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# What is BACK EMF IN DC MOTOR?

In a motor using a rotating armature and, in the presence of a magnetic flux, ... the term "Back-EMF" often refers to using the voltage generated by a spinning motor to infer the speed of the motor's rotation. Efficiency
http://en.wikipedia.org/wiki/Counter-electromotive_force
Best Answer: a) Yes. I = V/R = 24/10 = 2.4A. This is because initially the motor is not turning and no back emf is being generated, so the system behaves like a simple ...
Wednesday, 02 August 2006 Permanent-magnet motors, the most common DC motors, generate a voltage when they rotate. This voltage, or "back-EMF" voltage, is directly proportional to the motor velocity.
Articles: Back-EMF Motion Control Feedback ... Introduction. Back-EMF refers to using the voltage generated by a spinning motor (EMF) to conclude the speed of the motor's rotation.
http://www.acroname.com/robotics/info/articles/back-emf/back-emf.html
When current is flowing through the armature conductor of dc motor, it starts rotating inside the magnetic field of stator pole. As the armature conductors move inside the magnetic field there will be an induced emf in the armature conductor.
DC Motor Model. CIRCUIT . DC_MOTOR_MODEL.CR Download the SPICE file. Although SPICE does not ... But, with 0V applied to the motor, all of the back emf now appears across RM and LM causing the current (and torque) to reverse!
http://www.ecircuitcenter.com/Circuits/dc_motor_model/DCmotor_model.htm
In dc motor, the armature conductors are revolving in the magnetic field and emf is induced in the armature conductors. The direction of the induced emf is in opposite ...
The Direct Current Motor In steady-state, an AC motor always rotates at the alternation frequency of its power ... In this case, the motor will spin up until its back-emf is slightly less than the external emf , so that very little current flows through the motor [according to Eq. ...
http://farside.ph.utexas.edu/teaching/302l/lectures/node93.html
Fig. (4.3) ZN/60 A) is large and hence the motor will draw less armature current and vice-versa. 4.4 Significance of Back E.M.F. The presence of back e.m.f. makes the d.c ...
To simplify things, a back emf controls current. This means it is responsible for the amount of electricity coming from the motor. Without a back emf, the motor
Once a motor is spinning so fast that the back-EMF is equal to the battery voltage (also called DC line voltage), it is impossible for the motor to be driven faster. References External links , Electric motor reference ...
http://en.wikipedia.org/wiki/Motor_constants
When a load is applied, the speed of the motor is reduced, which reduces the back emf and hence increases current in the motor. ... A simple AC/DC motor . A small electric motor. Much smaller electric motors are commonly used in a wide variety of daily situations.
http://lrrpublic.cli.det.nsw.edu.au/lrrSecure/Sites/Web/physics_explorer/physics/lo/induction_06/induction_06_01.htm
Electronics Forums > General Electronics Chat ... I got info in some web kept telling me that the back EMF of a simple motor is: Eemf ... No answers? Would my question be too ...
When a motor spins it generates a back emf. Let's see how this affects the current through the windings.
Physics > General Physics ... What causes the back emf in motors (brushless DC motors to be exact). First thing is ... Anybody? ... as for the generator aspect, yes. the motor ...
These components are the ideal motor, a back-EMF generator and parasitic resistance. ... Any DC motor can be turned into a DC generator simply by turning the shaft. When a motor turns due to applied voltage, it also generates back-EMF which is arranged to oppose the applied voltage.
http://www.girr.org/girr/tips/tips5/motor_tips.html
Brushless DC motors (BLDC) are used where there are limitations in the use of the brush-type DC motors. In this article we discuss how it is possible operate a DC motor with no brush arrangement and also explain the back EMF in a brushless DC motor (BLDC).
http://www.brighthubengineering.com/machine-design/75825-do-you-know-why-electric-motors-generate-reverse-electromotive-force/
Direct Back EMF Detection Method for Sensorless Brushless DC (BLDC) Motor Drives by Jianwen Shao Thesis submitted to the Faculty of the Virginia Polytechnic Institute and the State University
http://scholar.lib.vt.edu/theses/available/etd-09152003-171904/unrestricted/T.pdf
Back emf 'Universal' motors; Build a simple motor; AC motors (synchronous and stepper motors) Induction motors; Squirrel cage motors; Three phase induction motors; Linear motors; ... A simple DC motor has a coil of wire that can rotate in a magnetic field.
http://www.animations.physics.unsw.edu.au/jw/electricmotors.html
DC Motor: Index DC Circuits . HyperPhysics***** Electricity and Magnetism : R Nave: ... If the motor is not driving a load, then the generated back emf will almost balance the input voltage and very little current will flow in the coil of the motor.
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/motorac.html
Hi all, I have some questions regarding the back EMF problem on the DC motor. I have a 2 wire leads 160VDC motor that is connected to a electric
http://www.cnczone.com/forums/general_electronics_discussion/46522-back_emf_dc_motor.html
My question concerns Back EMF in DC brushed motors. I was told that the max velocity of a motor occurs when the Back EMF is equal to the voltage across the motor.
A dc motor is connected to a constant emf of 12.0 V. The resistance of its windings is 2.0 ohms. At normal operating speed, the motor delivers 6.0 W of mechanical power.
When current is flowing through the armature conductor of dc motor, it starts rotating inside the magnetic field of stator pole. As the armature conductors move inside the magnetic field there will be an induced emf in the armature conductor.
http://www.electrical4u.com/forums/topic/what-is-back-emf-in-dc-motor/
Electronics Forums > General Electronics Chat ... Hi, I am trying to understand what effect the induced EMF in a DC and AC motor has on ... The back EMF is only (nearly) equal ...
