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Reverse Running DC Motor = Generator

07/06/2011 7:59 PM

I am interested in the name and info of the DC motor which can run backwards and act as a generator.

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#1

Re: Reverse Running DC Motor = Generator

07/06/2011 8:18 PM

Pretty well any DC brush motor. (Bit more difficult with brushless).

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#6
In reply to #1

Re: Reverse Running DC Motor = Generator

07/07/2011 6:00 AM

Should've said "permanent magnet DC brush motor" .

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#7
In reply to #6

Re: Reverse Running DC Motor = Generator

07/07/2011 6:02 AM

(Shhhh, I don't think anyone noticed)

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#20
In reply to #6

Re: Reverse Running DC Motor = Generator

07/07/2011 10:49 PM

GA, any PM-DC motor runing any direction will act as a generator with direction related polarity, dont expect more power out than the moror rating... This is the simplest way.

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#2

Re: Reverse Running DC Motor = Generator

07/06/2011 8:29 PM

The name of mine is Lorentz Force.

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#3

Re: Reverse Running DC Motor = Generator

07/06/2011 8:54 PM

So, does it really have to run backwards to generate electricity?

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#14
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Re: Reverse Running DC Motor = Generator

07/07/2011 12:31 PM

Hmm? What is the polarity you want?

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#15
In reply to #3

Re: Reverse Running DC Motor = Generator

07/07/2011 12:38 PM

Yes but from rear end of shaft.

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#16
In reply to #3

Re: Reverse Running DC Motor = Generator

07/07/2011 12:54 PM

good point...I think driven and driving are more correct.

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#24
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Re: Reverse Running DC Motor = Generator

07/08/2011 3:00 AM

Depends how you wired the plug, very tricky issue.

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#4

Re: Reverse Running DC Motor = Generator

07/06/2011 10:34 PM

Hi all! New to this forum. Found this thread on Twitter, and decide to jump on...

Doesn't every DC motor generate (act like a generator) a counter force/voltage in the coil when running as a motor. No matter if rotation CW or CCW. The higher speed the higher counter force/voltage. That's why a DC motor draw less amps at higher rpm's (low load), and draw higher amps and makes higher torque at lower rpm's (high load).

A DC motor can be wired a few different ways....stator and rotor in series, in parallel (shunt?), and serie-parallel (compound?). And this gives DC motor different speed-torque characteristics

Also there is DC motors with permanent magnet stator or permanent magnet rotor (brush less DC motor)

It's 3+ decades since I studied this, so bare with me if I mixed up the terms...

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#17
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Re: Reverse Running DC Motor = Generator

07/07/2011 1:30 PM

Welcome to CR4!

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#18
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Re: Reverse Running DC Motor = Generator

07/07/2011 1:33 PM

This stuff is Tweeted?

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#25
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Re: Reverse Running DC Motor = Generator

07/08/2011 3:02 AM

Only the off topic

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#34
In reply to #4

Re: Reverse Running DC Motor = Generator

07/08/2011 11:11 PM

I think not Brushless.

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#5

Re: Reverse Running DC Motor = Generator

07/07/2011 3:16 AM

How much power do you want? If you are just trying to cahrge a mobile phone from wind power then a DC fan motor from a car will prob do the job.
Oh, and no, you don't have to run it backwards.
If you want more power then I dunno...
Del

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#8

Re: Reverse Running DC Motor = Generator

07/07/2011 8:50 AM

It may just be semantics, but a reverse running DC motor generator. A reverse running DC motor is simply spinning the opposite direction.

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#9
In reply to #8

Re: Reverse Running DC Motor = Generator

07/07/2011 8:55 AM

Yeah - the OP just got it a bit wrong. Obviously nothing to do with direction of rotation - he meant reversing the process of electrical to mechanical power conversion.

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#10

Re: Reverse Running DC Motor = Generator

07/07/2011 8:56 AM

Try these:

  • Portescap RG4
    • 1219
    • 16C1
    • 16M1
    • 1624
  • Airfix 1001
  • Tri-ang
    • XT60
    • X04
  • MW 005
  • ECM
    • type 1
    • type 2
    • type 3
  • plenty of Mashimas
  • plenty of Maxoms
  • etc., etc.

http://cgi.ebay.co.uk/Airfix-1001-5-pole-12v-dc-electric-motor-/110678531084

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#41
In reply to #10

Re: Reverse Running DC Motor = Generator

07/11/2011 6:18 AM

........also the Tenshodos.........

