What is Dc motor: Definition and 321 Discussions

A DC motor is any of a class of rotary electrical motors that converts direct current electrical energy into mechanical energy. The most common types rely on the forces produced by magnetic fields. Nearly all types of DC motors have some internal mechanism, either electromechanical or electronic, to periodically change the direction of current in part of the motor.
DC motors were the first form of motor widely used, as they could be powered from existing direct-current lighting power distribution systems. A DC motor's speed can be controlled over a wide range, using either a variable supply voltage or by changing the strength of current in its field windings. Small DC motors are used in tools, toys, and appliances. The universal motor can operate on direct current but is a lightweight brushed motor used for portable power tools and appliances. Larger DC motors are currently used in propulsion of electric vehicles, elevator and hoists, and in drives for steel rolling mills. The advent of power electronics has made replacement of DC motors with AC motors possible in many applications.

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  1. kostoglotov

    Which data set should I trust more?

    Homework Statement Control systems subject. Have a DC motor setup on a difference op-amp, then with gain, and the axel moves a wiper on a pot used for feedback. I understand the concepts reasonably well enough to complete the assignment. I'm using MATLAB scripts to approximate parameters...
  2. Cocoleia

    Conservation of Power in the armature circuit of a DC motor

    Homework Statement I am asked in a lab report to explain the conservation of power in the armature circuit of the DC motor. Homework Equations This is the data I have acquired: The Attempt at a Solution I have been reading around, and I have learned somewhat about the Armature Copper Loss...
  3. H

    Four carbon brushes for a DC Motor- what are they for?

    Hi in every theoretical explanation of any kind of DC motor there's always a split ring commutator and two brushes like in the following pic then when it comes to my motorbike/car starter motor rebuild the real thing in practice is different- see the following pic with four carbon brushes- two...
  4. F

    Static Electricity and dc motor

    If take a simple dc motor and connect the negative side to let's say a insulated metal plate. The other side directly to ground and you then turn the shaft of the motor. Would you force all of the free (loosely using all) electrons in the insulated metal plate through the motor to ground giving...
  5. S

    Engineering DC motor differential equation

    This question involves finding the transfer function for the system, but I first need to get the differential equations correct. Have I set up the gearbox correctly?
  6. D

    Diagnosis of large brushed DC motor

    Hi everyone, just found these forums and had a look around, there's some great info here! I usually deal with the run-of-the-mill industrial three phase motors so this is not my strong suit so please bear with me here. I have a large DC motor here that was brand new but failed after about 2...
  7. C

    Physic project -- DC motor with electromagnets

    1. The problem statement, all variables and given I do not have a clue where to get the information to built a DC motor with four electromagnets Homework EquationsThe Attempt at a Solution
  8. MikeTownsend

    DC motor voltage recommendations for a bike and power tools

    I have been working on some projects, I build a glass grinder, faceter with a 120v induction AC motor. Its not possible to effectively change the speeds with electronic controls being a single phase motor. It is using belts and pulleys for now. So I am wanting to build several tools, rock...
  9. A

    How to calculate large DC motor efficiency?

    What are the two methods for calculating large DC motor efficiency ?
  10. Nick Goodson

    DC Motor Speed Increases Under Load - Modeling w/ Simulink

    Hi, I am modelling a DC motor using Simulink. Under no-load conditions, I get a max speed of 180 rads/s, but under load, the speed goes up to 290 rad/s, although takes longer to reach max speed, acceleration decreases. I have a mechanical background so don't know much about motors, but would...
  11. B

    DC Motor Controls: Get Help for Layman's Terms

    Okay, this is probably going to be way below your pay grade, but bear with me because I know nothing about electric motors except that you plug them in, turn the switch, and they work. I've seen some instances where people have taken DC motors from treadmills and used them to power lathes and...
  12. B

    Is this a valid way to measure the Back EMF of a DC motor?