Is it valid to consider back-EMF in a DC motor equivalent to increased inductance? 6. How can I measure back-EMF to infer the speed of a DC motor? 7. Why should I worry about a motor causing my supply voltage to shoot up when the back-EMF can't exceed the supply voltage?-2.
http://electronics.stackexchange.com/questions/18447/what-is-back-emf-counter-electromotive-force
But also when the DC motor is turning, voltage appears on its pins, like a dynamo. ... shortening the 4ms during which the motor is not driven, but back-emf voltage is instead measured would allow us to measure more frequently, ...
http://robidouille.wordpress.com/2009/09/20/back-emf/
Hello friends, I had a doubt while studying inverters & converters in Power Electronics. In most of the circuits, (semiconverter, full-wave bridge
Hi all.. I've confused Now, we have a brush DC motor. We show that in a circuit as RLE load, am I right? R-> internal resistance, L -> inductance due to armature coils, E -> back emf due to rotation.
As the load on the motor increases, the back emf decreases as must be the case; the motor must be given energy to produce energy. To see why the back emf decreases under load is often complicated, ...
Does the back emf alternate back and forth completely or does it only vary sinousidally every half a period much like the emf provided in DC generators? ... the back-emf is negative as in a DC motor, and current is reduced. When the torque opposes the direction of rotation ...
DC motor behavior Obvious and non-obvious (but important to know) traits of DC motors. At a simplistic ... Because of back EMF, a spark is created at the commutator as a motor's brushes switch from contact to contact. Meanwhile, back ...
http://solarbotics.net/starting/200111_dcmotor/200111_dcmotor3.html
A prior art direct back EMF detection method synchronously sampled motor back EMF during PWM “off” time without the need to sense or re-construct the motor neutral in a sensorless brushless DC (BLDC) motor drive system. Since this direct back EMF sensing scheme requires a minimum PWM “off ...
http://www.freshpatents.com/Back-emf-detection-circuit-and-method-for-a-sensorless-brushless-dc--bldc--motor-dt20060713ptan20060152181.php
The back EMF produced by﻿ a motor, referenced here as the "y" voltage, is directly proportional to the rotational speed of the motor shaft. ... there is only emf. In a dc motor there is applied voltage and back voltage(emf) Also: ...
A DC motor on starting and stopping, the back emf is very large even it is in a very short period. Motor supply is from a rectified 220Vac@50Hz
http://www.electronicspoint.com/eliminate-dc-motor-back-emf-t27194.html
Best Answer: I guess you mean there are voltage spikes from the motor that cause interference. Or it could be voltage drop issues when the motor draws a high current. Without ...
Hi all, I want to know what is torque and back emf in DC motors. Please explain in brief.
Brushless DC motors (BLDC) are used where there are limitations in the use of the brush-type DC motors. In this article we discuss how it is possible operate a DC motor with no brush arrangement and also about the back EMF in a brushless DC motor (BLDC). Introduction A DC motor is a ...
http://electricalmotors.wordpress.com/2011/05/22/brushless-dc-motor-back-emf/
Working on motor control had always been my passion. For this project, I thought of working on something simpler in hardware. Hence it came out as a speed closed loop control of DC motor using back emf sensing.
http://www.techelex.com/2011/05/closed-loop-speed-control-of-dc-motor.html
AC Motors, electrical basics ... When the rotor increases its rpm, it will begin to generate a back voltage or counter-voltage.
http://www.industrial-electronics.com/AC-DC-motors/44_Counter-EMF.html
Dc motor back emf. Back emf of coil. Relay back emf diode. Elimination of back ... Emf detector. Emf protection. Emf health risk. Nearby Words. back clipping. back cloth. back country. back court. back cross' back crossed. back crosses. back crossing. back date. back dive. back door.
http://dictionary.reference.com/browse/back+emf
These components are the ideal motor, a back-EMF generator and parasitic resistance. ... Any DC motor can be turned into a DC generator simply by turning the shaft. When a motor turns due to applied voltage, it also generates back-EMF which is arranged to oppose the applied voltage.
http://www.trainweb.org/girr/tips/tips5/motor_tips.html
a) Yes. I = V/R = 24/10 = 2.4A. This is because initially the motor is not turning and no back emf is being generated, so the system behaves like a simple resistor (ignoring effects due to inductance of the coils).
http://www.qfak.com/education_reference/science_mathematics/?id=b967792
Best Answer: For a DC motor the back emf generated E in the armature is in opposition to the applied voltage V, So V = E + IaRa where Ia =armature current and Ra = armature ...
Parameterizing DC motor performance ... The back EMF constant is typically given in volts per unit of rotational speed (which in turn is generally expressed either in RPM or radians / second). If one takes the reciprocal of the back ...
http://solarbotics.net/starting/200111_dcmotor/200111_dcmotor4.html
At standstill, the motor speed is zero, therefore back emf is also zero. The armature current at starting is thus very large. Applying KVL in the field circuit of Figure 7: ... We know that the back emf for a separately excited DC motor:
http://vlab.ee.nus.edu.sg/~bmchen/courses/EG1108_DCmotors.pdf
I know that back-EMF can be considered as a voltage source in series with the motor which is proportional to speed. This is the common understanding, and I totally get it.
http://electronics.stackexchange.com/questions/53807/is-it-valid-to-consider-back-emf-in-a-dc-motor-equivalent-to-increased-inductanc
PPT ABOUT BACK EMF YOU CAN ALSO GET MORE PPT FROM MY MAIL radheys2011@gmail.com - A PowerPoint presentation
http://www.authorstream.com/Presentation/rsmeema-1687664-back-emf-electrical-dc-motor/
He originally worked for Thomas Edison, whose company was the main builder of direct current systems. They had a falling out over Tesla's advocacy of alternating currents as a source of power, and he left the company. ... A back emf appears in a motor after ...