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#11

Re: Reverse Running DC Motor = Generator

07/07/2011 11:29 AM

2$ Investment on this can enable you to experiment at home, bypass electronic circuit board and you can get a sine-wave output to light an LED or to charge your cellphone when you are driving car,you can mount it on front bonnet of your car.

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#12

Re: Reverse Running DC Motor = Generator

07/07/2011 11:34 AM
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#19
In reply to #12

Re: Reverse Running DC Motor = Generator

07/07/2011 1:44 PM

thanks...this was what I tried to mention...

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#13

Re: Reverse Running DC Motor = Generator

07/07/2011 11:36 AM
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#21

Re: Reverse Running DC Motor = Generator

07/07/2011 11:27 PM

You guys all got it wrong.

This fellow wanted to run an electrical motor in REVERSE DIRECTION. Now, why do you all insists confusing him on bloody details he never asked for?!?

I oblige to stick to the question, exactly as asked. Yes, my friend, a motor in reverse is still a motor. But, if you intend to drive it [darn it, I have to catch myself, and not expand on assumed (you know, what that means, don't you) tangents of a question]. Now, if you mean to drive the motor weakly, it still is a motor. On the other hand, if you drive your motor quite vigorously, it may act as a generator.

I hope, and work for enlightenment! Or lightement, if that is not within reach.

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#26
In reply to #21

Re: Reverse Running DC Motor = Generator

07/08/2011 8:29 AM

1.The OP clearly states generator

2.Please explain your statement: " if you mean to drive the motor weakly, it still is a motor. On the other hand, if you drive your motor quite vigorously, it may act as a generator."

3.Often questions are not set quite clearly as the OP is clearly not an expert, answers need to be given to cover all interpretations and be understandable by the non initiated...

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#22

Re: Reverse Running DC Motor = Generator

07/08/2011 12:20 AM

You guys who don't understand the concept of back EMF in DC motors would do well to go back and study the subject before you add any more confusion to this topic. Sorry for being a PITA.......... Ed Weldon

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#23

Re: Reverse Running DC Motor = Generator

07/08/2011 2:12 AM

I don't think it's been mentioned that you can't have electronic commutation, it needs to have brushes.

Even some of the small DC muffin fans have electronic switching, so check before you buy.

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#27
In reply to #23

Re: Reverse Running DC Motor = Generator

07/08/2011 8:44 AM

This is a gross generalization, a permanent magnet rotor in a motor will generate electricity but will not have brushes. Electronic commutation motors can be used as generators if a proper electronic circuit is used, not simple but possible.

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#28

Re: Reverse Running DC Motor = Generator

07/08/2011 11:39 AM

Any DC motor (and most AC motors) can also act as a generator. Since the ideal characteristics for motor and generator are not the same, the best compromise has both series and shunt field coils, with the polarity of both field coils in the same direction when operating as a motor (cumulative compounding).

As several posters have stated every motor produces a back-voltage, also called counter-electromotive force (CEMF). If the generated voltage is greater than the applied voltage, the motor becomes a generator. This is usually accomplished by increasing the current through the shunt field coil. Raising the speed of motor shaft will also do it. The direction of rotation does not change, simply the direction of power flow.

Before electronic inverters were commonly available, motor-generators were used to provide backup power. An AC motor and a DC motor were coupled together on a common shaft. The DC end is connected to a battery set, and the AC end is in parallel with the normal AC supply for the critical load. When AC power is available, the speed of rotation is fast enough that the DC end generates a voltage greater than the battery, keeping it charged. When normal AC power is lost, the motor-generator slows down and the DC end begins to draw power from the battery, and the AC end becomes a generator at a slightly lower frequency.

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#33
In reply to #28

Re: Reverse Running DC Motor = Generator

07/08/2011 3:56 PM

Most AC motors cannot generate without using some very clever electronics as well.

DC motors, well most of them at least except brushless, will generate a small amount of power and also wear out the brushes at an alarming rate at the same time.....because the optimum point for the brushes for a motor, is not the optimum point for a generator, so you will get excessive sparking and heat, which may cause the commutator to overheat, loosen the glue and "explode"......

If the DC motor can have the brush position adjusted, its simple, move the brushes to the point of maximum voltage, minimum sparking......

