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. Salvador

    Slip rings, commutator, dc motor

    If I'm not mistaking , all DC and also universal motors have a brushed commutator not a slip ring commutator because the rotor wires need to keep the same current direction as they rotate pass the same magnetic stator pole. so the only DC motor which could operate on slip rings is a homopolar...
  2. A

    Connecting an L293D H-Bridge to a DC Motor: Advice Needed

    Hello I was wondering if you could advise me on the following. I am undertaking a personal project at home (mainly mechanical in nature) whereby I require the L293D H-Bridge to connect to a 12 V DC motor. I'm using a PIC 16F877A microcontroller. This microcontroller has a 5V output. The...
  3. D

    Maximum voltage and current values for building a DC motor

    Hello, I am building a large DC motor for a Go-kart. I have a question: How would I know how much voltage and current (the maximum values I can use) I need to make the DC motor work and spin? I'm guessing the armature size and the winded wire's length depends on how much voltage and current...
  4. D

    How do I build a powerful DC motor for a go-kart?

    Hello, I would like to start building a simple DC motor Go-kart, but I would like to build my own DC motor for it. A simple one that can make the car move. I know how DC motors work and I understand the physics of it, but I'm not sure about some things: - Are all DC motors (large or small) the...
  5. E

    Which Simulation Software Best Optimizes a Lap Wound DC Motor?

    Im looking to simulate a lap wound permanent magnet brushed DC motor and am looking for advice on the best program. I've carried out some calcs in excel and wondering if I can simulate the motor in solidworks or Ansys to optimize placement and size of components in order to maximize efficiency,
  6. D

    Predicting DC generator response

    I am creating a scale model wind turbine using a DC motor as a generator and would like to predict the motor response analytically. Generally speaking, the flow will spin the rotor (as in the turbine's), which will spin the motor, and then there will be what I'm calling the motor response, and...
  7. A

    No Control Over DC Motor Speed After Bearing Change - Help Needed

    After bearing failure of 24V, 15A dc motor. We change the bearing of the dc motor. But after changing it the motor is running forward/ reverse but there is no control over the speed. Where is the problem? Is that in the techo or drive card? Any body please help. Helping in highly appreciated...
  8. T

    Understanding the Voltage Equation for a Separately Excited DC Motor

    Homework Statement Homework EquationsThe Attempt at a Solution For the textbook diagram of a separately excited dc motor, the voltage equation for the armature circuit is given as ##V_t=E_a + I_aR_a## But in the class notes, it says ##V_t = V_a## Firstly, I don't know if the ##V_a## refers to...
  9. T

    DC Motor: Solving for Load Speed w/ Torque Relation

    Homework Statement A machine, with an armature resistance of 0.16 ohms and K##\phi## is to drive a load that requires a torque that is proportional to its speed. One point on the mechanical torque-speed relation is 16 Nm at 400 r/min. If the armature terminal voltage is 50 V, at what...
  10. C

    Mechanism that only rotates when driven from one side

    I have a geared DC motor taken from a hand drill. When I manually turn the internal motor, the drill bit rotates. This can be done in both directions. However If I try and turn the drill bit it does not rotate. What is the mechanism called that achieves this? My friend says it is a sprag...
  11. B

    DC Motor & Drive: Find the Perfect Match for Your Needs

    Hi there, I've been looking through the web for hours but I cannot find a DC drive that can do everything I have in mind. After a few hours and being thoroughly confused. I was wondering if someone on this forum would be of any help. I'm trying to buy a 0.5 HP Permanent magnet DC motor to...
  12. M

    Car acceleration force required to size a DC motor torque

    I'm working on making a model car, and am trying to calculate the torque required to accelerate the car from a stop to 1.22m/s in 1 second, so I can pick out the right DC motor... The acceleration required is 1.22m/s/s (~ 4ft/s) The weight of the car is 0.85 kg The drive wheels diameters are...
  13. IamDev

    Specification of DC motor for my project work?

