Help Trying to Use D.C. Motor as Generator

[Techmann]

I have a D.C. motor that spins just fine when I apply 12V to it. The
motor has a 1/4" shaft and I would like to use it as a generator.
When I hook up a DC voltmeter to the leads and spin the shaft in the
same direction with my electric drill (around 1000 RPM) the most I
see out of the motor is only .24 volts. I am puzzled why I am not
seeing close to 12V output on this motor. Can only certain kinds of
DC motors be used as generators? Is it caused by the way the coils
are wired up internally and is there a way to test or change this so
that it can be made into a generator? Thank you.

T.C.

 

[Jasen Betts]

On 2008-12-04, Techmann <Inthemedia@yahoo.com> wrote:

I have a D.C. motor that spins just fine when I apply 12V to it. The
motor has a 1/4" shaft and I would like to use it as a generator.

When I hook up a DC voltmeter to the leads and spin the shaft in the
same direction with my electric drill (around 1000 RPM) the most I
see out of the motor is only .24 volts. I am puzzled why I am not
seeing close to 12V output on this motor. Can only certain kinds of
DC motors be used as generators? Is it caused by the way the coils
are wired up internally and is there a way to test or change this so
that it can be made into a generator? Thank you.

the easiest kind of DC motor to use as a genetator is one with
both brushes and permanent magnets, other kinds can be used
but will probably need to be modified.

 

[Clint Sharp]

In message <gh82i1$l3n$1@reversiblemaps.ath.cx>, Jasen Betts
<jasen@xnet.co.nz> writes

the easiest kind of DC motor to use as a genetator is one with
both brushes and permanent magnets, other kinds can be used
but will probably need to be modified.
All kinds of DC motor when used as a generator will need the output

rectifying or measuring with an AC voltmeter.
--
Clint Sharp

 

[default]

On Wed, 3 Dec 2008 23:06:20 -0800 (PST), Techmann
<Inthemedia@yahoo.com> wrote:

I have a D.C. motor that spins just fine when I apply 12V to it. The
motor has a 1/4" shaft and I would like to use it as a generator.
When I hook up a DC voltmeter to the leads and spin the shaft in the
same direction with my electric drill (around 1000 RPM) the most I
see out of the motor is only .24 volts. I am puzzled why I am not
seeing close to 12V output on this motor. Can only certain kinds of
DC motors be used as generators? Is it caused by the way the coils
are wired up internally and is there a way to test or change this so
that it can be made into a generator? Thank you.

T.C.

Yup only certain kinds. Some DC motors and all universal motors,
AC/DC (like your drill, vacuum cleaner, blender etc..) have field
windings to create a magnetic field. Some DC (only) motors use
permanent magnets to create the field - they make good generators
without modification. Some stepper motors make pretty good (if a
little small) AC generators.

A motor with a wound field can be made to work as a generator by
either exciting the field portion with a battery, or putting the field
in parallel with the armature so it is supplied by its own voltage.
(otherwise known as a parallel wound motor).

With that type of motor, used as a generator, the iron in the field
has to retain a little residual magnetism to start it producing power,
and it sometimes helps if it is not under an electrical load until it
starts producing current. A small permanent magnet can also be put on
part of the field to insure it starts (if the iron doesn't retain
enough magnetism - determined by the type of iron)
--


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[Tim Wescott]

On Thu, 04 Dec 2008 17:02:39 +0000, Clint Sharp wrote:

In message <gh82i1$l3n$1@reversiblemaps.ath.cx>, Jasen Betts
jasen@xnet.co.nz> writes
the easiest kind of DC motor to use as a genetator is one with both
brushes and permanent magnets, other kinds can be used but will
probably need to be modified.
All kinds of DC motor when used as a generator will need the output
rectifying or measuring with an AC voltmeter.

Absolutely totally wrong.

Go check your science.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

 

[Tim Wescott]

On Wed, 03 Dec 2008 23:06:20 -0800, Techmann wrote:

I have a D.C. motor that spins just fine when I apply 12V to it. The
motor has a 1/4" shaft and I would like to use it as a generator. When I
hook up a DC voltmeter to the leads and spin the shaft in the same
direction with my electric drill (around 1000 RPM) the most I see out
of the motor is only .24 volts. I am puzzled why I am not seeing close
to 12V output on this motor. Can only certain kinds of DC motors be
used as generators? Is it caused by the way the coils are wired up
internally and is there a way to test or change this so that it can be
made into a generator? Thank you.

T.C.

It's probably a wound-field motor, instead of a permanent magnet motor.
A wound-field machine will work just dandy as a generator, but you have
to supply field current.

If it goes the same direction no matter what direction you connect the
power then it's a wound-field motor. If that's the case, then you want
to find out how to excite the field separately. If it's a shunt field
then this will be easy, if it's a series field this will be difficult, or
at least oddball.

Does this motor have a nameplate?

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

 

[John Larkin]

On Thu, 4 Dec 2008 17:02:39 +0000, Clint Sharp
<clint@clintsmc.demon.co.uk> wrote:

In message <gh82i1$l3n$1@reversiblemaps.ath.cx>, Jasen Betts
jasen@xnet.co.nz> writes
the easiest kind of DC motor to use as a genetator is one with
both brushes and permanent magnets, other kinds can be used
but will probably need to be modified.