I personally would use a proper alternator, like that from a car, which has the diodes to convert the AC to DC......replacing the rotor coil with a magnet can also be a good idea for some applications.

Just browse YouTube for thousands of videos showing just this......

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#29

Re: Reverse Running DC Motor = Generator

07/08/2011 12:40 PM

Would it not make more sense to just buy a generator? I would think that this option would be much more efficient, whatever your application.

What is your purpose, if I may be so bold as to ask?

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#30
In reply to #29

Re: Reverse Running DC Motor = Generator

07/08/2011 1:03 PM

Not if you are into an electric KER system, Kinetic Energy Recovery system, or a hybrid vehicle....

http://goo.gl/mBgG5

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#31
In reply to #30

Re: Reverse Running DC Motor = Generator

07/08/2011 1:56 PM

Or use a motor as an engine starter then reverse fields to act as a brake/dynamometer.

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#32
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Re: Reverse Running DC Motor = Generator

07/08/2011 3:43 PM

Ok, sorry for the assumption...I get the whole regenerative system backfeeding excess EMF and using an inverter to produce an AC signal, but itwould be helpful to understand KENN's application....

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#37
In reply to #32

Re: Reverse Running DC Motor = Generator

07/09/2011 12:00 AM

Yep, dead OPs are no fun... Retoric goes only so far, projects are more fun!

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#35

Re: Reverse Running DC Motor = Generator

07/08/2011 11:19 PM

The question is not clear.

I think that you mean " If motor is driven will it function as Generator"

If Ok then Yes.

If you drive the motor in reverse direction it will remain a motor but running in the reverse to the original designed direction.

If something else you mean then write a clearly understandable question to get a reply to your problem.

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#36

Re: Reverse Running DC Motor = Generator

07/08/2011 11:31 PM

Virtually all DC permanent magnet motors can be run in forward and reverse directions, and many run equally efficiently in either direction (with their brushes set to the neutral position, which is sub-optimal for either direction.) In fact, almost any motor of any type can be run in forward and reverse.

Every DC permanent magnet motor is operating as a generator while it is operating as a motor. This gives such motors their rpm-voltage relationship.

Any DC permanent magnet brushed motor can be used as a generator, and any such motor with movable brushes can be made to run equally efficiently as a motor or generator.

DC PM brushless motors can also be used to generate electricity, but doing so requires a rectifying bridge. Such machines are generally called permanent magnet alternators when used this way.

Any shunt-would DC motor is also a generator. (The old starter-generators used on lawn tractors are of this type.)

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#39
In reply to #36

Re: Reverse Running DC Motor = Generator

07/09/2011 5:24 AM

Most conventional starter motors are series not shunt wound......

I looked around on the web and I was unable to find an example of a shunt starter motor, though I would expect to find them where a vehicle (motor) needs to have a starter and generator all in one unit, but then they do two jobs, both not as well as a a dedicated start AND a dedicated generator/alternator.....

Its the heavy torque characteristics of a series wound motor that makes it such a good option as a starter motor.

Theory has it that an unloaded series motor will keep speeding up until it flies apart, though generally the drag of the (usually ball but not for vehicles though) bearings that will probably stop speed increase at some very high and dangerous speed.

DC motor driven fans on (older) DC ships are always series motors, mainly due to their quick start up, but need a constant mechanical load to stop over speeding, which the fan blades supply

There is a short comparison here:-

http://www.elec-toolbox.com/motorchar.htm

or here:-

http://www.dcmotorsinc.com/wound-series.php

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#40
In reply to #39

Re: Reverse Running DC Motor = Generator

07/09/2011 11:58 AM

Most conventional starter motors are series not shunt wound......
Of course.
The starter-generators used on old tractors (to which I referred) are not conventional starters. They are not really conventional shunt motors either, nor are they really a traditional compound motor. The generator field is shunt wound (connected across the armature output and ground, via the regulator.) The starter field is in series with the armature.
And you are right, neither function works particularly well.

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#38

Re: Reverse Running DC Motor = Generator

07/09/2011 4:23 AM

Motor or generator is mode of operation of electrical MACHINE. So if one gives supply to any DC machine, it would run as motor (converting electrical power into mechanical power) and if it is coupled to and prime mover and rotated (giving mechanical power) it will generate or convert mechanical power in to electrical power (off course, you need some residual magnetism to produce magnetic field or it should have permanent magnet).

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