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. I_am_learning

    Is conventional commutator DC motor still in use?

    I think most of them are replaced by brushless types or Induction Motor with VFD (variable frequency drive). Is there some industries where they are still preferred today?
  2. T

    Brushless DC Motor torque calculations?

    Hi there guys and girls I am new to this forum , so please have mercy. I am searching for equations to calculate the torque of a 3 phase brushless dc motor. Any info or textbooks on this maybe? Thanks Tommie Prinsloo
  3. B

    Sizing a DC motor to move a weight and counterweight

    This might be a silly question for some but I was wondering how do I size a DC motor to move a weight and counter weight? Suggestions for a better design are also welcome. I want to build an enclosure with an automatic door (simple limit switches and an arduino to flip the motor on and off)...
  4. C

    DC Motor: Wooden vs Metal frame/shaft

    In DC motor or even in AC motor, if we use wooden frame and shaft, would it be advantageous than using Metal frame and shaft? Assume that would can with stand any temperature.
  5. B

    Brush DC Motor Science Project HELP

    So I have a Gr 11 Physics Science project. I need to build a Brushed DC motor. I already build an armature with coils. I have a copper commutator and copper are connected to it. Lastly, I placed electric tape on the wood body The problem is that I don't know how to make an effective Brush...
  6. D

    How do I calculate DC motor speed for a given load?

    A Wheel of a self balancing skateboard of radius 7 cm is rotating at 2600RPM with torque for motor is 1.76Nm,current is 10.4Amp and 24v and total load is 90kg (10kg for skateboard and 80kg for user). What is the speed of self balancing skateboard the in km/hr with load?
  7. 3

    Making a DC motor speed question

    I've made a simple DC motor like this image: http://farm4.static.flickr.com/3156/2864655414_234d5d3207.jpg I'm just confused why initially when i increase the number of loops (about 15) it spins faster.But after this limit the speed of the rotor is no longer as fast as it was before. Why...
  8. 3

    Make a DC Motor: Tips to Increase RPM to Over 5000

    Hi there Currently in my physics class my teacher has assigned us a project where we are to make a DC motor using these items: 2 thumbtacks 1 meter of 14 AWG copper wire 2 paperclips A block of wood 1 ceramic magnet 1 AA battery 2 connecting wires My plan is something like this...
  9. beyondlight

    Engineering Controlling DC Motor using DC-to-DC Converters

    Homework Statement We have a small car that is powered by a battery that feeds a DC-motor. The system consists of two DC-to-DC converters that controls the rotor and stator current. The DC-motor i separately magnetized. The purpoce of the DC-to-DC converters is to modulate the time the...
  10. O

    Finding the Right Fuse for 24V DC Motor Application

    I have an application where I am using a 24V DC motor to drive a ball screw. If someone isn't paying attention and they hit the mechanical stop on the ball screw, the current is going to spike to about 200 Amps. The normal running current is about 35 amps, and the max current is 60 amps...
  11. M

    Unclear properties of DC motor

    Hello everyone For a project I'm currently working on, I need a dc motor which can generate a torque of about 0.1-0.2 Nm (or more) with a rpm of about 120-200...
  12. W

    DC Motor Generator: Understanding Voltage and Current | FAQs

    Ok, I'm new to electronics and have some pretty simple questions that I can't seem to find answers to elsewhere. Let's say I have a DC motor that I want to use as a generator with the following specifications: 130 VDC 17 A 5950 RPM I know that in order to generate 130 Volts, that would...
  13. D

    Help Sizing a DC Motor for a 1958 Corvette

    I am new here and don't know if this is appropriate so let me know. I am not an engineer and no formal training other than a few Physics classes in college many years ago. I do however have a high mechanical aptitude and have always done some personalization of machines. Eg. I put a lawn mower...
  14. T

    Troubleshooting Brushed DC Motor Health: Insights from an Automotive Technician

    Hello, I am an automotive technician so I work with a lot of 12volt DC motors. First, it seems to me that bad connections or wires can cause excessive voltage drops to motors, but I don't understand what the difference is between a good cable and a bad cable. Or what qualifies a good...
  15. S

    DC motor and AC generator's output

    To increase a DC generator's turning effect, we increase the number of turns of the coil. How does this increase the turning effect? Will it concentrate the field lines or will the force acted on each coil be added to each other to increase the force on one armature? I think both happens because...
  16. S

    DC motor turning at constant speed eventually

    Hi, I have a question related to the DC motor that i hope you geniuses can help me with. By Fleming's Left hand rule, there is an induced forced (IF in diagram) at the downwards position at the armature AB. Thus, by Fleming's Right hand rule there is an induced current (IC in diagram) which...
  17. M

    Is there a delay of 1 or 2 seconds in generation of back emf in a dc motor

    Does the back emf in a dc motor start to appear after a slight delay(say 1 or 2 seconds) after starting up the motor? I have had this simple doubt for a long time.According to the "generator principle" both applied emf and back emf will always exist simultaneously.Also it would be in violation...
  18. S

    AC generator and DC motor problem

    Homework Statement For an AC generator, my teacher told us that when turning it, you will slowly manage to turn it at a constant speed only because of the induced current causing a force in the other direction to the turning motion. Why is this so? For a DC motor, my teacher told us that after...
  19. L

    DC Motor failed to run on load

    Hello, Im using DC motor to run the conveyor but suddenly the armature shows high current 130 A for 30 V power and the speed can't increase anymore. The motor power stated in the name plate is 93.8 KW, Armature voltage is 453 V and Armature ampere is 225 A. The motor can run free load after...
  20. F

    Creating large DC Motor for Funzies. Won't work.