    While the motor is spinning, I measured the voltage (Vrm) across the motor by connecting the two probes from the multimeter to the two terminals of the DC motor via alligator to alligator banana cables. Since the current was fairly constant, I could ignore the inductance. So, no voltage across...
  13. B

    Is the torque constant of a DC motor the same regardless of voltage?

    Hi, we know that the speed varies inversely with the torque. The more the torque, the lower the speed. From torque-speed curve, we can calculate the slope. When the applied voltage increases, the straight line shifts upward while when the voltage decreases, the straight line shifts down. How...
  14. R

    DC motor running in reverse after repair

    Hi all, so my mercury 25 outboard starter was starting to give it up. I took it apart, and yup, the brushes were badly worn. Well, I have several generic brushes kicking around, so I simply swapped them out. Very simple operation. And yet after assembling the damn thing, it now runs backwards...
  15. Manoj Sahu

    Why DC series motor should not be started without load?

    Today a professor of mine who teaches Electrical machines told us that a DC series motor should not be started without load. I wonder why is that so. Please provide a detailed explanation of this PF members. Thank you very much in advance.
  16. B

    Measuring motor resistance and speed of a geared DC motor

    Hi, I want to measure the motor resistance of a gear DC motor by experimentation and Ohm's Law. Should I measure the current without the gear head, with the gear head, stall current (with gear head) or stall current (without gear head)? I am trying to obtain values for Equation 4 in...
  17. B

    Model DC Motor: Torque, EMF, Resistance & Regulation

    Hello, I want to model a DC motor which I bought from a company. I only have the following information: torque constant [M.N.M./Amp], EMF constant [MV/RAD/SEC], Dynamic Resistance [OHMS] and Motor Regulation [RPM./M.N.M.]. The company does not provide the moment of inertia nor elect/mech...
  18. Arezriq_

    What are the best DC motors for moving heavy objects?

    what type of DC motors that can be use for moving a heavy object ?
  19. C

    Loading / Rapid de-loading of DC motor

    HiI have a device comprising a dc motor connected to a body and connected to the motor are four rotor arms. As the rotor arms are rotated they pass a point on the body that applies load to the motor then rapidly de loads the motor. So that every quarter turn the motor is loaded and then de...
  20. Z

    Need help with my project -- microcontroller for DC motor controller

    Hello, I'm a student currently doing my final year degree course in University College Sedaya International. I have given a project called as Microcontroller for DC motor control. The requirement of the project are :- 1). Type of Microcontroller = Microchip PIC16F876 2). DC motor 3). The...
  21. William123

    Choosing the Best DC Motor Brush Material: Tips and Recommendations

    Hello there Building DC motors has sort of become a hobby lately and I'm about to build the best version yet. However, I have a few questions when it comes to the brushes. I salvaged a couple of brushes from an old electric saw that my dad was throwing away but the resistance of those are much...
  22. T

    The relationship between Force, Voltage and Torque in DC motor

    how demonstrate the formula ? the relationship between Force and Voltage and Torque? how to prove that this formula? << e-mail address deleted by Mentor >>
  23. J

    Engineering How Does Armature Voltage Affect the Speed of a Separately Excited DC Motor?

    Homework Statement A 180V separately excited DC motor has an armature resistance of 1.2ohm. When the note runs at 1200rpm,t he armature current is 10A. 1) Assuming that motor torque is constant at all speeds,d determine the mechanical torque and power developed in the motor. 2)Find the speed of...
  24. R

    Calculating Armature Torque for 250V DC Motor

    Homework Statement A 250V shunt dc motor runs at 1000rpm while taking a current of 25 A. The motor has armature and field resistance as 0.2W and 250W respectively. Calculate (a) The speed when the load current is 50A. (b) Armature torque developed at both speeds. Homework Equations...
  25. E

    Engineering Electrical Machines DC Shunt Motor

    An 8.25 kW shunt DC motor is supplied with a terminal DC voltage of 300 V. The armature resistance of the motor Ra is 0.25 , and the field resistance Rf is 40 . The field winding consists of 1500 turns. An adjustable resistance Radj is connected in series to the field winding. Radj may be...
  26. W