All kinds of DC motor when used as a generator will need the output
rectifying or measuring with an AC voltmeter.

No.

John

 

[Techmann]

On Dec 4, 8:12 pm, Tim Wescott <t...@seemywebsite.com> wrote:

On Wed, 03 Dec 2008 23:06:20 -0800, Techmann wrote:
I have a D.C. motor that spins just fine when I apply 12V to it.  The
motor has a 1/4" shaft and I would like to use it as a generator. When I
hook up a DC voltmeter to the leads and spin the shaft in the same
direction with my electric drill  (around 1000 RPM) the most I see out
of the motor is only .24 volts.  I am puzzled why I am not seeing close
to 12V output on this motor.  Can only certain kinds of DC motors be
used as generators?  Is it caused by the way the coils are wired up
internally and is there a way to test or change this so that it can be
made into a generator?  Thank you.

T.C.

It's probably a wound-field motor, instead of a permanent magnet motor.  
A wound-field machine will work just dandy as a generator, but you have
to supply field current.

If it goes the same direction no matter what direction you connect the
power then it's a wound-field motor.  If that's the case, then you want
to find out how to excite the field separately.  If it's a shunt field
then this will be easy, if it's a series field this will be difficult, or
at least oddball.

Does this motor have a nameplate?

--
Tim Wescott
Control systems and communications consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html

The nameplate says AiResearch Mfg Co. of Arizona, Inc. Motor -
Aircraft Direct Current with Thermal Protection 24V System
Type BDIB
Dwg. No. 25226
HP 1/8
RPM 7500
AMPS 9.0

It measures about 4-1/2" long by 2-1/4" in diameter, has a 7-splined
1/4" shaft and appears to be a high-quality motor.

It has 2 wires coming out (red & green) plus the case ground. When I
hook up battery (-) to the case and (+) to the red wire it turns CCW
(as looking at the shaft). If I reverse the battery leads it still
turns CCW. When I connect (+) to the green wire it turns CW. If I
reverse the battery leads to the green wire and case ground it still
turns CW. Between either red or green and the case there is 3.8 ohms
resistance and between the red and green wires there is 1 ohm
resistance. I am guessing that if was running as a generator that the
red wire would be positive voltage relative to ground while the green
wire would be producing a negative voltage relative to ground.

As you mentioned, since it turns the same direction no matter which
way the polarity is it must be a wound-field. Now how would I
determine whether it's a series or shunt wound? Another person wrote
that it's also possible to put the field
in parallel with the armature so it is supplied by its own voltage
(otherwise known as a parallel wound motor).

"With that type of motor, used as a generator, the iron in the field
has to retain a little residual magnetism to start it producing power,
and it sometimes helps if it is not under an electrical load until it
starts producing current. A small permanent magnet can also be put on
part of the field to insure it starts (if the iron doesn't retain
enough magnetism - determined by the type of iron)"

This sounds neat since I wouldn't have to use an external battery
source to excite the field but where is the best place to locate the
magnet and how big/strong would it have to be?

Thank you,

T.C.

 

[default]

On Thu, 4 Dec 2008 22:13:08 -0800 (PST), Techmann
<Inthemedia@yahoo.com> wrote:

On Dec 4, 8:12 pm, Tim Wescott <t...@seemywebsite.com> wrote:
On Wed, 03 Dec 2008 23:06:20 -0800, Techmann wrote:
I have a D.C. motor that spins just fine when I apply 12V to it.  The
motor has a 1/4" shaft and I would like to use it as a generator. When I
hook up a DC voltmeter to the leads and spin the shaft in the same
direction with my electric drill  (around 1000 RPM) the most I see out
of the motor is only .24 volts.  I am puzzled why I am not seeing close
to 12V output on this motor.  Can only certain kinds of DC motors be
used as generators?  Is it caused by the way the coils are wired up
internally and is there a way to test or change this so that it can be
made into a generator?  Thank you.

T.C.

It's probably a wound-field motor, instead of a permanent magnet motor.  
A wound-field machine will work just dandy as a generator, but you have
to supply field current.

If it goes the same direction no matter what direction you connect the
power then it's a wound-field motor.  If that's the case, then you want
to find out how to excite the field separately.  If it's a shunt field
then this will be easy, if it's a series field this will be difficult, or
at least oddball.

Does this motor have a nameplate?

--
Tim Wescott
Control systems and communications consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html

The nameplate says AiResearch Mfg Co. of Arizona, Inc. Motor -
Aircraft Direct Current with Thermal Protection 24V System
Type BDIB
Dwg. No. 25226
HP 1/8
RPM 7500
AMPS 9.0

It measures about 4-1/2" long by 2-1/4" in diameter, has a 7-splined
1/4" shaft and appears to be a high-quality motor.

