# What is Dc machine: Definition and 16 Discussions

A DC-to-DC converter is an electronic circuit or electromechanical device that converts a source of direct current (DC) from one voltage level to another. It is a type of electric power converter. Power levels range from very low (small batteries) to very high (high-voltage power transmission).

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1. ### Some basic questions about a DC motor and a DC generator

Hi, The picture below shows a DC generator. The magnetic field is uniform. As the coil rotates clockwise, the right side of coil is moving downward and the left side of coil moves upward. Using Fleming's right hand rule, one can deduce the direction of conventional current in both sides of...
2. ### Why can one not make an inside-out dc machine?

In synchronous ac machines, the field is usually on the rotor and the power winding on the stator, where it's easy to cool. The field draws a small current and needs only small brushes. In dc machines, the field is on the stator and the power winding on the rotor, where it's harder to cool...
3. ### What's about no air-gap in motors?

Hi, I saw few threads here about air-gap in motors, and I wonder what if we ignore mechanical issues and make an "iron-gap" in the motor. for example: in linear motor(e.g. this cute one: https://www.physicsforums.com/threads/linear-motor-equations.794499/) if we make the tube between the stator...
4. ### DC Machine Magnetics: Torque, Back EMF & Flux Explained

I have a question regarding this part from a book on electrical machinery (the author is highly reputed in India). While teaching the motor action at an elementary level, the torque developed in the motor is explained using the equation F=Bil. But this paragraph says that the torque developed is...
5. ### I Why does back EMF in DC machines deviate from a pure sine wave?

Why voltages out of the rotating loop is constant positive and negative **Why nOT varying like sinusoidal **. Like it has a wave form of O to 2*vBL and then it maintain its value there for some time before failing to zero and changing direction. I have attach the image file from my book...
6. ### DC generator wiring basics

Given a simple DC generator with a single loop in the presence of a magnetic field such as the one below, typically, the analysis involves how each rectangular loop's terminal ends up on opposite sides of an armature housing each of the coils. The analysis is fairly straightforward to then...
7. ### Open circuit armature voltage of dc machine?

Homework Statement The book says that "the induced voltage E_a can be found by measuring the open circuit voltage at the armature terminals" Homework EquationsThe Attempt at a Solution But isn't there a voltage drop across the resistor so that they can't be equal? or is this ignored
8. ### Electric machines (looking for books)

Please help me, this is my last hope. I am an el. engineer student and i need GOOD books on electrical machinery. My proffesor is more a good repairman than a great scientist who could teach me about all the theoretical (matematical and physical) concepts which have led to modern design process...
9. ### DC machine speed/torque characteristic

Hello everyone! In the following speed-torque characteristic of a DC shunt motor, we see that if the speed exceeds a certain value, then the machine becomes a generator. I don't understand something. How is it possible for the machine to have a negative torque and a positive speed...
10. ### Air gap flux density in DC machine

Why is it that the air gap flux density is flat topped at no load. What happens to it's shape when machine is loaded?
11. ### Engineering DC Machine motor constant equation

Homework Statement Given the no-load test results of a DC motor connected in shunt to be: Speed: 3000rpm Applied voltage: 239V Field current: 0.25A Calculate the motor constant K_m, where K_m = K Homework Equations not really sure about the equations to use i have these: Km = T/...
12. ### Simple question about DC machine

Hi PF.. I am an industrial electrician (w/ a electrical engineering technology diploma) I work in a iron ore mine in northern Canada... we operate mining shovels. they are purely electric there are two motors used for hoisting the bucket, they are DC shunt wound motors. We recently...
13. ### Analyzing a 500V DC Machine for Vehicle Motion

Homework Statement Considering a 500 V, 50 HP DC machine with the following parameters, Kv=1.8 Vs/rad, tau=50 mS and ra=0.07 ohms; Bm=0 p=1.2 kg/m^3, A=2.3 m^2, Cd=0.370, Crr=0.0106, Wveh=1000 kg, g=9.8 m/S^2 Assuming the machine is connect to a single quadrant converter with a switching...
14. ### Types of commutators in DC machine

1. Types off commutator and their effect on current densit? [b.]2I want to ask how many types of commutators are there in a DC machine and what is their effect on current density..[\b] [b]3.i have been working on it for a long time and came to know tht there are two types Brushed...
15. ### Speed/field current relationship of a dc machine

Im having trouble explaining this relationship...from my graph i know that if armature voltage is held constant then the field current will decrease exponentially for increasing speed. But why?
16. ### Seperately excited DC machine question

Hi, i would be very grateful for some help... I have recently conducted an experiment and but I am not sure how to compare the values i measured with 'predicted' results (from theoretical equations). This is for the 'open circuit characteristic of a dc generator'. I set values for the...