivial, but I'd like some hint on where to start. I'm calculating power flow for three-phase-four-wire distribution networks. Positive sequence and zero sequence short circuit voltages ...
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2answers
74 views

Creating a three phase current system with e.g. 70Hz instead of 50Hz

I am doing magnetic field measurements on a 3-phase cable dummy, in order to develope a distance measurement system for power cables. This is a uni research project. For a test setup I want to create ...
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1answer
40 views

Relation between speed and torque

I am a bit confused of The relation betweeen the parameters mentioned above. According to the below formula, speed is inversely proportional to Torque as: T=HPx9549/Rpm But i have been taught in my ...
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46 views

Producing a small homemade generator with reduced cogging torque

Background: I'm working on my second hobby small generator design. Particularly difficult to source are (relatively) low speed permanent magnet motors that can be run in reverse as a generator with ...
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3answers
116 views

Is it possible to model a single-phase phase-shifting transformer in LTspice/Multisim/PSpice?

As you know, three-phase two-winding transformers can produce a phase-shift between the line-to-line or line-to-neutral phasor voltages of one side and the respective line-to-line or line-to-neutral ...
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62 views

Did the induction motor strongly influence the decision of AC being adopted over DC? [closed]

I have read about using motors in industrial processes and manufacturing. I am not sure if the induction motor was invented by Telsa after the decision for AC, or if they were planning on extensively ...
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46 views

Using three-phase transformer in reverse

I'm in the US and installing a 45 kVA 480 V/208 V transformer in reverse, to power an electric car charger that requires 480 V. The secondary of the transformer is in wye configuration and I will be ...
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1answer
39 views

Correct arrangement of current sensing resistors for a BLDC motor?

I am designing the current limiting (fault detection) circuit for a three phase BLDC motor and I wanted to ask, If I have three switches on at any given time (180 degree commutation) than should the ...
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55 views

Induced voltage in the rotor of the induction motor

Given that the resultant mmf wave in the air gap of the three phase two pole induction motor is $$F(\theta , t) = \frac{3}{2}NI_m \cos(\omega t - \theta) \tag{1}$$ what's the value of the induced ...
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1answer
70 views

Can someone explain this grounding phenomenon?

I went into a conversation with an electrical engineer. Here is what was on the table: Me: How do you connect a two-phase load to a three-phase delta load? If the loads were Y-connected, then you ...
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14 views

Sharing multiple neutrals? [migrated]

Found a junction box that splices all the neutrals for 5 separate circuits. 3 on one phase 2 on the other. All 12/2 romex. Was trying to convince them to change it, but I don't have a good explanation ...
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18 views

important aspects about MOSFET in making PWM inverter

In making a three-phase PWM inverter connected to the same single-phase DBR and AC source, switching devices with real MOSFETs are going to be used. What are important aspects that I need to consider ...
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28 views

3-phase PWM inverter

I'm trying to design a three-phase PWM inverter connected to the same single-phase DBR and ac source while keeping the same load for each phase. I have the one-phase circuit but can't do the three-...
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27 views

Facing problem in converting single phase arduino code into three phase for 5 level inverter

I am making 3 phase inverter using 5 level inverter technology using arduino nano. The code i am having is for only single phase 5 level inverter but i want to make 3 phase inverter using this code ...
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31 views

How to predict KW rating and rated current when there is no nameplate on a three phase induction motor?

I came accross the following tasks during my trainee period in an electrical firm. I was provided motor with no nameplate in following conditions: When I can remove the mechanical load from the ...
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3answers
144 views

Why does this three phase induction motor have two kW ratings?

I came accross a three phase induction motor with two kW ratings written on its nameplate against the two frequencies 50Hz and 60Hz. Does the kW rating increase with frequency? Shouldn't the kW ...
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1answer
49 views

Relationship of complex load angle, voltage/current phase different and load factor

Question: Explain the relationship of the load impedance angle to the displacement coefficient cos(𝜑1) and the power factor λ at the input of the rectifier Not sure exactly what its asking for. It ...
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2answers
50 views

Three Phase AC Induction Motor - Locked Rotor and Phase Drop Questions

A few questions about three phase AC induction motors. All questions relate to a Wye connected motor, running off 120V rms (phase-neutral), each phase 120° apart. This is a pure and simple three phase ...
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2answers
92 views

How neutral wire is obtained in three phase systems?

In India, we have only 3 transmission lines which are all live. But the domestic supply includes a neutral line along with that. How we can create a neutral in a transformer? Why don't we not need a ...
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2answers
30 views

ICE-electric transmission drivetrain parameters

Pardon me if this question covers too many elements; also, originally I posted this in Engineering stack-exchange but it may be more relevant here. Basically I do not fully comprehend what would be ...
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32 views

3rd harmonic component of flux and current in Star -Star connected 3phase transformer

I wanted to understand what will be 3rd harmonic component of flux and current in following connection . Connection - Star- Star connection (with neutral on primary side only) Further description- ...
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21 views

Open-Delta 3-phase transformer kVA rating

I have a V-V three-phase transformer supplying a 50kVA balanced three-phase load. I know that the apparent power of a three-phase transformer \$S_{3\phi} = 3VI^*\$ and that of an open-delta system is \...
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1answer
48 views

Only 3 wires in 3 phase motor terminal box

I have a 3 phase motor with the nameplate below At the terminal box you have your standard 6 pins labelled u, v, w, u1, v1, w1. However, the u1, v1, w1 is not connected on the terminal block but ...
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2answers
47 views

3 phase heating control of hot water

I am looking for some help on a system which I have here. There is a temperature probe in a tank which is monitoring the temp of a liquid and the controller output is switching a 3 phase contactor on ...
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94 views

I have a 3 phase power at home, the third line is always at 220V, why is this the case?