It has 2 wires coming out (red & green) plus the case ground. When I
hook up battery (-) to the case and (+) to the red wire it turns CCW
(as looking at the shaft). If I reverse the battery leads it still
turns CCW. When I connect (+) to the green wire it turns CW. If I
reverse the battery leads to the green wire and case ground it still
turns CW. Between either red or green and the case there is 3.8 ohms
resistance and between the red and green wires there is 1 ohm
resistance. I am guessing that if was running as a generator that the
red wire would be positive voltage relative to ground while the green
wire would be producing a negative voltage relative to ground.

As you mentioned, since it turns the same direction no matter which
way the polarity is it must be a wound-field. Now how would I
determine whether it's a series or shunt wound? Another person wrote
that it's also possible to put the field
in parallel with the armature so it is supplied by its own voltage
(otherwise known as a parallel wound motor).

"With that type of motor, used as a generator, the iron in the field
has to retain a little residual magnetism to start it producing power,
and it sometimes helps if it is not under an electrical load until it
starts producing current. A small permanent magnet can also be put on
part of the field to insure it starts (if the iron doesn't retain
enough magnetism - determined by the type of iron)"

This sounds neat since I wouldn't have to use an external battery
source to excite the field but where is the best place to locate the
magnet and how big/strong would it have to be?

Thank you,

T.C.

You're going to have to pop the end plate off at the very least to get

at the connections. Most of the wound motors I've encountered have
been series wound.

The brushes are spring loaded and if you have access, take them out
before pulling the brush end off.

The choices are series, parallel, and compound (both - two field
windings on the poles). A little searching on the I-net will tell you
about them. Since you have a lead to reverse the motor it may have
two field windings (center tapped) and it is still a series wound -
not compound (compound: one field winding in series and one winding
across the armature)

As for locating the magnet . . . if it uses solid pole pieces or
laminated ones, just shave a little metal off a pole piece and epoxy
a (large surface, thin, rare earth) magnet in.

The gap between the armature and field should be small - it improves
efficiency up to a point, so don't grind away any more metal than you
have to.

But get it wound in parallel and see if it works - you may not need
any magnet.
--


----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.pronews.com The #1 Newsgroup Service in the World! >100,000 Newsgroups
---= - Total Privacy via Encryption =---

 

[Tim Wescott]

On Thu, 04 Dec 2008 22:13:08 -0800, Techmann wrote:

On Dec 4, 8:12 pm, Tim Wescott <t...@seemywebsite.com> wrote:
On Wed, 03 Dec 2008 23:06:20 -0800, Techmann wrote:
I have a D.C. motor that spins just fine when I apply 12V to it.  The
motor has a 1/4" shaft and I would like to use it as a generator.
When I hook up a DC voltmeter to the leads and spin the shaft in the
same direction with my electric drill  (around 1000 RPM) the most I
see out of the motor is only .24 volts.  I am puzzled why I am not
seeing close to 12V output on this motor.  Can only certain kinds of
DC motors be used as generators?  Is it caused by the way the coils
are wired up internally and is there a way to test or change this so
that it can be made into a generator?  Thank you.

T.C.

It's probably a wound-field motor, instead of a permanent magnet motor.
A wound-field machine will work just dandy as a generator, but you have
to supply field current.

If it goes the same direction no matter what direction you connect the
power then it's a wound-field motor.  If that's the case, then you want
to find out how to excite the field separately.  If it's a shunt field
then this will be easy, if it's a series field this will be difficult,
or at least oddball.

Does this motor have a nameplate?

--
Tim Wescott
Control systems and communications
consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html

The nameplate says AiResearch Mfg Co. of Arizona, Inc. Motor - Aircraft
Direct Current with Thermal Protection 24V System Type BDIB
Dwg. No. 25226
HP 1/8
RPM 7500
AMPS 9.0

It measures about 4-1/2" long by 2-1/4" in diameter, has a 7-splined
1/4" shaft and appears to be a high-quality motor.

It has 2 wires coming out (red & green) plus the case ground. When I
hook up battery (-) to the case and (+) to the red wire it turns CCW (as
looking at the shaft). If I reverse the battery leads it still turns
CCW. When I connect (+) to the green wire it turns CW. If I reverse
the battery leads to the green wire and case ground it still turns CW.
Between either red or green and the case there is 3.8 ohms resistance
and between the red and green wires there is 1 ohm resistance. I am
guessing that if was running as a generator that the red wire would be
positive voltage relative to ground while the green wire would be
producing a negative voltage relative to ground.

As you mentioned, since it turns the same direction no matter which way
the polarity is it must be a wound-field. Now how would I determine
whether it's a series or shunt wound? Another person wrote that it's
also possible to put the field in parallel with the armature so it is
supplied by its own voltage (otherwise known as a parallel wound motor).

"With that type of motor, used as a generator, the iron in the field has
to retain a little residual magnetism to start it producing power, and
it sometimes helps if it is not under an electrical load until it starts
producing current. A small permanent magnet can also be put on part of
the field to insure it starts (if the iron doesn't retain enough
magnetism - determined by the type of iron)"

This sounds neat since I wouldn't have to use an external battery source
to excite the field but where is the best place to locate the magnet and
how big/strong would it have to be?

Thank you,

T.C.

