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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1answer
28 views

Any good material to study types of windings, mmf and flux waves in machines(specifically synchronous and induction)? [closed]

So, I've been trying to search some good material where the basics of windings,flux and mmf waves for DC and AC machines are explained for beginners but I can't find any. Answers below would be ...
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30 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?
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93 views

Are permanent-magnet motors equally (in)efficient as motors vs. as generators?

Given a permanent-magnet motor with an efficiency of 80% that converts 100W electrical input power into 80W mechanical output power, would the motor have the same efficiency if used as a generator? ...
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19 views

AVR Excitation System and Generator in SimuLink

I am designing in simulink cooperation of synchronous machines with the grid. The main blocks are Excitation System which is AVR [link1] and Synchronous Machine [link2]. On the site we can find "...
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2answers
59 views

In 3 phase induction motor how many phase will be generated in wound type and squirrel cage rotor?

In 3 phase induction motor how many phase will be generated in wound type and squirrel cage rotor? If we consider a generator when the rotor rotates there will be voltage induced in every pole of ...
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1answer
36 views

Understanding of torque constant and efficiency of a permanent magnet motor from datasheet

I am trying to understand the efficiency of the following permanent magnet synchronous motor Motor Datasheet (note we are using the medium voltage model), and its relationship with the input voltages ...
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1answer
68 views

How brush shifting affects current distribution in dc machines?

I understand that how armature reaction causes neutral plane to shift by some angle . If brushes are placed along Geometrical Neutral Axis, then there'd be sparking during commutation as voltage ...
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1answer
20 views

Mean Free Path of Magnetic Core

I don't understand how they got the mean free paths (ls) of each leg. I know that I should be calculating the longest + the shortest paths and divide them by two, but I don't know HOW I should be ...
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If a high rpm motor is run at lower rpm, will it produce more torque?

I did the following calculations: Max current = 1.2A, Max voltage = 12V Then power = 14.4 watts = 0.019hp Rpm = HP * 5252 ÷ torque I need a torque to 2kgf-cm = 0.144 lb-ft Gives rpm= 698. Thus this ...
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23 views

Rotational voltage in induction motor

When performing dq transform on a induction motor, all axis are rotating with specific angular distance between them. If so how can the state space equation of induction motor have a voltage factor ...
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1answer
60 views

why induction motor torque oscillating?

why when start induction motor the torque oscillate before become constant, like the following matlab torque simulation graph .
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19 views

Can torque angle of motor be positive?

For any motor text say that, the rotor field follows the stator field with a certain torque angle. And in case of generator, the stator field follows the rotor field with a negative load angle. The ...
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24 views

Induction motor equivalent model (abc vs dq)

Why is the equivalent circuit of an induction motor structurally different in abc domain (link) and in dq domain (link)? I mean abc has load modeled as a variable resistance while in dq it is not. ...
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38 views

DQ transform on AC voltage source

I have a simple AC circuit made in Simulink where a dq transform is applied to a AC voltage source which is connected to a RLC load. I understand that dq transforms are used to convert synchronous ...
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2answers
141 views

Hidrogen generator - electric problem

I made an Hidrogen generator (HHO) like YouTube : https://m.youtube.com/watch?v=zq8YMON9hjA&list=PLPCtNZjqSVUhWVzuxEkzlyrz1CatH8OiF&index=29&t=504s but , it does not working at all. ...
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52 views

Find force pull solenoid

Sorry for the previous post that was wrong. I want to knowF=(NI)^2*μ0*A/2L^2 A What is the cross-sectional area? NewRef.https://www.researchgate.net/publication/...
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2answers
96 views

Automotive alternator

I have been working on a project where so called Lundell alternator plays a crucial role. I haven't got any experience with this device sofar so I have decided to study some literature regarding this ...
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33 views

What is the reasoning behind the transient circuit for a synchronous machine short circuit?

Assume that a 3 phase symmetrical short circuit occurs at the terminals of a synchronous machine working at no load and constant speeed. The machine is characterised by a field winding fed with a DC ...
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15 views

Why Backwards field rotor current are higer and of lower pf?

I have read a book in which it is written that backwards fields rotor current are higher and have lower power factor and low slip. But at low slip resistance is high as compared to forward field so ...
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2answers
59 views

Electric brushed motor for electric car project

I am using a 24v 11amp 5700 rpm motor for a single seater car project. The problem is that when i am connecting the motor directly to the batteries without any throttle or control the vehicle shaft ...
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1answer
52 views

Sources and References for Motor Selection [closed]

So, I was wondering if there is a book/textbook which discusses the issue of selecting the proper motor for a job. The type of it (induction, synchronous, DC, etc.) and mainly the nominal power of it. ...
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1answer
47 views

Power consumption for an in-wheel motor

I'm trying to estimate the power consumption of an in-wheel electric motor. I used the formula $$P = T\cdot\omega + K_m\cdot T^2$$ where T is the torque, ω is the motor angular velocity and \$...
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1answer
395 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 ...
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How do I fix the speed of a generator?

If I need to generate power at a specified frequency, then I need to make sure that the rotor of the generator rotates at a specified speed (rpm). But when I am rotating it with steam or water how do ...
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1answer
113 views

Generator Frequency

How do I calculate the kW output on a generator when changing from 60Hz to 50Hz? i.e. if I have a 70kVA generator at 60Hz producing 56kW, how do I calculate what the kVA and kW's would be if I ...
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2answers
398 views

Do resistors consume reactive power?