    I want to replace an AC motor with a DC motor

    Ac motor is 1.12 amp 3000 rpm 60 Hz 1/30 Hp sealed ball bearing. I want to use a 12 V dc motor. Any help would be greatly appreciated. Thank you.
  27. B

    Electrical Choosing a DC motor for a DIY Centrifugal Blower

    I burned out my scavenged motor today and now I think I want to apply a little more thought to moving the project forward. I'm working on a centrifugal blower that can suck air through a charcoal filter so I can keep the air clean around my soldering area. I chose a tuna can for the housing...
  28. MacLaddy

    How can I safely vary the current to a variable torque DC motor for my project?

    I have recently learned that in order to vary torque output from a DC motor, I need to vary the input current. A project I am working on requires that I have a DC motor that will be backdriven while providing resistance to a lever. A max torque of about 10 lbft will be provided from the lever...
  29. J

    Help with Picking a DC motor for Electric Handcart

    Hello, So I am in the process of designing a stair climbing electric handcart/dolley capable of lifting around 500 lbs {Washer/dryer or Refridgerator} up stairs. The idea was to use an electric motor, preferably DC for HighTorque Low Speed and for my powering options. The idea was to use...
  30. C

    Using a DC Motor as a Generator

    So I'm working on a senior design project and was trying to use a DC motor to charge a battery. The point is to allow for quick use to charge a phone or a laptop in circumstances where you need a quick charge. We have lead-acid batteries connected in series and parallel to give us: 14,000mAh...
  31. Z

    Engineering DC Motor and armature current

    Homework Statement Hello I have a bit of a problem solving this A 20 kW, 500 V d.c. shunt wound motor draws a current of 45 A when running at full load with a speed of 600 rev min–1. On no load, the current drawn from the supply is 5 A. If the armature resistance is 0.3 Ω and the shunt field...
  32. D

    Which supercapacitor range is needed to run a 48V DC motor?

    I'm doing a project where I need to hand power for dc motor (12V or 24V) and charge a super capacitor, and then use it to drive another 48V dc motor. I want to know which Super capacitor will be suitable? Please give suggestions for Super capacitor specifications for both 12V and 24V that will...
  33. G

    What's the min power needed for a DC motor to move 5K lbs?

    I am making a some sort of an electric vehicle (cart) that will be used to move things around the two story warehouse. I am trying to figure out what would be the minimal power of an a DC motor, considering that the max speeds will be up to 10 MPH, while being able to push forward to the second...
  34. H

    DC Motor for Miniature Car

    Hello all, I'm building a miniature vehicle and plan on using a DC motor that supposedly spins at 12800 rpm (1340 rad/s) for the engine. However, I'm a little confused as to what the car's acceleration would be. The DC motor on its own would instantaneously have an angular velocity of 1340...
  35. marellasunny

    Alternatives to varistors as overload protection at DC motor

    Alternatives to varistors as overload protection at DC motor DC Motor here implies 12V linear actuator w/DC Motor that consumes 2.8A under loading condition. Pretty costly equipment. I'm using a L298N motor driver connected in parallel to run the linear actuator. The motor driver is run by a...
  36. S

    Makeshift DC Motor Radiating EMF

    My brother is a high school student tasked with making a DC motor. It is finished and works however I thought for the sake of learning and the additional cool factor (I'm relatively new to this field), I could make an optical RPM sensor which I could tack on. So I made this...
  37. cyril joel

    Connecting 12V DC Motor to Two 9V Batteries

    Hello i am abeginer i have to connect a 12v dc motor can i connect it to two 9v batteries in series meabs a total output of 18V.
  38. marellasunny

    Linear actuator limit switch replacement/repair

    Linear actuator spec.: 400mm stroke, 6000N, 2 limit switches, 5mm/sec, 12V DC supply, BIBUS IP65 casing. One of the limit switches of my LA (Linear Actuator) seems to have burned out. This happened because I accidentally plugged the LA leads into the AC mains socket (my LA is rated to run at...
  39. Narayanan KR

    A motor design to defy Lenz' law?