Look up that data plate on the internet and see if you can find useful
information.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

 

[Techmann]

On Dec 5, 10:50 am, default <defa...@defaulter.net> wrote:

On Thu, 4 Dec 2008 22:13:08 -0800 (PST), Techmann





Intheme...@yahoo.com> wrote:
On Dec 4, 8:12 pm, Tim Wescott <t...@seemywebsite.com> wrote:
On Wed, 03 Dec 2008 23:06:20 -0800, Techmann wrote:
I have a D.C. motor that spins just fine when I apply 12V to it.  The
motor has a 1/4" shaft and I would like to use it as a generator. When I
hook up a DC voltmeter to the leads and spin the shaft in the same
direction with my electric drill  (around 1000 RPM) the most I see out
of the motor is only .24 volts.  I am puzzled why I am not seeing close
to 12V output on this motor.  Can only certain kinds of DC motors be
used as generators?  Is it caused by the way the coils are wired up
internally and is there a way to test or change this so that it can be
made into a generator?  Thank you.

T.C.

It's probably a wound-field motor, instead of a permanent magnet motor..  
A wound-field machine will work just dandy as a generator, but you have
to supply field current.

If it goes the same direction no matter what direction you connect the
power then it's a wound-field motor.  If that's the case, then you want
to find out how to excite the field separately.  If it's a shunt field
then this will be easy, if it's a series field this will be difficult, or
at least oddball.

Does this motor have a nameplate?

--
Tim Wescott
Control systems and communications consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html

The nameplate says AiResearch Mfg Co. of Arizona, Inc.  Motor -
Aircraft Direct Current with Thermal Protection 24V System
Type BDIB
Dwg. No. 25226
HP 1/8
RPM 7500
AMPS 9.0

It measures about 4-1/2" long by 2-1/4" in diameter, has a 7-splined
1/4" shaft and appears to be a high-quality motor.

It has 2 wires coming out (red & green) plus the case ground.  When I
hook up battery (-) to the case and (+) to the red wire it turns CCW
(as looking at the shaft).  If I reverse the battery leads it still
turns CCW.  When I connect (+) to the green wire it turns CW.  If I
reverse the battery leads to the green wire and case ground it still
turns CW.  Between either red or green and the case there is 3.8 ohms
resistance and between the red and green wires there is 1 ohm
resistance.  I am guessing that if was running as a generator that the
red wire would be positive voltage relative to ground while the green
wire would be producing a negative voltage relative to ground.

As you mentioned, since it turns the same direction no matter which
way the polarity is it must be a wound-field. Now how would I
determine whether it's a series or shunt wound?  Another person wrote
that it's also possible to put the field
in parallel with the armature so it is supplied by its own voltage
(otherwise known as a parallel wound motor).

"With that type of motor, used as a generator, the iron in the field
has to retain a little residual magnetism to start it producing power,
and it sometimes helps if it is not under an electrical load until it
starts producing current.  A small permanent magnet can also be put on
part of the field to insure it starts (if the iron doesn't retain
enough magnetism - determined by the type of iron)"

This sounds neat since I wouldn't have to use an external battery
source to excite the field but where is the best place to locate the
magnet and how big/strong would it have to be?

Thank you,

T.C.

You're going to have to pop the end plate off at the very least to get
at the connections.  Most of the wound motors I've encountered have
been series wound.

The brushes are spring loaded and if you have access, take them out
before pulling the brush end off.

The choices are series, parallel, and compound (both - two field
windings on the poles).  A little searching on the I-net will tell you
about them.  Since you have a lead to reverse the motor it may have
two field windings (center tapped) and it is still a series wound -
not compound (compound: one field winding in series and one winding
across the armature)

As for locating the magnet . . . if it uses solid pole pieces or
laminated ones,  just shave a little metal off a pole piece and epoxy
a (large surface, thin, rare earth) magnet in.  

The gap between the armature and field should be small - it improves
efficiency up to a point, so don't grind away any more metal than you
have to.  

But get it wound in parallel and see if it works - you may not need
any magnet.
--

----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==----http://www.pronews.comThe #1 Newsgroup Service in the World! >100,000 Newsgroups
---= - Total Privacy via Encryption =---- Hide quoted text -

- Show quoted text -

My understanding is the field coil on a shunt-wound motor typically
has a resistance of several hundred ohms vs. the field coil on a
series-wound motor which is only a few ohms. For connecting the field
coil in parallel with the armature coil as you described, which type
of field coil would work best?

If I wanted to use a battery to supply voltage just to the field
winding and not connect it to the armature, it would seem that a shunt-
wound motor would be the much better choice since the coil has a
natural high reistance and thus it would require much less current
from the battery. Is my thinking correct here?

Finally, if I wanted a regulated 12 volt output, having a separate
field winding would be desirable since I could vary the voltage across
the field coil to maintain a constant voltage output. As a side
topic, I have a Chrysler regulator from an old Dodge Van which has
just 2 pins on a rubber connector plus case ground. I checked the van
schematic and the pins connect directly across the field coil. What I
don't understand is how does the regulator know the output voltage of
the alternator if it doesn't have a sense lead?

Thanks again

T.C.

