# Questions tagged [electric-machine]

Electrical Machines are Electro-Mechanical energy converters. They maybe classified into motors (electrical -> mechanical) and generators (mechanical -> electrical).

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43 views

### What happens when an external resistance is placed in series with the generator armature circuit of a DC shunt generator? [closed]

I am unable to find any proper explanation .Plz help
79 views

### Does an electric motor benefit by being given a rest?

Will the following two scenarios give different results on the wear/safety of a consumer-grade electric motor: A: Run motor for 12 hours/day for 20 days B: Run motor for 24 hours/day for 10 days (In ...
917 views

### What happens if the primary and secondary side of a transformer are short circuited mistakenly?

I have described the condition in the transformer picture I have attached. Will the transformer still function in this condition?
2k views

### Will an AC series motor work with DC supply?

I have read that a DC series motor can be operated using AC supply, but there will be excessive heating in the core and yoke and also a low power factor. So, construction is modified to have laminated ...
33 views

### Is the orthogonal spacing of dq axis of AC motor with respect to electrical or mechanical angle?

In FOC of AC machines, we try to align the stator flux to Q axis and maximize the value. The idea behind this logic is when rotor flux and stator flux are orthogonal, we generate max flux. But is the ...
18 views

### picture of dq axis in multi pole motor

How does the dq axis of multi pole motor look like? Typically online images search show dq axis for motor with one pole. Consider a 4 pole stator PMSM motor. Will there be multiple dq axis for each ...
41 views

### Symmetrical Components - Three-phase D-Y transformer with unbalanced voltage and loads

I have a Delta-Wye transformer, N1/N2 = 4, and am trying to solve the circuit below, with 120VAC applied to terminals VAB only. On the secondary I have 1 ohms connected between a-n and 5 ohms between ...
5k views

### Why are there no “even” harmonics in AC machines?

Why are there no "even" harmonics in AC machines? In Chapman's book, he says it's because of symmetry of the flux density wave but I don't get it...
47 views

### Generating Electricity: Stator Help

I am trying to prototype an electricity generation stator with a magnet in the center. I have zero background in any of this but I have an interesting idea that likely has not been done before and yes ...
368 views

### How can the armature current of a DC shunt motor be zero at no-load?

I have seen the mathematical explanation of this explained using back EMF, where the back EMF would equal the input voltage and hence the armature current would be zero. But I'm unable to understand ...
82 views

### How to set solver for control loop simulation?

I have been developing a simulation of the field oriented control of the three phase squirrel cage induction motor (control is oriented by the rotor flux). I have been using the Xcos which is an ...
53 views

### Confusion - ideal transformer on load

When there is no load connected to the secondary, E is equal to U, and no current flows in an ideal transformer. Now if we connect a load on the secondary of a transformer, the primary will draw a ...
184 views

### Induction generator

I have an induction generator on the same shaft with induction motor. Both machines are same (have same nameplate: $U=400\,V$, $f=50\,Hz$, $n=1435\, rpm$, $P=9.3\,kW$, $\cos(\phi) = 0.90$...
18 views

### How does the shunt mmf in a long-shunt compound DC motor remain the same?

In a circuit model like this, the textbook says that the shunt mmf is the same for no-load and fully loaded conditions of the motor. How is this possible when the armature current (Ia) changes?
49 views

### DC Motor power diminishes quickly

I have an n20 DC motor which has a gearbox with a 55mm m4 threaded shaft (see image below for visualization of the motor). I'm compressing a spring with this motor, so the motor needs to work ...
29 views

### Zero sequence component in unbalanced faults rotation

I am trying to understand the physical/practical meaning of the zero sequence component, I referred to some books. however, I am not sure is me or are there different interpretation of the zero ...
31 views

### Is the zero sequence component considered balanced?

how is the zero sequence component is balanced while the three vectors are inphase and not displaced from each other by 120°? Isn't the definition of a balanced system is one in which the magnitudes ...
378 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?
85 views

### Diagram of electrostatic precipitator

I was reading an article about working of ESP at this website: https://www.electrical4u.com/electrostatic-precipitator/ Though the explanation was nice, I couldn't understand what the diagram conveys....
3k views

### Could a significant amount of electricity be generated from public hand-operated generators?

So imagine you're at a bus stop at a train station. You're bored and have got nothing to do. So you see a big crank-handle sitting there doing nothing, and because you're bored, you decide to spin it ...
34 views

### Armature and terminal voltages in DC machines

In the below page I am trying to grasp the way the terminal voltage and armature voltage are related to each other. Below is my attempt to understand their relation: Do you agree with my ...
46 views

### Motor vector control and parameters estimation

Vector control methods require good estimation of magnetic flux. In Direct Torque Control it would vector of stator flux. In order to estimate it properly one has to know motor parameters such as ...
6k views

