Questions tagged [rotor]

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Torque developed by Star Connected rotor

The current in each phase of a Y-connected rotor winding is 200 amperes. The resistance per leg is 0.003 ohm. Determine the torque developed by the rotor at a slip of 3%. I don't understand how to ...
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40 views

Why don't I get a bell curve in the torque vs rotor position plot?

I have designed a inset PMSM. I tried to plot the torque vs. rotor position plot but I am not getting a bell curve. Like at the torque must be maximum only when theta is 90 degrees. I don't know where ...
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20 views

When changing rotor current in alternators, the pf and inductive part of the current changes but the resistive part does not. Why is this so?

Given a current for an alternator $ I = I_R - jI_X $ When the rotor current changes, the excitation changes so the magnitude of the generated voltage changes. The current changes, but only the ...
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1answer
40 views

Controller of BLDC internal vs external rotor

The 3-phase permanent magnet BLDC motors come in two types, internal rotor and external rotor. Mostly the external rotor types are called Hub motors as they are used in electric bikes. Both types of ...
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4answers
481 views

Why doesn't the shaft of a running induction motor cause an electric shock?

Source: learnenginering.com Source: learnenginering.com Source: Wikipedia.org Source: Own photo. Here are some parts of an asynchronous induction motor aka squirrel cage type rotor. As clearly ...
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1answer
155 views

How do I quantify the effect of stack lamination on a stator and on a rotor of an induction motor?

Image from here: I would like to design (or to calculate the existing of) an induction motor, either 3 phases or single phase. I understand that both stator and the rotor made from a stacked-laminated ...
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1answer
284 views

How does adding resistance to a wound rotor induction motor increase torque?

I read that adding resistance to the rotor circuit causes the induced current in the rotor to be more in phase with the stator current. This produces a very small phase angle difference between the ...
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1answer
43 views

Electrical Motor filler metal for laminated stacks

Looking at several cores from failed motors some will have a filler-type material that is inside the stack of laminates. This material is almost always silvery, and it does melt relatively low, ...
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4answers
153 views

Calculate ideal unloaded rotor speed

I have the following problem: MY ATTEMPT Okay, I've found two formulas that will definitely help me solve this problem: The first is \$S=\frac{N_s-N}{N_s} \$, where \$S\$ is the slip, \$N_s\$ ...
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1answer
279 views

Induction motor starting torque and pull out torque

Recently I was doing some work on the induction motor where I found some general theory on starting speed torque curve of the induction motor. Where the theory is the starting torque will be 1.5x of ...
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1answer
276 views

Calculating Rotor Inertia or Mechanical Time Constant for BLDC Motor from Published Specs Only

TLDR - Is there any way of calculating the Mechancial Time Constant and/or Rotor Inertia and/or Run-Up Time based soley on the specs provided on this motor My end goal in asking this question is to ...
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1answer
89 views

Calculating speed of the rotor with slip

The question i'm having trouble with is: Calculate the speed of the rotor of a 6 pole induction motor with a slip of 2.2%. The motor is connected to a 230V single-phase supply. I am familiar with ...
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1answer
93 views

PMSM Rotor Design. Are these terms equivalent?

I'm working on a project with a PMSM. As I go through the literature I come across the following terms and wanted to make sure that I am getting right which ones are synonyms. Surface-mounted PM = ...
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2answers
488 views

(edit) Brushless Motor - Why does the stator burn up if the rotor doesn't rotate?

If I was to apply power to a 3 phase stator, which in turn creates a magnetic field that's projected onto the rotor (with magnets), and (in a friction-less world) would cause the rotor to rotate (...
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1answer
129 views

What type of motor is this? (photo included)

I want to make this motor work, but I can't understand what type this is. I supplied 5V DC to the terminals, but it just kept buzzing and the coils were energized. It also had some kind of circuit, ...
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1answer
199 views

What is the practical use of Laplace Transform?

I am trying to understand the electrical model of 3-phase Induction Model. The rotor of the motor is modeled as a variable resistor in s-domain. I fail to understand how that works practically. Can ...
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1answer
111 views

Can a DFIG operate in a synchronous speed?

A DFIG can operate in both sub and super synchronous modes. Can a DFIG also operate (stable) in a synchronous speed? If so, would the rotor current (as decided by IGBT switching) be DC since the rotor ...
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3answers
421 views

Apart from speed, do VSD's also alter current?

As I know it, a VSD alters the frequency to change the speed of a motor. I also understand that since the back emf of the rotor is directly proportional to the speed of the rotor, the slower the motor ...
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1answer
475 views

Working of a Doubly-Fed Induction generator (DFIG) in wind turbines

I am unable to understand how a Doubly-Fed Induction generator works (in Wind Energy conversion system)? I do not understand how the reactive power fed into the stator interacts with the rotor so as ...
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1answer
172 views

Why the rotor core losses are very tiny compared to the stator core losses in an induction motor?