 

[default]

On Fri, 5 Dec 2008 12:16:52 -0800 (PST), Techmann
<Inthemedia@yahoo.com> wrote:

On Dec 5, 10:50 am, default <defa...@defaulter.net> wrote:
On Thu, 4 Dec 2008 22:13:08 -0800 (PST), Techmann





Intheme...@yahoo.com> wrote:
On Dec 4, 8:12 pm, Tim Wescott <t...@seemywebsite.com> wrote:
On Wed, 03 Dec 2008 23:06:20 -0800, Techmann wrote:
I have a D.C. motor that spins just fine when I apply 12V to it.  The
motor has a 1/4" shaft and I would like to use it as a generator. When I
hook up a DC voltmeter to the leads and spin the shaft in the same
direction with my electric drill  (around 1000 RPM) the most I see out
of the motor is only .24 volts.  I am puzzled why I am not seeing close
to 12V output on this motor.  Can only certain kinds of DC motors be
used as generators?  Is it caused by the way the coils are wired up
internally and is there a way to test or change this so that it can be
made into a generator?  Thank you.

T.C.

It's probably a wound-field motor, instead of a permanent magnet motor.  
A wound-field machine will work just dandy as a generator, but you have
to supply field current.

If it goes the same direction no matter what direction you connect the
power then it's a wound-field motor.  If that's the case, then you want
to find out how to excite the field separately.  If it's a shunt field
then this will be easy, if it's a series field this will be difficult, or
at least oddball.

Does this motor have a nameplate?

--
Tim Wescott
Control systems and communications consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html

The nameplate says AiResearch Mfg Co. of Arizona, Inc.  Motor -
Aircraft Direct Current with Thermal Protection 24V System
Type BDIB
Dwg. No. 25226
HP 1/8
RPM 7500
AMPS 9.0

It measures about 4-1/2" long by 2-1/4" in diameter, has a 7-splined
1/4" shaft and appears to be a high-quality motor.

It has 2 wires coming out (red & green) plus the case ground.  When I
hook up battery (-) to the case and (+) to the red wire it turns CCW
(as looking at the shaft).  If I reverse the battery leads it still
turns CCW.  When I connect (+) to the green wire it turns CW.  If I
reverse the battery leads to the green wire and case ground it still
turns CW.  Between either red or green and the case there is 3.8 ohms
resistance and between the red and green wires there is 1 ohm
resistance.  I am guessing that if was running as a generator that the
red wire would be positive voltage relative to ground while the green
wire would be producing a negative voltage relative to ground.

As you mentioned, since it turns the same direction no matter which
way the polarity is it must be a wound-field. Now how would I
determine whether it's a series or shunt wound?  Another person wrote
that it's also possible to put the field
in parallel with the armature so it is supplied by its own voltage
(otherwise known as a parallel wound motor).

"With that type of motor, used as a generator, the iron in the field
has to retain a little residual magnetism to start it producing power,
and it sometimes helps if it is not under an electrical load until it
starts producing current.  A small permanent magnet can also be put on
part of the field to insure it starts (if the iron doesn't retain
enough magnetism - determined by the type of iron)"

This sounds neat since I wouldn't have to use an external battery
source to excite the field but where is the best place to locate the
magnet and how big/strong would it have to be?

Thank you,

T.C.

You're going to have to pop the end plate off at the very least to get
at the connections.  Most of the wound motors I've encountered have
been series wound.

The brushes are spring loaded and if you have access, take them out
before pulling the brush end off.

The choices are series, parallel, and compound (both - two field
windings on the poles).  A little searching on the I-net will tell you
about them.  Since you have a lead to reverse the motor it may have
two field windings (center tapped) and it is still a series wound -
not compound (compound: one field winding in series and one winding
across the armature)

As for locating the magnet . . . if it uses solid pole pieces or
laminated ones,  just shave a little metal off a pole piece and epoxy
a (large surface, thin, rare earth) magnet in.  

The gap between the armature and field should be small - it improves
efficiency up to a point, so don't grind away any more metal than you
have to.  

But get it wound in parallel and see if it works - you may not need
any magnet.
--

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My understanding is the field coil on a shunt-wound motor typically
has a resistance of several hundred ohms vs. the field coil on a
series-wound motor which is only a few ohms. For connecting the field
coil in parallel with the armature coil as you described, which type
of field coil would work best?

I don't know the answer to that. There are motors that can be wired

for either operation, so I would assume that they strike some
compromise. If you had a shunt wound motor it should probably
generate voltage and that isn't happening, so it might be series.

Another thing you mention that you have a reversing wire? I had one
of those (nice military surplus). The winding was in series - the
center tap connected to the armature brush and depending on which wire
you applied to power the direction of the field with respect to the
armature changed. The winding is tapped and all wound in the same
direction . . . so depending on whether the power went to the "start"
or "finish" the magnetic polarity changed.

In that case you could use both windings ignoring the tap to get a
high resistance shunt winding.

If I wanted to use a battery to supply voltage just to the field
winding and not connect it to the armature, it would seem that a shunt-
wound motor would be the much better choice since the coil has a
natural high reistance and thus it would require much less current
from the battery. Is my thinking correct here?