    A picture I included shows how my motor is constructed. The basic science fair project looking engine. This engine is actually designed to do work, however, it will not turn over once DC is connected to it. The wire is close to 5/64 inch thick and the whole rotor is solidly soldered...
  21. N

    AC motor vs. DC motor efficiency

    I am currently using a 600HP DC motor for an extruder application and I am exploring the idea of switching to a 600HP AC motor. What kind of energy savings/efficiency can I expect if any?
  22. S

    How do i control the speed of a dc motor?

    I was thinking of using a 3 speed or dimmer switch to control the motor speed.
  23. H

    Need DC motor having high holding torque

    Hello Mates, I m making my project on Wireless robotic arm using microcontroller. I need DC Geared Motor with following specifications: 1) low RPM. 2) High Starting torque. 3) High Holding torque. Can any1 please help me in selecting motor ??
  24. M

    DC Motor Efficiency: Does It Change With Voltage?

    Hello, I would like to know if the motor efficiency is changing with respect to applied voltage or it doesn't change. What I do mean. The efficiency=(V*I)/(Torque*velocity) and the power losses= I^2*R. Can I say that mechanical power ( Torque*speed)=V*I-I^2*R If so, can I say that the...
  25. M

    Help with pulse dc motor calculations- torque, eff, hp

    Hello all, I have a few questions about calculating efficiency, torque and horsepower for a small pulse dc motor. The only parameters that I have are input voltage = 39Vdc, input current = 2A and rpm = 90,000 rpm. Are the above values obtainable with the given information? This is not a...
  26. S

    How do i choose the right ac or dc motor

    I'm building a wire strippers by cutting a hole in a piece of 2x4 which has a blade on the bottom of the hole. I want to use a motor to pull the wire threw by using a motor a gear and a strip of metal. The strip of metal clamps the wire down on the gear which is turned by the motor. I was...
  27. M

    Calculating torque within a DC MOTOR?

    The torque that is generated inside a magnetic motor is caused from the magnetic forces that is this formula: F = ILB F: Magnetic force(Not sure what the unit would be...) I: Current(A) L: Torque(N.m) B: Magnetic field.( Gauss or Tesla?) I just need some help in calculating the total magnetic...
  28. M

    How to control DC motor speed?

    Hi everyone, I have a 24V, 15A D.C motor, and need to control its RPM. I know RPM is directly proportional to voltage, and so the answer lies in a technique to vary the voltage across the motor. I have looked into potentiometers, variable resistors, and pulse-width-modulation, but since I...
  29. M

    Find DC Motor for Turntable with Built-In Brake Mechanism

    Hi all, I came across this forum and feel as though someone can point me in the right direction. I am looking for a 12v DC motor to power a turntable, I have a speed controller to slow the motor down. I need to know if there is a DC motor available to buy which can't be turned by hand, a...
  30. A

    DC motor rotor + stator : torque by attraction ?

    DC motor rotor + stator : torque by attraction ? [Solved] So on that image there's a very simple dc motor. Knowing that F = B*I, the force acting on the wire can be represented as on the image. Also the current passing through the rotor will create a magnetic field, represented by Brotor...
  31. M

    Need to choose DC motor with correct specs

    Hi everyone, As part of a project, I need to rotate a horizontal solid aluminium cylinder of approximately 15kg mass, 15cm radius and 8cm height such that its surface speed is a constant 160km/h. I need a D.C motor capable of achieving this. The acceleration of the wheel does not matter much...
  32. S

    Why is a DC Motor Self-Starting vs. an AC Motor?

    Can someone explain me why dc motor is self starting differ of ac who is not self starting motor?
  33. K

    Archived DC motor in series, finding the speed

    Homework Statement when running at its rated load, a 40kW series motor takes 74A and 550V. The rated speed is 750 rev/min. the armature and field resistances are 0.35 Ω and 0.15 Ω respectivly. when the load torque is doubled the rated value, the current is 110A. dertermin the moror speed and...
  34. K

    Seaching for DC motor to be used as a human lift

    I am building a human lift for a vehicle. I am looking a for DC motor able to life 900 ft-lbs with a brake and the shaft is splined. Sending me a link to a company that sells this type of motor would be great. Thank you, Kevin
  35. M

