# 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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### 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 ...
771 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.
1k 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. ...
593 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. ...
78 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 ...
774 views

### Transformer 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.
111 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 ...
237 views

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### 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 ...
1k 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 ...
863 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 ...
915 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 ...
143 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 :...
133 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 ...
1k 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 ...
330 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] ...
132 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 ...
248 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 ...
561 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 "....
1k 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 ...
668 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 ...
404 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 ...
38 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.
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### Induction generator

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

### Do stator windings on a permanent-magnet synchronous three-phase ac motor have sinusoidal distributions?

In motor-drives textbooks (e.g Ned Mohan's Electric Motor Drives), the text states that the stator windings on ac machines (e.g. PMAC three-phase motors and induction machines) are, in theory, ...
459 views

### using inductor in series with a psc motor

I'm trying to reduce a PSC electro-motor rpm to about 80% to 90% of it's nominal speed. It is attached directly to a centrifugal fan and a mechanical approach is not possible. The ratings are: 450 W, ...
174 views

### Electric Vehicle motor [duplicate]

Among 3 phase induction motor and DC brushless motor which motor is preferable for electric vehicle application ? Why?
144 views

### Disconnecting the load from a synchronous generator

How is the terminal voltage of a synchronous generator affected when we disconnect the load ?
70 views

### What modifies the speed of fans? [closed]

I remember the maximum speed that my ceiling fan could offer me on a sunny day when it was new.But after 2-3 years of usage the maximum speed that my fan offers have reduced a lot.Even when the ...
7k views

### How does the speed of a synchronous generator changes with load?

When the generator is rotating at rated speed and let us say that the load decreases then the mechanical torque will be more than​ the electrical torque which will lead to increase in the speed of ...
49 views

can i control induction motor theoretically that it work on -in rated conditions- 3 phase supply but also it can be adjusted automatically by means of control to work at condition of unbalance or 2 ...
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### Brushless AC generator types and their winding

It is possible to make odd number of poles in the three phase exciter winding of brushless AC generator?
489 views

### Can over-excited synchronus motor operate on lagging power factor?

All of the Electric Machines literature I'm using states that over-excited (back emf E> supply voltage V) synchronus motor will operate on leading power factor (one of them states that it may also ...
4k views

### What's the difference between the term 'Device' and 'Machine'? [closed]

Limiting the question only to the electrical domain. Calling AC machines as ac device mean the same or there is a difference in the terminology.
141 views

### Is it necessary to protect old devices against “new” 230V?

So, i was recently listening to old automatic music playing machines. These are devices from the year 1910 +/-. They are most likely purposed for 220V European power net. To me, most of the machines ...
347 views

### What does a commutator do in dc machines?

It's my exam and in need help I am sure it's reversers current and I don't know my english lecturer say it's no it's provides current I need help please
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### Total copper loss in parallel operation of dc generator

While calculating total copper loss of two dc generators connected in parallel which is valid approach? calculate resultant resistor of two parallel connected generators then use ohmic loss formula ...
155 views

### Why is MCCB 1000Vdc for photovoltaic?

I want to install MCCB for 750Vdc supply in traction application (Light Rail Transit). After finding some 750Vdc MCCBs, I looked for 1000Vdc MCCBs. All the 1000Vdc MCCBs are intended for photovoltaic ...
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### How to find out the torque constant of BLDC motor?

I am working on BLDC(Hub) motor for electric vehicle application. In my project i want to control the speed using disturbance observer. For the implementation of disturbance observer there is a ...
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### Motor Flux in Wb

I'm trying to simulate a squirrel cage motor using asynchronous machine SI units in simulink The problem is when I view stator Flux(both q and d) its unit is in V.s (volt second which is used for ...
818 views

### How to calculate the required torque or HP of single phase induction motor to carry a massive object?

I need to know the power of a motor in Hp required to move a vehicle of about 300 Kg. The vehicle is equipped with gear assembly and required to run at 20 to 25 Km/h. The electric motor that is i used ...
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### Transformer Leakage Inductance and power factor

How does transformer leakage impedance affect power factor? Or how does the X/R ratio of the transformer change the power factor ?
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### Transformer Ratio

what if we energize 50 Hz h.v side of the transformer with 40Hz, is the transformation ratio don't matter? Suppose 400/200, single phase transformer which is designed to operate at 50Hz. If you ...
845 views

### How does rated horsepower compare with input power?

If I look at the motor specs, it gives a rated HP: 1 HP @ 2740 RPM & 42.6 Amp, 1.91 ft-lb. My end goal is to get torque as a function of time, but I cannot remove it from the machine. I can ...
302 views

### Transformer Designing

Why don't we keep low voltage winding of transformer at one loop and adjust the rest of the circuit accordingly? Like in clamp meters. Also is there any software where I can model unorthodox shapes ...
15k views

### How to measure electric motor torque?

I need to measure torque output of a PM DC electric motor. My plan was to use a current clamp to log the current vs time, a voltmeter to measure volts vs time, and an encoder to log rpm vs time. ...
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### Do I need an UL approval if I build a machine and use it in my own company?

Do I need an UL approval (or any test lab) if I build a machine and use it in my own company? Where can I find a legit documentation on this subject.
672 views

### Series Wound DC motor Runaway when going downhill

I understand that Series Wound DC motors are used in traction applications like golf carts . and that these motor suffer an effect called runaway ( if no load is applied the motor increase its speed ...