More or less. Magnetic field strength is greater with lower resistance
for the same volume of wire - for a motor. I don't know how that
translates to generators though.

Finally, if I wanted a regulated 12 volt output, having a separate
field winding would be desirable since I could vary the voltage across
the field coil to maintain a constant voltage output. As a side
topic, I have a Chrysler regulator from an old Dodge Van which has
just 2 pins on a rubber connector plus case ground. I checked the van
schematic and the pins connect directly across the field coil. What I
don't understand is how does the regulator know the output voltage of
the alternator if it doesn't have a sense lead?

Thanks again

Car alternators? The power is generated in the stationary outside
winding - three phase. The rotor is a rotating field - only two
wires. Some use brushes and the coil actually rotates - some use
rotating poles and stationary coil. Same principle.

But if you look on line you'll see several regulators of different
types. The internal ones - you have only two wires one to battery
plus and ground, and the whole thing is internal.

The external regulator still has a connection to the battery somewhere
and that's where voltage is sensed - the same wire from the diodes
(output) may also be the sense wire.

Some also use the "idiot light" as a resistor to tickle the rotor with
a little current - starts the alternator charging. It has a separate
set of diodes for the lamp in that case (just three lightweight
diodes)Light goes out when the voltage is coming from the alternator
to run the rotor - from the lamp when the speed is low or engine isn't
turning (or something is wrong, like bad brushes).

Look for a schematic for an external regulator and use that to excite
your field. I built a couple using only two transistors, zener, and
some resistors- very simple circuit.

http://jhau.maliwi.de/mot/voltreg.htm Has something similar to mine.

Mine is a little simpler still - and I used a pot to set the
charging voltage, two NPN bipolar transistors. Made one for my 72 BWM
motorcycle and another for a 1970 Toyota Land Cruiser - both had
electromechanical regulators initially.


http://www.amsterdamhouseboats.nl/voltage_regulator.htm way more
complicated than necessary but shows the extra diodes a car alternator
uses.

http://www.vtr.org/maintain/alternator-overview.shtml
Three transistor alternator regulator and shows the indicator lamp

http://www.kb-kbh.dk/shipslib/el_ombord/alternatorhandbook_ocr.pdf
The bible on alternators for sailors
--


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---= - Total Privacy via Encryption =---

 

[Techmann]

On Dec 5, 5:19 pm, default <defa...@defaulter.net> wrote:

On Fri, 5 Dec 2008 12:16:52 -0800 (PST), Techmann





Intheme...@yahoo.com> wrote:
On Dec 5, 10:50 am, default <defa...@defaulter.net> wrote:
On Thu, 4 Dec 2008 22:13:08 -0800 (PST), Techmann

Intheme...@yahoo.com> wrote:
On Dec 4, 8:12 pm, Tim Wescott <t...@seemywebsite.com> wrote:
On Wed, 03 Dec 2008 23:06:20 -0800, Techmann wrote:
I have a D.C. motor that spins just fine when I apply 12V to it.  The
motor has a 1/4" shaft and I would like to use it as a generator. When I
hook up a DC voltmeter to the leads and spin the shaft in the same
direction with my electric drill  (around 1000 RPM) the most I see out
of the motor is only .24 volts.  I am puzzled why I am not seeing close
to 12V output on this motor.  Can only certain kinds of DC motors be
used as generators?  Is it caused by the way the coils are wired up
internally and is there a way to test or change this so that it can be
made into a generator?  Thank you.

T.C.

It's probably a wound-field motor, instead of a permanent magnet motor.  
A wound-field machine will work just dandy as a generator, but you have
to supply field current.

If it goes the same direction no matter what direction you connect the
power then it's a wound-field motor.  If that's the case, then you want
to find out how to excite the field separately.  If it's a shunt field
then this will be easy, if it's a series field this will be difficult, or
at least oddball.

Does this motor have a nameplate?

--
Tim Wescott
Control systems and communications consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html

The nameplate says AiResearch Mfg Co. of Arizona, Inc.  Motor -
Aircraft Direct Current with Thermal Protection 24V System
Type BDIB
Dwg. No. 25226
HP 1/8
RPM 7500
AMPS 9.0

It measures about 4-1/2" long by 2-1/4" in diameter, has a 7-splined
1/4" shaft and appears to be a high-quality motor.

It has 2 wires coming out (red & green) plus the case ground.  When I
hook up battery (-) to the case and (+) to the red wire it turns CCW
(as looking at the shaft).  If I reverse the battery leads it still
turns CCW.  When I connect (+) to the green wire it turns CW.  If I
reverse the battery leads to the green wire and case ground it still
turns CW.  Between either red or green and the case there is 3.8 ohms
resistance and between the red and green wires there is 1 ohm
resistance.  I am guessing that if was running as a generator that the
red wire would be positive voltage relative to ground while the green
wire would be producing a negative voltage relative to ground.

As you mentioned, since it turns the same direction no matter which
way the polarity is it must be a wound-field. Now how would I
determine whether it's a series or shunt wound?  Another person wrote
that it's also possible to put the field
in parallel with the armature so it is supplied by its own voltage
(otherwise known as a parallel wound motor).