### What is meant by front and back pitch of an armature winding?

I searched the internet for these definitions and found a common definition in all websites: Back Pitch- A coil advances on the back of the armature. This advancement is measured in terms of ...
39 views

### Steady State speed of rotor in following doubly excited system

I'm trying to analyse following system - A three phase armature winding on stator and on rotor field winding and both stator and rotor are cylindrical . And armature winding is connected to a three ...
61 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 ...
82 views

### Voltage build up in induction generator and its working principle

I had some doubts while reading about working of self excited isolated induction generator . If principle of operation of self excited isolated induction generator is similar (in a sense that in ...
49 views

### How to predict which machine will act as motor or generator in Hopkinson's test?

Is there any way to predict which machine will act as a motor and which acts as a generator before applying the supply voltage? I cannot find a way to predict what will be the behaviour(motor or ...
389 views

### Starting torque of series vs shunt DC motors

Recently, I read that starting torque of series motors are much higher than shunt motors. I try to find out what is reason behind it and I get to know that this is because in DC series motor torque is ...
82 views

### Confusion in magnetic neutral plane of DC machine

I was reading book Electric Machinery by Chapman and in topic 'Armature reaction ' It is written that "The magnetic neutral plane is defined as the plane within the machine where the velocity of ...
97 views

### Behaviour of flux in DC motor

In given figure if we assume both sides (up and down) with equal number of coil turns (N each). And we wound(which generally we do in DC motor) coils such that they create flux and form a North-South ...
56 views

### Analysis of three phase star star connected transformer

What is going on this circuit(below) and what would be current measured by ammeter(zero or non zero)? Description- These two transformers winding are star star connected and a balance sinusoidal ...
35 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- ...
28k views

### What is the difference between 50/51N relay and 50/51G relay [closed]

On electrical engineering field of power distribution. When it comes to ground fault detection on solidly grounded or low resistance grounded transformers. When do we use 50/51N relay and 50/51G, do ...
382 views

### Voltage and current rating of electrical systems

Why voltage and current ratings of almost all electrical systems are RMS value of voltage and current not peak value of voltage and current? First I thought maybe because mostly ac input is sinusoidal ...
92 views

### Contradiction in solution for ideal transformer

I was trying to analyse an ideal transformer with one ideal independent voltage source on each winding. I got a relationship between those voltage sources but it contradicts the fact that both voltage ...
303 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 ...
47 views

### Why does wave winding not need a voltage equalizer?

I understand that lap winding needs a voltage equalizer to balance the voltage at different points. However, I could not understand why wave winding does not need one (according to the textbook "...
50 views

### Why duplex lap winding has twice as many current paths as simplex lap winding?

I found the statement of question on page 346 in the book "Electric Machinery Fundamentals, fifth edition" written by Stephen J. Chapman. When I searched for how duplex lap winding looks ...
144 views

### Unexpected behavior of the Luenberger observer for three phase induction motor

I have been developing control software for three phase induction motor. The control software will implement the field oriented control algorithm. The considered algorithm is oriented to the rotor ...
46 views

### Explanation of v curve of sync machine

I am trying to understand the v curve of synchronous machine. Particularly, the point that changing field current can put the machine in leading or lagging mode. I am trying to get an explanation to ...
47 views

### What electrode material can I use for electrical discharge machining? [closed]

Can I use an electrode made of melted soldering wire in electrical discharge machining (EDM) instead of copper or graphite? I think it is very easy for me to make electrode by using melted soldering ...
100 views

### what does nominal numbers of electrical machines mean

I got confused about rated numbers of generators and motors like rated voltage and rated power . I know nominal numbers of electrical machines are numbers which the machine is designed to operate but ...
8k views

### Why starting current in star-delta starter becomes 1/√3 times that of DOL starter?

I have seen this statement in a question paper. I was asked to prove it but I can not find the logic.
77 views

### How to find rated voltage of a machine?

I am trying to understand what a rated voltage/current/power mean for a machine. when I google it, I typically get information on how to find it from nameplate, but I am trying to understand it ...
201 views

### What are the two sensors doing in the automatic bread production line? [closed]

I want to know what is the name of these 2 sensors and what function they perform Some of you were complaining about the picture quality. It is the highest quality image I can get. Also these sensors ...
68 views

### Rotor Current and Torque Producing Current in Induction Motor

Is rotor current of an Induction motor always same with torque producing current? In torque equation of Induction motor, there is also one factor called rotor power factor. if rotor current and torque ...
27 views

### How to determine transform angle in field oriented control of three phase induction motor

I have been developing a control software for the field oriented control of the three phase induction motor. I have studied a lot of application notes and literature about this topic. Based on that I ...
406 views

### How does this old fan regulator circuit work?

I was on the lookout for an old fan regulator. I had heard that its power consumption was constant at all speeds. I could lay my hands on this 1970 regulator. It appears to be a transformer with ...