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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26 views

Formula for calculating the MMF and its harmonics of n-Phase PMSM with integral slot winding (slot per pole per phase =1 & 2)?

Data\Prerequisites: Integral slot winding full pitch winding Slot per pole per phase = 1 and 2 (two different possibilities) Number of phases : n = 3,4,5,6,7 Assume number of turns = N and current to ...
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36 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 ...
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2answers
591 views

Why do some motors have high rpm while other have low even though having same power consumption

I have seen a 500w motor which run on 1200 rpm but a 300w motor with over 10000rpm . I know using a gearbox can give required rpm or torque and torque is inversely proportion to speed but how can I ...
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42 views

Voltage Difference Between Machine Laminations

Given a lamination stack that is exposed to a transient magnetic field, how can the potential difference between the individual laminations be determined? is there a rough rule of thumb that can be ...
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175 views

Does regenerative braking, using supercapacitors, really save fuel in the case of diesel city buses? [closed]

Does regenerative braking, using supercapacitors, really save fuel in the case of diesel city buses? A 10-ton diesel bus, fully loaded, that slows down, on average, from 30 km/h to 0 km/h each ...
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31 views

Which case count as leading PF in Salient plot generator?

In the figure above we can see the location of two armature currents. In case 1, \$I_{a1}\$ is leading \$Vt\$ (terminal voltage) but lagging \$E_f\$ (excitation voltage). In case 2, it is obvious that ...
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35 views

When do the positive sequence negative sequence, and zero sequence apprea?

I have analyzed three phases current in different cases, but I am still confused about some cases. Positive and Negative sequences are appeared but not the zero. Zero sequences is appeared, while ...
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1answer
105 views

Can someone tell me what this machine is? [closed]

It has two probes on two cables. I think it might be an xray machine but I can not be sure since there is no readable info on it. Can someone please identify it?
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460 views

Tesla model 3 motor

The Tesla's model 3 uses IPM-SRM motor in the rear drive. This motor is fed by AC supply OR DC supply? Is the motor's stator is of salient pole construction OR the same stator as of the induction ...
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1answer
143 views

Why earth pin in plug is larger than the other pin?

Why main line pin is not bigger ,the work of main line pin is more important than earth line? And the flow of electricity is also pass through main line and neutral pin then why earth pin is larger ...
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349 views

Why are the poles of the stator and rotor taken differently in the picture below?

The rotor and stator in the picture below have the same orientation of flux lines yet the are taken as opposite that is flux lines leaving the stator is taken as a South Pole while flux lines leaving ...
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1answer
63 views

Are the emissions to power electric cars really better for the environment than the emissions from petrol cars? [closed]

In my country most of the electricity is generated by coal which is then in turn used to power electric cars, which I don’t think is to good for the atmosphere, is there any prof that this is better ...
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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?
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1answer
123 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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73 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
81 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
78 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
697 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
25 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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1answer
209 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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30 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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2answers
152 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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128 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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2answers
60 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
57 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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63 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
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 ...
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5answers
3k views

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
163 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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1k 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
499 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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2k 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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383 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
481 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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104 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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52 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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4k 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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52 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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76 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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45 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
127 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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128 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
102 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
1k 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
582 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
193 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
249 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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472 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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905 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,...