"With that type of motor, used as a generator, the iron in the field
has to retain a little residual magnetism to start it producing power,
and it sometimes helps if it is not under an electrical load until it
starts producing current.  A small permanent magnet can also be put on
part of the field to insure it starts (if the iron doesn't retain
enough magnetism - determined by the type of iron)"

This sounds neat since I wouldn't have to use an external battery
source to excite the field but where is the best place to locate the
magnet and how big/strong would it have to be?

Thank you,

T.C.

You're going to have to pop the end plate off at the very least to get
at the connections.  Most of the wound motors I've encountered have
been series wound.

The brushes are spring loaded and if you have access, take them out
before pulling the brush end off.

The choices are series, parallel, and compound (both - two field
windings on the poles).  A little searching on the I-net will tell you
about them.  Since you have a lead to reverse the motor it may have
two field windings (center tapped) and it is still a series wound -
not compound (compound: one field winding in series and one winding
across the armature)

As for locating the magnet . . . if it uses solid pole pieces or
laminated ones,  just shave a little metal off a pole piece and epoxy
a (large surface, thin, rare earth) magnet in.  

The gap between the armature and field should be small - it improves
efficiency up to a point, so don't grind away any more metal than you
have to.  

But get it wound in parallel and see if it works - you may not need
any magnet.
--

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---= - Total Privacy via Encryption =---- Hide quoted text -

- Show quoted text -

My understanding is the field coil on a shunt-wound motor typically
has a resistance of several hundred ohms vs. the field coil on a
series-wound motor which is only a few ohms.  For connecting the field
coil in parallel with the armature coil as you described, which type
of field coil would work best?

I don't know the answer to that.  There are motors that can be wired
for either operation, so I would assume that they strike some
compromise.  If you had a shunt wound motor it should probably
generate voltage and that isn't happening, so it might be series.

Another thing you mention that you have a reversing wire?  I had one
of those (nice military surplus).  The winding was in series - the
center tap connected to the armature brush and depending on which wire
you applied to power the direction of the field with respect to the
armature changed.  The winding is tapped and all wound in the same
direction . . . so depending on whether the power went to the "start"
or "finish" the magnetic polarity changed.

In that case you could use both windings ignoring the tap to get a
high resistance shunt winding.  

If I wanted to use a battery to supply voltage just to the field
winding and not connect it to the armature, it would seem that a shunt-
wound motor would be the much better choice since the coil has a
natural high reistance and thus it would require much less current
from the battery.  Is my thinking correct here?

More or less. Magnetic field strength is greater with lower resistance
for the same volume of wire - for a motor.  I don't know how that
translates to generators though.



Finally, if I wanted a regulated 12 volt output, having a separate
field winding would be desirable since I could vary the voltage across
the field coil to maintain a constant voltage output.  As a side
topic, I have a Chrysler regulator from an old Dodge Van which has
just 2 pins on a rubber connector plus case ground.  I checked the van
schematic and the pins connect directly across the field coil.  What I
don't understand is how does the regulator know the output voltage of
the alternator if it doesn't have a sense lead?

Thanks again

Car alternators?  The power is generated in the stationary outside
winding - three phase.  The rotor is a rotating field - only two
wires.  Some use brushes and the coil actually rotates - some use
rotating poles and stationary coil.  Same principle.

But if you look on line you'll see several regulators of different
types.  The internal ones - you have only two wires one to battery
plus and ground, and the whole thing is internal.

The external regulator still has a connection to the battery somewhere
and that's where voltage is sensed - the same wire from the diodes
(output) may also be the sense wire.

Some also use the "idiot light" as a resistor to tickle the rotor with
a little current - starts the alternator charging.  It has a separate
set of diodes for the lamp in that case (just three lightweight
diodes)Light goes out when the voltage is coming from the alternator
to run the rotor - from the lamp when the speed is low or engine isn't
turning (or something is wrong, like bad brushes).

Look for a schematic for an external regulator and use that to excite
your field.  I built a couple using only two transistors, zener, and
some resistors- very simple circuit.

http://jhau.maliwi.de/mot/voltreg.htm Has something similar to mine.

  Mine is a little simpler still - and I used a pot to set the
charging voltage, two NPN bipolar transistors.  Made one for my 72 BWM
motorcycle and another for a 1970 Toyota Land Cruiser - both had
electromechanical regulators initially.

http://www.amsterdamhouseboats.nl/voltage_regulator.htmway more
complicated than necessary but shows the extra diodes a car alternator
uses.

http://www.vtr.org/maintain/alternator-overview.shtml
Three transistor alternator regulator and shows the indicator lamp

http://www.kb-kbh.dk/shipslib/el_ombord/alternatorhandbook_ocr.pdf
The bible on alternators for sailors
--

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- Show quoted text -

Thanks for the great site links. I especially liked the boater's
alternator bible. I have a little book I bought called "Alternator
Secrets" which has a schematic for a simple two transistor regulator
circuit. I will probably start with that circuit and modify it as
needed. Right now though, I am going to start to take apart the motor
and see how the coils are wired.