    Hello, I need to buy a DC motor for my project work. My project involves rotation of a cylindrical disk of 1 kg, inside water (approx. 2 cm below the water level) at different speed ranging between 100 rpm -200 rpm. For this purpose I need to buy a DC motor but I am not sure of what...
  14. R

    Speed regulation of a dc motor

    I am having confusion about the no load and full load speeds of a dc motor. What exactly does 'loading' stand for? How do we change the loading of a dc motor ?What is the relationship between loading and the speed of the motor? Which situations does no load and full load refer to?
  15. M

    Combining DC Generators for Increased Voltage Output

    Hi guys, I'm working on a school project and I don't know a lot about electricity, so here is my question. Let's say that I have two small 6V DC generators, and I need an output of 12V (I can not use a 12V DC generator because space is limited, the two 6V fit perfectly) is there a way to...
  16. Superposed_Cat

    Microcontroller, LED, DC motor problems

    Hey all, me and my friend are attempting to control a 5v dc motor and make a LED blink simultaneously using a H-Bridge Motor Driver 1A - SN754410 and ATMEGA328 micro-controller(16mhz, 8bit). The issue is is that when my H-Bridge activates the motor using input from the micro-controller then the...
  17. J

    Why does speed of DC motor increase when flux is reduced?

    I understand that from KVL e = v -IaRa e=k(flux)speed speed=(constant)*(V-IaRa)/flux But physically what causes the speed to increase? What force causes the rotor to accelerate? In fact physically, the rotor is moving because of field flux interacting with armature current's flux. So...
  18. M

    Engineering Using the Locked Rotor Test to find parameters of DC motor?

    Homework Statement A locked rotor test is performed on a permanent magnet DC machine with the following results: Terminal Voltage 5 V DC Input Current 10 A DC Locked rotor torque. 20 Nm a) Making suitable approximations deduce the effective rotor resistance in ohms? b) Making suitable...
  19. D

    Can You Set Up 4 DC Motors in Parallel with a Variable Resistor and LED Strip?

    Good day. I was wondering if anyone could help me with the following problem. As you can see in the diagram below, I want to set up a circuit with 4 DC Motors in parallel, each with a push button switch. And a variable resistor to control the speed manually. I would like a LED strip to be...
  20. A

    Adding a known load to a DC motor

    Hi everyone, I have implemented PI control of speed of a PMDC motor under no load condition. I now intend to implement the same with a load added to it. I want to compare the results with simulation as well. Is there any way of adding a known load to a DC motor. In my set up the dc motor is...
  21. N

    Sizing DC Motor for Large Robot (350 lb)

    I'm working on a senior design project. Currently I'm having some issues with sizing a motor for a large robot; everywhere I look I get different advice. I have a motor that I think will work but would appreciate some input. The specs are for our robot are as follows: mass = 350 lb = 158.8 kg...
  22. J

    Robotics DC Motor Help: Testing Motors for Project

    I'm currently trying to test the motors I bought for a robotics project to see if they'll work for our application and they seem to be much weaker than what should be expected based on the specs. During test, the battery is hooked directly to the motor and I'm measuring the current draw and the...
  23. Heros

    Uncovering the Mystery of Non-Linear Torque in Muscle-Powered Energy Conversion

    Hi, i didnt know where to put this question cos its kind of multitopic, here is why... I am working on a better way to take mechanical energy from muscles, i made a teste bench for pedalling in very different ways, including traditional(circular) pedalling, the thing is. I am measuring the power...
  24. B

    Engineering How Does Battery Configuration Affect DC Motor Speed?

    Homework Statement Hello, I am a 6th grade student trying to build a DC motor for the science fair. My hypothesis is that the dc motor will run faster if I place batteries in parallel versus batteries in a series. Is there an equation i can look at to explain what is happening? the mootr...
  25. S

    How to connect DC motor to Raspberry Pi?