I encountered this problem in one of my books where the problem asked to find the power loss in the core of an induction motor. I worked through the problem and I found the current as in the picture, ...
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2answers
195 views

How is the shaft of a motor fixed in its position?

Consider for example a brushed DC motor. 1- Is the shaft of the motor (which is rotor in this case), actually floating mid-air because of magnetic field of stator? Why doesn't it fall down due to ...
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1answer
1k views

Why does a wind turbine deliver reactive power to the grid during no winds or when turbine is stopped?

An answer to a previous question explained that a turbine in stop mode may deliver reactive power to the grid. It also takes active power from the grid to run its control system, lighting system and ...
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2answers
370 views

How do designers know about kilowatt power of wind turbine generators like 1.5 MW?

Generators and transformers are always designed in kVA because designers never know about the load it will provide power to. Then how do we know the wind turbine generator will deliver 1500 kW or 2 MW ...
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2answers
259 views

What is torque-ampere ratio at electric machines? How it is related with machine efficiency?

When I am reading a journal about SRM (switched reluctance machines) it said that outer rotor design has better efficiency due to higher torque ampere ratio. How it is related with efficiency?
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64 views

EMF - DC Permanent Magnet Motor

I am using FEMM to design a dc permanent magnet rotor. I am trying to calculate the EMF that is induced to the rotor. Since each coil has a different position, the induced emf will be different. In ...
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1answer
50 views

power losses induction machine

I am totally lost in a question, how can be derived the friction losses of a induction machine based on this equation (It wasn’t given explication about these nor the bibliography/source of this ...
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4answers
3k views

Why is slip necessary in an Induction motor?

Why should the rotor of a 3-phase induction motor not rotate at synchronous speed?
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51 views

Where does come this power loss?

Regarding the next problem why is asumed that there was a power loss of 928 W>?
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58 views

What is these factor multiplying the current of the copper wires_?

I was reading some solved problems about transformers but I don’t understand how was calculated the losses in the copper. - Enunciate: A one phase, 10kVA, 2400/240, 60Hz distribution transformer has ...
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39 views

Transformer equivalent circuit values

I was given the following data about a transformer 1 \$\phi\$ 25 kVA 220/440 60Hz gave the following test results Open circuit test (440V side open) 220 V, 9.5 A, 650 W Short circuit test(220V ...
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3answers
103 views

induction machines above 500 hp?

I have been told in classroom that there are several methods (one-step autotransformer, the star-delta connection and a solid state controler) to start a induction machine above 500 hp, but what I was ...
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1answer
78 views

Speed control of DC motor

Why is the armature control method not employed above the rated speed in DC shunt motors? And similarily why is the field control method not employed below the rated speed ? I was trying to think ...
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1answer
91 views

Induction Motor working

What happens if an induction motor given with 3 phase supply is forced to rotate with synchronous speed in a) same direction b) opposite direction Please help me with the above problem. I think ...
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1answer
635 views

Locked Rotor Torque

Hi All I am try to produce a torque curve using the standard torque equation, using the parameters given by the manufacturer as in the attached picture. $$Torque =\dfrac{1}{\omega_s}\cdot\dfrac{V_1^...
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2answers
253 views

FEMM - Transformer design and frequency

I am trying to design a transformer in FEMM and I have this issue. First of all, I simulated my transformer with 0Hz frequency and the Magnetic field is illustrated in the following figure Then, I ...
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1answer
119 views

Approximate weight ratio between 50/60 Hz and 400 Hz electric machines

I need a fast (not to much elaborated) approximation figure of how lighter will be a transformer or motor designed to run on 400 Hz compared with an equivalent machine with the same power capacity ...
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1answer
162 views

How should we interpret a electric rotor in short circuit of a induction machine?

I have seen many problems that ask certain data as current or likewise, it ask for nominal conditions and then adds the condition of having the rotor in short circuit, then this would mean for numeric ...
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1answer
393 views

Doubt about the volume of the air gap in an electrical device

So for the following device: I'm trying to figure out the torque. To do that, I need the area of the gap. In the solution, it says that the gap volume is: $$2gh(r_1+0.5g)\theta$$ But the part of \...
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2answers
574 views

Why is DC motor speed and torque direction the same, whereas in a generator it is the opposite?

What’s the relation between speed and torque in a DC machine. I know it’s inversely proportional but how? Torque is nothing but twisting moment right? If torque increases then speed must be increased,...
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2answers
299 views

Why does my in-wheel BLDC motor have sinusoidal back emf (line to line) when rotated by external system?

I have an in-wheel BLDC motor with 46 poles (permanent magnet) on the rotor and 51 slots in the stator. When I used an external machine to rotate my in-wheel BLDC motor, then measuring across two ...
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2answers
381 views

why in-wheel BLDC motor have more pole than normal BLDC motor?

I am using a In-wheel BLDC Motor having poles 46 but another normal BLDC motor have less pole as 8 pole. I have searched about other In-wheel BLDC motor and it also have 42 poles.
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1answer
670 views

Why does line current become half when load becomes half of full load in a dc shunt motor?

So, suppose a dc shunt motor is running at full load. I wanted to know what happens to the torque, speed, armature current and line current when the load changes? How are these related mathematically. ...
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451 views

Meaning of motor constants for three-phase PMSM

When looking at three-phase permanent magnet synchronous (brushless) motors, \$K_T\$ and \$K_V\$ numbers are often specified. Also, controllers for these motors typically specify maximum currents. ...
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1answer
72 views

Induction Motor circuit

Can anyone please help me in understanding the problem. I am not able to figure what he is trying to ask. I know one thing for sure, this problem only checks one thing that "Induction motor have high ...