Regards,

T.C.

 

[Jamie]

Techmann wrote:

On Dec 4, 8:12 pm, Tim Wescott <t...@seemywebsite.com> wrote:

On Wed, 03 Dec 2008 23:06:20 -0800, Techmann wrote:

I have a D.C. motor that spins just fine when I apply 12V to it. The
motor has a 1/4" shaft and I would like to use it as a generator. When I
hook up a DC voltmeter to the leads and spin the shaft in the same
direction with my electric drill (around 1000 RPM) the most I see out
of the motor is only .24 volts. I am puzzled why I am not seeing close
to 12V output on this motor. Can only certain kinds of DC motors be
used as generators? Is it caused by the way the coils are wired up
internally and is there a way to test or change this so that it can be
made into a generator? Thank you.

T.C.

It's probably a wound-field motor, instead of a permanent magnet motor.
A wound-field machine will work just dandy as a generator, but you have
to supply field current.

If it goes the same direction no matter what direction you connect the
power then it's a wound-field motor. If that's the case, then you want
to find out how to excite the field separately. If it's a shunt field
then this will be easy, if it's a series field this will be difficult, or
at least oddball.

Does this motor have a nameplate?

--
Tim Wescott
Control systems and communications consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html


The nameplate says AiResearch Mfg Co. of Arizona, Inc. Motor -
Aircraft Direct Current with Thermal Protection 24V System
Type BDIB
Dwg. No. 25226
HP 1/8
RPM 7500
AMPS 9.0

It measures about 4-1/2" long by 2-1/4" in diameter, has a 7-splined
1/4" shaft and appears to be a high-quality motor.

It has 2 wires coming out (red & green) plus the case ground. When I
hook up battery (-) to the case and (+) to the red wire it turns CCW
(as looking at the shaft). If I reverse the battery leads it still
turns CCW. When I connect (+) to the green wire it turns CW. If I
reverse the battery leads to the green wire and case ground it still
turns CW. Between either red or green and the case there is 3.8 ohms
resistance and between the red and green wires there is 1 ohm
resistance. I am guessing that if was running as a generator that the
red wire would be positive voltage relative to ground while the green
wire would be producing a negative voltage relative to ground.

As you mentioned, since it turns the same direction no matter which
way the polarity is it must be a wound-field. Now how would I
determine whether it's a series or shunt wound? Another person wrote
that it's also possible to put the field
in parallel with the armature so it is supplied by its own voltage
(otherwise known as a parallel wound motor).

"With that type of motor, used as a generator, the iron in the field
has to retain a little residual magnetism to start it producing power,
and it sometimes helps if it is not under an electrical load until it
starts producing current. A small permanent magnet can also be put on
part of the field to insure it starts (if the iron doesn't retain
enough magnetism - determined by the type of iron)"

This sounds neat since I wouldn't have to use an external battery
source to excite the field but where is the best place to locate the
magnet and how big/strong would it have to be?

Thank you,

T.C.

That is a series motor, it'll even operate on A.C.

http://webpages.charter.net/jamie_5"

 

[Rich Grise]

On Thu, 04 Dec 2008 17:02:39 +0000, Clint Sharp wrote:

In message <gh82i1$l3n$1@reversiblemaps.ath.cx>, Jasen Betts
jasen@xnet.co.nz> writes
the easiest kind of DC motor to use as a genetator is one with both
brushes and permanent magnets, other kinds can be used but will probably
need to be modified.

All kinds of DC motor when used as a generator will need the output
rectifying or measuring with an AC voltmeter.

If you find this to be true, then what you're measuring is not a DC
generator.

Hope This Helps!
Rich

 

[Rich Grise]

On Thu, 04 Dec 2008 22:13:08 -0800, Techmann wrote:

The nameplate says AiResearch Mfg Co. of Arizona, Inc. Motor - Aircraft
Direct Current with Thermal Protection 24V System Type BDIB
Dwg. No. 25226
HP 1/8
RPM 7500
AMPS 9.0

It measures about 4-1/2" long by 2-1/4" in diameter, has a 7-splined 1/4"
shaft and appears to be a high-quality motor.

I'd be willing to bet real money that it's series-wound.

Cheers!
Rich

 

[Clint Sharp]

In message <Po-dnSKT9tOS4qXUnZ2dnUVZ_jidnZ2d@web-ster.com>, Tim Wescott
<tim@seemywebsite.com> writes

On Thu, 04 Dec 2008 17:02:39 +0000, Clint Sharp wrote:

In message <gh82i1$l3n$1@reversiblemaps.ath.cx>, Jasen Betts
jasen@xnet.co.nz> writes
the easiest kind of DC motor to use as a genetator is one with both
brushes and permanent magnets, other kinds can be used but will
probably need to be modified.
All kinds of DC motor when used as a generator will need the output
rectifying or measuring with an AC voltmeter.

Absolutely totally wrong.

Go check your science.

My apologies, you are of course absolutely correct, I have no idea what

I was thinking, except that I probably wasn't thinking. For some reason
I thought it acted like an alternator with slip rings, forgetting about
commutator.
--
Clint Sharp