    I have recently taken apart a few old DVD drives to see if there were any stepper motors available for a Raspberry Pi project I am currently working on. When I opened one of the older drives I found a motor which was unlike the others as it only seemed to have two wires going directly to the...
  26. S

    Can a 555 timer be used to control a brushless DC motor with the help of an IC?

    I have seen a link in this forum http://ww1.microchip.com/downloads/en/DeviceDoc/22263A.pdf that denotes an IC to control a brushless DC motor. How to connect it with a 555 timer? Can anyone help me with the entire circuit diagram? Thanks in advance.
  27. A

    Current control of DC motor using PI controller

    Hi everybody! I am trying to implement current control of a DC motor using a PI controller and was having a few questions. I am supplying 19V as input voltage (and capable of supplying current upto 2A) to the H- bridge and the controlling is done via a microcontroller using PWM. When I connect...
  28. H

    Variable low speed motor, how much can I vary it?

    I'm looking at getting a motor to drive a micrometer. It's on an interferometer mirror for the curious. I'll need around 1RPM or so, but I want to be able to vary the speed, because I'm pretty unsure about how fast I'll need it to go for my experiment to work. I'm thinking a range of like 1/4 to...
  29. Y

    How can I build a 12V DC motor controller for my fishing pole?

    I have attached a 12v DC electric drill moter to a fishing pole. I need a 12v dc motor controler or PWM that will allow me to cut the rpm's down from 550 rpm to about 20 to 100 rpm. less then 20 would work better for bottom fishing. I believe a PWM would work but I am not sure as to a...
  30. H

    DC Motor auto-reverse at low RPM

    Hi All, Much respect and admiration to the majority of you highly ordered beings. My question is a simple one I hope, how can I get a 24v DC motor to reverse ~half a rotation when forward RPM get low (0-10)? Thanks
  31. Y

    Super capacitor for running DC motor

    Hi, I am planning to run a DC motor using a super capacitor. The specification of the motor are: Voltage : 90V - 120 V DC Current : 15 A Duration : Should run for atleast 10 seconds. I have finalized this super capacitor from maxwell for the above operation...
  32. S

    Engineering How does current affect the speed of a DC motor

    Say I was run a homemade motor using a 9v battery, and then ran it again using two 9v batteries... would it go faster with the 18v?? Cheers
  33. S

    Why isn't my homemade DC motor working?

    I am building a two coil DC motor as a project. I have two neodymium magnets, an aluminium split ring, and alligator clips acting as brushes, connected to a 9v battery. For some reason it is not working and I cannot figure out why. Can anyone think of something I may be doing wrong. I can post...
  34. cavalierean

    Calculating Efficiency of a DC Motor: How Do I Determine In and Out Values?

    Hi I am trying to calculate the efficiency of my DC motor. I know that efficiency is: Power Out / Power In * 100 I have been told by my teacher that Power In is calculated by the following formula, Power In = Power * Time And Power Out is; Power Out = Mass * Gravity * Height...
  35. R

    Using resistor and DC motor acting as generator as a brake

    how would you calculate the resistance required for a resistor which is in series with a generator (DC motor in reverse) to achieve a certain torque from the generator? Eg, there's a torque of 30kN acting on a 100kW generator while it moves at 50RPM. The is the same mechanism as electric...
  36. G

    Designing DC motor with 8051 and transisors

    I want to design a bidirectional DC motor , so use four transistors in the H bridge circuit. I can understand the first circuit, but for the second, I can't understand why input signal , eg: A, is connected to the same side of transistors? What is the differences, which one I should...
  37. C

    How much power can a DC motor generate using water power?