    1. The two rotors (purple, green) are electricaly isolated but mechanically fit to rotate along same axis 2. The motor action on the left side rotor will move the armature set, this will produce currents in right side rotor that will pass via a variable load. 3. do you see the magnetic fields...
  40. J

    Power Output Given Certain Torque

    Hi, I have a problem that I've been trying to figure out for a while but cannot seem to get on my own. I'm trying to figure out how much power will be generated in a motor given a certain amount of torque. The problem is, to find the amount of power output , I also need to know the rotational...
  41. alexandria

    Electric DC motor, commutator, carbon brushes, and magnets

    Homework Statement Homework Equations no equations required The Attempt at a Solution so here are my answers, i just want to know if they are correct. also, I am really confused about the function of the commutator in the DC motor, the answer i wrote for part b) was based on research off...
  42. Guidestone

    DC motor electrical and mechanical power relationship

    Hey guys, I know I still have a tread unanswered but I got a project in which I have to include some physical theory about the working of motors. I know P=V*I and also P=T*W where V is voltage, I is current, P is power, T is torque and W is angular speed. My question is, can I say V*I=T*W?. I...
  43. A

    Best design for a 300 watt permanent magnet brushed DC motor

    I have noticed there are a few designs for permanent magnet brushed DC motor, but I can't seem to find the benefits and downsides of either one. The first one (first attachment) uses three electromagnets placed on a triangular rotor. There are two arc permanent magnets on the outside. In this...
  44. T

    Engineering What are the reluctance values for this DC Motor?

    Homework Statement Homework EquationsThe Attempt at a Solution I know from a basic magnetic circuit that their will be an Rcore and an Rairgap but what about the rotor in the middle ?
  45. C

    Looking for the right DC motor

    Hello forum. I'm looking for a DC motor for a little project. I don't have a lot of experience with different types of motors, though I'm fairly confident I don't want a servo motor or a stepper motor. I have a disk of non-uniform weight distribution. I want to mount the disk vertically (motor...
  46. O

    How does a DC motor work without a commutator?

    How can this DC motor work without a commutator. Should it not turn no more than once and then stop because on one side the rotor is attracted to the magnet? An answer I can think of is that the rotor is repelled on one side and attracted on the other by the same force which neutralize each...
  47. H

    Small DC motor run by a super capacitor - Is it possible?

    I'm doing a project where I need to hand power one small, dc motor (1.5-12V) and charge a 1F 5.5V super capacitor, and then use it to drive another small 1.5-12V dc motor. Does anybody have any suggestions for motor specifications or circuit elements that will help me get the most efficiency...
  48. R

    Calculating the speed taking into account the weight of a person

    I need to buy a DC motor for an electric skateboard project. I need to calculate the speed at which it can travel with a person on top. I can calculate the speed at which the skateboard can go but is does not account for the weight of a person as that will surely decrease the speed. What formula...
  49. N

    Engineering Calculating Power Loss and Input for a Permanent Magnet DC Motor

    Homework Statement A permanent magnet DC motor has an armature resistance of 0.4 Ohms. When a voltage of 110 V is applied to the motor it reaches a steady-state speed of rotation of 126 rad/s and draws 39 A. (a) Find the power loss in the armature (b) the power input to the motor I really...
  50. K

    Expert Tips for Choosing the Perfect Motor - Maximize Your Design's Performance

    Hello, I am working on a design, and I am having trouble selecting a motor. I will be able to supply 1.2 A and 12VDC, and I need the motor to be able to move a load of 0.5 lbs at 500 rpm. So far, I tried calculating torque (based on F=ma and T=Fr, r=1.06 in in this case). Then I used HP=...
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