I have a 3 phase 220V power at home and L1, L2, L3 is at 220V. When I measure the voltage using my electric meter as follows: L1 & L2 = 220V L1 & L3 = 220V L2 & L3 = 220V Yes my electric ...
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80 views

Risks of riding E-bike under high voltage power lines

I've recently experienced a small electric shock each time while I was passing under international power lines for 3 times. They transport at around 330K volts. While it didn't hit me really hard, a ...
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2answers
46 views

Change the speed of an induction motor with an additional capacitor

I have a three phase induction motor (a fan motor) that get power from a two phase power line. To start the motor I have a start capacitor. I need to change the speed of the motor to reach the 70% of ...
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34 views

Single-phase thyristor full bridge rectifier vs three-phase thyristor full bridge rectifier

For Single-phase thyristor full bridge rectifier compared to a three-phase thyristor full bridge rectifier, with regards the input current harmonics, does the three- phase rectifier have an advantage ...
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1answer
25 views

how calculate the energy use for starting a 3 phase motor until return to normal work?

for a project i must calculate the exact energy that used for start of motor until the motor return to normal work in other words how much energy use for normal work of this motor equals the starting ...
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1answer
39 views

Difference between THD equation and design circuit current

Why does the summation of design circuit current equation (Ib) start with 1 while for calculating THD the summation starts with 2?
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94 views

3 phase transformer efficiency calculation

This is an assignment. No matter how hard I try the answer is never what I expect. Here is the question: Three single phase transformers, each rated at 12 kVA, 120/240V, 60Hz, are connected to form a ...
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30 views

Three-phase rotary converter wiring questions

I am installing a 30 HP three-phase rotary converter on a 200 amp service in my home shop. I intend to run a CNC milling machine with a 15 HP motor. I am using 2 AWG wiring in 1" shielded conduit ...
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1answer
42 views

Creating a 3 phase current

For an experiment (generating a travelling magnetic field) in high school I need a 3 phase current. My school does not have access to 3 phase power. Therefore I need to generate the 3 phase power out ...
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1answer
57 views

Understanding Per Unit System

I am having issues understanding the Per-Unit System calculation. I don't come from an exact power engineering background so I hope my question is not too stupid. For the calculation of base ...
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29 views

Space vector and bias voltage

I am trying to learn the space vector modulation but I am wondering how is the bias voltage in a 3-phase system regarded by the space vector?
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2answers
49 views

Connecting a three phase drive - Should N connect with L3?

I have a simple question. I'm going to connect a three phase motor. 'Three phase source -> drive unit - > three phase motor' But between the three phase source, should I connect N with L3, or ...
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2answers
137 views

Switching power line phases with inductive load

I have one question related to this schematic: Scenario: Source 1: AC source 220VAC, 50Hz, 120º Source 2: AC source 220VAC, 50Hz, 0º If I want to switch from source 1 to source 2 or from source 2 ...
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4answers
63 views

Phase and voltage conversion

I have a hypothetical question in regards to phase conversion and transformers, more specifically on their combination. I am not a certified electrician or engineer, so I don't know what all goes into ...
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1answer
30 views

LTspice Model Stopped Working

Tried to model an equivalent circuit for a 3-phase TN-S system to model inrush behaveour. Was working for a while, and now nothing beyond the "Power Cable". Probably an obvious reason, but ...
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1answer
71 views

Bizarre problem with 3 phase WYE system

I have a weird problem with the electricity in my house. The house has a three phase municipal supply 400/230V WYE electrical system. The house is old and already I have had problems with water ...
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1answer
20 views

Testing a 3-phase ev charger on an 1-3 frequency regulator

Im currently working in an office environment developing a system to communicate over rs485 Modbus with an 3 phase EV charger. Due to the location it is not possible to get three phase power. However ...
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2answers
87 views

Simple wireless power transfer circuit question

source: https://circuitdigest.com/electronic-circuits/simple-wireless-power-transmission-circuit-diagram Above circuit is the very simple wireless power transfer circuit, but I could not find any ...
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2answers
96 views

Current Transformer in power meter

How to measure the total power in a 3 phase electrical system with one current transformer?
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3answers
63 views

Do data centers use single phase or 3 phase to power their infrastructure?

3 phase is more efficient than single phase for converting AC to DC; since after rectification stage the signal requires less regulation. Do some data centers use 3 phase power to take advantage of ...
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2answers
136 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 ...
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1answer
51 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'...
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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 ...
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1answer
44 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?
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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 ...

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