    I have a 1.5 hp dc motor that I am going to use water power to turn . How much power can I expect from this . It is just a summer fun project .
  38. 9

    Cheapest Way To Reverse/Vary Speed of DC Motor

    Hi, I'm new here and had a question relating to my senior design project in mechanical engineering. My project ends up involving a small DC electric motor, which needs to be able to be reversed and it would be nice to be able to have some speed variability. I'm aware of speed controllers and I...
  39. jedishrfu

    Finding the Perfect DC Motor for Your Small Robotic Platform

    I'm looking for a DC Motor to power a small 50lb robotic platform with maximum speed of 10mi/hr. What should I be looking for? I've made some basic assumptions of 8" or 12" diameter wheels and so the rpm rating should 420 rpm and 300rpm respectively to attain 10mph. I plan to use at least two...
  40. G

    DC motor. Calculate the current

    Homework Statement The coil of a DC motor has a resistance of 2.0 ohms. The motor is runned by a battery of 12 V and an internal resistance of 0.5 ohms. a) Calculate the current at the moment the motor is started b) Calculate the current when the motor is running at 600 RPM , when there is...
  41. R

    Very silly question regarding DC motor

    If in the DC motor specs doc says that it can handle + - 16 Volts maximum and 3A of peak current but the nominal voltage is 6 V and the continuous current is 1A... it means that it is safe if you feed it with 3A during the time of start up? Supposedly it is only meant to be at the start...
  42. O

    DC Motor Field Current Speed Control

    I have a Geared DC Motor rated 12V, 0.6A, 180RPM, 3kg.cm, 66% Efficiency. I measured the impedance of the disconnected motor at 45 Ohm. I want to use it with a with a simple 12V 1A DC Power Supply in a Field Current Control Circuit to be able to dial in variable speeds. Will the circuit in...
  43. A

    Engineering Solving DC Motor Problem on Physics Forum

    People of physics forum i have come here to ask for help. i am trying to model a armature controlled dc motor with no load but and opposite force in the form of frictional damping the expression i have raised and am assuming it to be right is ωout/Vin = k/(L(s)+R)(I(s)+C)+ kt.k...
  44. Z

    Running DC motor at higher than rated speeds

    Hi, I had this power electronics lab experiment where we control the speed of a separately excited dc motor using thyristors. The dc motor is rated at 1500 RPM but we do get readings where the speed is above 2500 RPM. How is that possible? Thanks
  45. T

    How can I calculate the efficiency of a DC motor for different torque values?

    Hi, I'm attempting to make a model of a DC motor capable of calculating the efficiency of the motor for different values for torque. I have managed to make a code to generate the torque-speed-power plots for given inputs, however I have been unable to figure out how to calculate the...
  46. perplexabot

    Understanding DC Motor Modeling: Exploring the Role of Inductors and Back EMF

    Hello. Just started learning about how to model a DC motor. A simple model consists of the input Voltage in series with an inductor, a resistor and a back emf. I have two questions. Why have both the inductor and the back emf (voltage source)? If you know that at a voltage V and a load L1...
  47. M

    How Does Switch Frequency Affect DC Motor Performance?

    I've been looking around for formulas on how to calculate different aspects of DC motors and buck converters such as average current. The reason is that I'm about to pick switch frequency for a motor, and don't know what characterics I can expect if I alter the switch frequency. Papers and...
  48. P

    Is it okay to increase DC motor RPM by using higher voltage

    Hello guys I'm looking for a motor for my arrow saw project. I would like to use it to cut carbon arrows. Found one motor in the shop that is pretty small and will work perfectly with my jig. But it's rpm's are only 1650 and I need at least 8000 RPM. Is it possible to increase the motor RPM's...
  49. J

    How does this kind of DC motor work?

    Homework Statement I used a similar motor to this one in a prac, and then realized that the arms either side of the coils were not magnetised. I was wondering where the magnetic field comes from, and without any special equipment is it possible to calculate it? Homework Equations t=bain
  50. jegues

    H-Bridge Control of DC Motor: Battery Bank Voltage vs Motor Ratings

    If we assume we are using an H-Bridge to control the average voltage across a PMDC motor, is it still necessary that we place a buck converter between the battery bank and the H-Bridge in order to step down the voltage supplying the H-Bridge? I've attached a schematic of what I'm reffering...
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