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Questions tagged [electric-machine]

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

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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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why the mmf created by armature current in dc machine is triangular in nature?

Why is the mmf created by armature current in dc machine triangular in nature? I have read but not understood. the graph's picture is also being attached here.
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2answers
61 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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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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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
55 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
45 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
40 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
161 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
72 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
179 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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96 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
307 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
358 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
136 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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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
47 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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2k 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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1answer
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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44 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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33 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
90 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
66 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
87 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
281 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
94 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
72 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
91 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
357 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
390 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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1answer
149 views

Why my In-wheel BLDC Motor have sinusoidal back emf (line to line) when rotate by external system?

I have In-wheel BLDC motor having 46 poles (Permanent Magnet)on rotor and 51 slot in stator. When I used an external machine to rotate my in-wheel BLDC motor, then measuring across two phase back emf ...
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2answers
198 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
292 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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259 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
68 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 ...
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1answer
128 views

Tranformer Output waveform

If input to a transformer is square/triangular, draw its output voltage waveform. This problem was asked in one of my recent interviews, please help me with this problem.
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1answer
23 views

Transforming from abc reference frame to the qd0 variable reference frame?

I have been working on transforming variables from the abc reference frame to different qd0 frames of reference, such as the stationary reference frame, the synchronous reference frame, and the ...
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1answer
84 views

How to start a cage induction motor when load torque is greater than starting torque? [closed]

How to start a cage induction motor when load torque is greater than starting torque ? Please help me with this problem.
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1answer
136 views

Why can't we use synchronous motors in fan? [closed]

What type of motor is used in wall mounted fan ? Can synchronous motor with damper winding be used in the same ? I know single phase induction motor is used in fan. But I am not able to figure out ...
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1answer
311 views

Does leakage reactance of transformer depend on quantum of load?

In a single phase transformer, considering copper losses and core losses, I want to find whether the leakage reactance is affected by change in load on the secondary? I was unable to find an answer ...
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1answer
260 views

Universal motor as DC generator

I want to use universal motor as a DC generator. The motor specifications are 180 Watt 230 V 10000 rpm When I supply the motor with 3000rpm it gives 1.5V. I thought it was rpm problem but when I ...
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1answer
429 views

Right hand rule for clockwise and counter clockwise direction [duplicate]

If the conductor 'CD' rotates in clockwise direction in the figure, voltage will be induced on it. What will be the polarity of the voltage on terminal of the conductor 'CD' when the conductor rotates ...
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3answers
87 views

Induction motor - d-q model

I would like to simulate an induction motor in Matlab/Simulink using the d-q model. I have found a paper that describes the whole procedure but I have this problem. I am trying to create this block :...
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2answers
109 views

Capacitor Array calculation to simulate high-voltage Regen in Electric Vehicle [closed]

Good morning group, I was asked something of a puzzle: We currently have an experimental EV car powered by a large nickel-salt battery. With the ignition on and foot off the 'gas', the battery shows ...
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3answers
552 views

DC Machine Ouput Voltage Waveform

I am struck in the above problem. The things I was able to figure out are It is a DC motor Direction of effective flux [Armature flux + Main Field Flux] due to the brush shift But I am still ...
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1answer
147 views

DC Motor Problem

I am really confused with the above problem. The equations which I was able to write are Ea1 = Vt - RseIa1 = kphi1*wm1 Ea2 = Vt - 0.5*RseIa2 = kphi2*wm2 phi1*Ia1 = phi2*Ia2 [Torque is constant] ...
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1answer
84 views

DC motor back emf and supply voltage

In this question the solution manual takes Eb as 250v and solve it to get the torque. How's that possible ? How can one takes the supply voltage as Eb? If there's something i don't or i didn't get ...
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1answer
157 views

mmf distribution in rotating electrical machines

we have known in ABC sequence in three phase system,phaseA leads phaseB by 120 electrical degrees, but in mmf vector of electrical machines,mmf vector of phaseB leads mmf vector of phaseA by 120 ...
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1answer
98 views

DC Motor : Torque relationship to speed

In Matlab/Simulink there is an example of a DC Motor (power_dcmotor) I can not understand how it converts the speed w (rad/sec) to Torque TL (Nm) It says:" Torque is proportional to speed; TL=Bl*w "....