Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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).

0
votes
0answers
33 views

electric motorcycle batteries and motor [on hold]

I am new to this world of electric vehicles but I am very interested in learning about it and I have decided to try and build one (i have zero experience) . I was hoping to find a mentor for this ...
0
votes
1answer
49 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 ...
12
votes
5answers
2k 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 ...
0
votes
0answers
27 views

Power transformer impedance

I was wondering if there are any refernces pertaining to the impedance and resistance of generator step up transformers. I have different transformers ranging from 500 to 115 kV on the HV side and 9 ...
2
votes
1answer
60 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 ...
0
votes
2answers
120 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, ...
0
votes
2answers
77 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 ...
-1
votes
1answer
154 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 ...
2
votes
2answers
355 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 ...
2
votes
2answers
97 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?
0
votes
0answers
20 views

DC Machine Armature reaction, how saturated iron core affects the armature reaction effect?

I understand the current induced in armature winding makes it to induce EMF in it but in a book there is given something I can't correlate with my understanding. "it causes no change in flux/pole ...
0
votes
0answers
36 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 ...
0
votes
1answer
45 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 ...
7
votes
4answers
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?
0
votes
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>?
0
votes
0answers
38 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 ...
0
votes
0answers
30 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 ...
0
votes
3answers
87 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 ...
1
vote
1answer
60 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 ...
1
vote
1answer
79 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 ...
0
votes
1answer
177 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^...
0
votes
2answers
57 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 ...
0
votes
1answer
64 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 ...
0
votes
1answer
58 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 ...
6
votes
1answer
337 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 \...
2
votes
2answers
284 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,...
0
votes
1answer
83 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 ...
1
vote
2answers
139 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.
0
votes
1answer
113 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. ...
1
vote
0answers
188 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. ...
1
vote
1answer
60 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 ...
2
votes
1answer
114 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.
0
votes
1answer
19 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 ...
0
votes
1answer
60 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.
-1
votes
1answer
101 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 ...
0
votes
1answer
213 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 ...
0
votes
1answer
163 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 ...
-1
votes
1answer
304 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 ...
0
votes
3answers
76 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 :...
0
votes
0answers
19 views

current path count in synchronous generators

I am trying to find the number of turns in a generator per current path (for 2 coils per slot), Wa, using this exert from Variable Speed Generators by Ion Boldea, page 429 (the equation with Wa is at ...
0
votes
2answers
98 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 ...
0
votes
3answers
423 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 ...
1
vote
1answer
85 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] ...
2
votes
1answer
70 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 ...
-1
votes
1answer
122 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 ...
0
votes
1answer
68 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 "....
0
votes
2answers
381 views

Why does torque increase with rotor current in an AC induction motor?

In my understanding, the EMF induced on the rotor of an AC induction motor induces a current, and the larger this current, the greater the rotor's torque will be. Could someone please explain: why ...
1
vote
2answers
179 views

Mechanical time constant of PMDC Motor in starting and after switching off the supply is same or different?

In my MATLAB/SIMULINK model of the PMDC motor the mechanical time constant has same value in the case starting of motor and after switching off the supply but in experimental setup there is a ...
0
votes
1answer
138 views

12V DC Overvoltage Protection

I'm trying to create a air pump system with a rechargeable battery pack. My question is: Because my air pump is a positive desplacement pump, which task is to create a vacuum in a container, will its ...
0
votes
0answers
28 views

VI curve varistor and compere between varistor and arrestor

why we need to connect arrestor in parallel with varistor in some circuit ? and we know both is work to protect against high voltage? like this pic.