    Speed of a Cumulative Compound DC Motor

    I came across an equation for the Speed ω in Radians/seconds of a Cumulative Compound DC motor. ω= K(Vt-IA[RA+RF)/(\PhiP+\PhiS) How would we calculate K in this equation? Shouldn't the Terminal Voltage Vt be replaced by Armature Voltage Ea? I came across a lot of varying torque speed...
  36. O

    The back EMF of a DC motor spinning at full speed

    Homework Statement The resistance of the armature windings of a DC motor is 5Ω. The motor is connected to a 120V line. When the motor is spinning at full speed, it draws a current of 4A. The back EMF at full speed is: Homework Equations Pav=\frac{1}{2}I2peakR Pav=\frac{1}{2}εpeakIpeak...
  37. D

    Questions concerning about brushless dc motor

    questions concerning about the brushless dc motor in a brushless dc motor,does the power given by a battery move in and out throughout the electric current of the magnetic wire? I have the magnetic wires both parallel to each other and placed at the negative and positive terminal of the...
  38. T

    MATLAB How to simulate a Brushless dc motor drive in MATLAB/SIMULINK? thanks.

    I have uploaded the journals which related to the brushless dc motor. I encountered the problems as i don't know how to simulate the voltage source inverter of the Brushless dc motor system (the generation of inverter line to line voltages) and the hysteresis current block. i really need help...
  39. A

    DC motor mounted on a glider which slides linearly on a frictionless surface

    Hi guys,if i mount a dc motor on a glider that slides in 2 directions without friction, AND, instead of having it drive a mechanism, have a circular plate with an eccentrically drilled hole in it (not centre) mounted on the motor shaft though this hole, i should observe the glider sliding back...
  40. B

    Resistance of DC Motor Experiment

    Hey all, I have a small question that's been bugging me and I can't find an answer anywhere. How do you test the resistance of a DC motor? My main "practical" idea is to test it as you'd test any other piece of metal: connect a power supply, an ammeter and a dc motor in series, and connect a...
  41. M

    Direction of rotation, brushless or brushed DC motor

    I still don't understand why these types of motors tend to spin in one direction or another. In theory the direction of spin should be random since when the north pole of the rotor magnet is lined up with the north pole of the electromagnet in the stator the rotor could be repelled clockwise or...
  42. Z

    Solving DC Motor Issue with Rotor Inertia (J) Change

    Hi guys, I have built a simulation model for a permanent magnet DC motor, but I am having trouble accepting the results. dynamic equation states. machine accelerates as long as there is torque imbalance between elctrical and load torque, below. dw/dt = (1/J)*(Telectrical - Tload - Tfriction)...
  43. S

    Why is there an induced current in a dc motor?

    When I put a current into a dc motor, there will be a turning effect. But I thought as this happens, won't there the an induced current that flows in the opposite direction? Bt Fleming's Right hand rule, the current will flow in the other direction. So I'm quite confused about this...
  44. B

    Converting an electrical appliance with DC motor to AC watts

    Hi, I'm comparing two electrical appliances, one with a DC motor and the other with an AC motor. The AC appliance has 250 watts. The DC appliance has 0.6 amps and 120 volts, and its wattage is 72. Given these specs, I would like to know which appliance would have a more powerful motor? In...
  45. X

    Constructing a DC motor driver

    So in my SKIL course, (SKIL is the name of the lab courses (1 through 6) physics majors take. This course is about non-linear circuits) we need to develop some type of project that incorporates what we learn in the labs. The course deals with.. -Operation Amplifiers (Op Amp's) -Diodes -BJT...
  46. E

    Need help in controlling the speed of DC Motor ?

    Need help in controlling the speed of DC Motor ?? Can anyone of genius mind here tell me how to control the speed of dc motor in four quadrant operation automatically without using microcontroller or PLC ?? I Want to do a mini-project where i want to setup a speed from a keyboard input so...
  47. T

    DC motor armature winding question

    Hello, I am rewinding the armature for a burned up winch motor. This tutorial ( http://scootersupport.com/motorrewind.htm ) shows basically the exact same motor (but for scooters). The picture shows the armature. My question is, please help me to understand- each coil around the armature...
  48. P

    Engineering What are alternative techniques for starting a DC motor from rest?

    Having been asked to identify two methods of starting a DC motor from rest, I am struggling to get anything on the internet apart from Rheostats. Does anyone know of another technique that can be adopted for DC motor start-up? no equations required Knowing that the aramture...
  49. M

    Simple control circuit for a dc motor to power a conveyor for 5 seconds

    I am a hobbyist, and I am not too familiar on to how to run motors. Can someone help me design a simple circuit that drives a dc motor on pulley drive of a conveyor belt. I only need a steady speed, I am not changing speeds. The conveyor belt has to stay on for 5 seconds after a switch is turned...
  50. M

    Dc motor load increase as rpm increases?

    I have a dc motor geared to a diaphragm pump, and all hardware are unchanged. As i increase the supplied voltage, rpm increases, but so does the current (torque). I thought rpm increase would lead to higher back emf, and thus lowers the current. So would the only reason for my increased...
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