Book says rotor mostly runs at speed near to synchronous due to which the relative velocity between rotor and stator magnetic field is very less. Correspondingly making rotor core losses tiny and ...
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3answers
1k views

Why rotor copper loss in induction motor doesn't change with slip

Why air gap power is consumed in R2/s but rotor copper power loss only in R2? Transformer Equivalent circuit of Induction motor: ...
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0answers
122 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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4answers
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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3answers
24k views

Finding number of pole pairs in a BLDC motor

I have a 3phase CDROM BLDC motor for which I don't have any datasheet. How can I find out the number of pole pair in the motor? Hint:-With a magnet, I could check that there are some N and S poles in ...
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1answer
947 views

Can I coil directly onto the iron cores of a stator for a basic generator?

I am constructing a very basic miniature generator (25mm diameter), the rotor has 8 bar magnets, and there will be the same number of coils, wired appropriately, in the stator. . I understand that ...
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0answers
67 views

Describe this type of rotor from a three phase induction motor?

After CNC machining the rotor, to expose the outer surface of the silicon iron, this proves to be exactly the same as the inner surface was (the one facing the core).Just plain electric iron rings ...
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3answers
75 views

IC that measures RPM mounted on rotor without magnetic field [closed]

Does this chip exist, there only seem to be hall sensors?
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1answer
716 views

Relating Hall sensor outputs to absolute rotor position (Which combination corresponds to which angle)

I have a working 6-step BLDC commutation which works based on the Hall effect sensor outputs. I would like to apply the same code to another motor, which doesnt have Hall sensors but an absolute rotor ...
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1answer
5k views

Why would a rotor get stuck on the side of the stator when the induction motor is turned on, and how to fix it? [closed]

My big fan stopped working, so I decided to dismantle it and check what's wrong with it. The problem lies in a faulty induction motor. I opened it and found out that I can easily turn the rotor ...
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2answers
2k views

what is the transformation ratio of squirrel cage Machine? [closed]

typically Induction machine also called rotating transformer so what is the ratio of stator numbers of turns to rotor number of turns (from the design point of view i.e we can't directly measure ...
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1answer
131 views

Fine tuning PID controller for non-linear closed-loop system

I am having trouble getting my PID controller to be accurate over a range of values. My goal is to input a duty cycle for a PWM wave, which controls the speed of a fan rotor. The range of possible ...
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2answers
7k views

What is meant by front and back pitch of an armature winding?

I searched the internet for these definitions and found a common definition in all websites: Back Pitch- A coil advances on the back of the armature. This advancement is measured in terms of ...
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1answer
5k views

why the stator frame of a 3-phase generator is made up of cast iron?

I don't have a good knowledge of engineering materials, so please answer the following questions with reasons. Why is the stator frame of a 3-phase generator made up of cast iron? Why is the ...
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2answers
1k views

What happens if i rotated a DC motor's rotor?

a 3V DC motor. If i rotated its rotor at a constant RPM without any DC input, what will the output current be at the terminals? will it be a constant Sine wave or DC?
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1answer
4k views

Alternator shaft speed

I am running an alternator with an electric motor (variable speed), but I do not know the shaft speed. I would like to calculate it from voltage frequency. The rotor of the alternator has 12 poles (6 ...
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2answers
82 views

DC motor exception

What happens to our DC motor if we stop motion of the rotor with our hand while motor is active? Will the motor burn? Why, what is really happening in that situation?
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1answer
1k views

Rotor current paths and lamination in an induction motor

As far as I understood, the rotor currents circulate through the aluminium bars embedded inside steel laminations. But why do they use steel for laminations instead of an insulator if the the idea is ...
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3answers
3k views

Meaning of “with respect to rotor and stator”

In the following example, when it says “with respect to stator” and “with respect to rotor”, did they mean the rotor part of the synchronous generator in both cases? Example: The excitation field in ...
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2answers
238 views

Circuit of a Rotor on an Induction Motor

Here is an equivalent circuit of a rotor on an Induction motor: Can someone explain How do we arrive at this circuit? The rotor seems to be only a disc(made of a metal) with conductors embedded near ...
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2answers
3k views

How do I modify a DC electric generator to get the same power at a lower speed?

This will be a theoretical question. Suppose that I have a DC generator, and I'm getting 300VA power from it when it rotates at 2000rpm. I want to make it run at a lower speed of about 700rpm, and I ...
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2answers
3k views

Which parts of this rotor can be made out of plastic?

I'm asked to redesign a rotor, by making as much parts of it as possible out of plastic. The issue is its weight, we want to make it as light as possible. Especially the shaft & axis of it is the ...