Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
D C motor. Which of these two drawing are correct to run dc motor 1
- Thread starter didnotrun
- Start date
davidbeach
Electrical
Make a PDF of the drawing. More people will be willing to open a PDF than a random DOCX file.
- Thread starter
- #4
- Moderator
- #5
Both. One is for a "Series Wound" motor, the other is for a "Shunt Wound" motor. Series wound are used where you need high starting torque and less torque as speed increases, such as traction motors, but NEVER start unloaded (because they can run away on you). Shunt wound are used when you need constant torque and/or precise speed control but don't need that high initial torque to overcome high inertia/"stiction". The DC motors are different, you must know what you have before connecting them. The nameplate should tell you.
" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden
" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden
ASSuming the blue fields are shunt fields, um, er, those both look compound wound to me; based on conventional, and not electron, flow, the flow is from left to right through all components, so the characteristics of both connections, including direction of rotation, are identical. The only difference between the two drawings is the sequence; in the upper drawing, the current first flows through the series windings, then the armature, then the interpole windings; in the lower drawing, the current first flows through the series windings, then the interpole windings, then the armature.
Right?
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
Right?
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
- Thread starter
- #8
Both will work identically; pick one. Just ensure the motor rotates the fan in the correct direction; if not, simply reverse the connections to, and therefore the current flow through, the armature.
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
- Moderator
- #10
If you reverse the current flow through the armature and not the inter-poles, the motor will run but it will spark a lot.
The inter-poles aid in keeping the commutation at the neutral point as the load changes.
Further to that; if the motor does spark a lot, try reversing the inter-poles.
Bill
--------------------
"Why not the best?"
Jimmy Carter
The inter-poles aid in keeping the commutation at the neutral point as the load changes.
Further to that; if the motor does spark a lot, try reversing the inter-poles.
Bill
--------------------
"Why not the best?"
Jimmy Carter
- Moderator
- #12
Most diagrams that I have seen do not show the interpoles. They are permanently connected to the armature and considered part of the armature circuit. The typical circuit is A1, brush, armature, brush, interpole, A2
The interpoles are there even though they are not shown on the connection diagram. The permanent, often buried connection between the armature and the interpole avoids the possibility of a reverse connected interpole.
Bill
--------------------
"Why not the best?"
Jimmy Carter
The interpoles are there even though they are not shown on the connection diagram. The permanent, often buried connection between the armature and the interpole avoids the possibility of a reverse connected interpole.
Bill
--------------------
"Why not the best?"
Jimmy Carter
Thanks again, Bill.
The OP's diagram showed the interpole leads brought out; under what circumstances might reversing interpole current flow be required? One possible scenario that comes to mind would be changing a given machine's use from motor to generator or vice versa...but I can't wrap my head around what that would do to armature reaction...
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
The OP's diagram showed the interpole leads brought out; under what circumstances might reversing interpole current flow be required? One possible scenario that comes to mind would be changing a given machine's use from motor to generator or vice versa...but I can't wrap my head around what that would do to armature reaction...
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
- Thread starter
- #14
Yes, the interpole is connected to one of the brush box and from other brush box lead straight out (only two brushes boxes on this machine). Hence there are six leads out to the terminal box and the connection drawing has gone missing, that is why help is required.
New drawing as per leads out and motor name plate photo attached.
New drawing as per leads out and motor name plate photo attached.
- Moderator
- #15
Never, cr.
There is a neutral point for the brushes where the voltage across the face of the brush is at a minimum or null as the brush passes from one commutator segment to the next segment. As the armature current increases, the magnetic field set up by the armature current interacts with the main magnetic field and distorts the flux path.
The position and strength of the inter-poles is such as to push the main field flux back to the null position.
If the current trough the armature i reversed, the distortion of the field is reversed, but the current through the inter-pole is also reversed and the corrective action is the same.
Motor versus generator:
I like to say that there is only a few Volts or a few RPM between a motor and a generator.
The back EMF is typically close to the applied voltage.
If the motor speed is increased by an overhauling load, the back EMF increases. s the back EMF matches and exceeds the pplied voltage, the motor smoothly transitions to a generator. When the motor is powered by batteries or a 2 or 4 quadrant controller, the regeneration will oppose the increased speed and work will be done.
If the motor is not able to send current back through the source, there will be no opposition to the speed increase and the back EMF will rise in proportion to the increase in speed.
Similarly if an overhauling load or load inertia keeps the motor speed more or less constant and the applied voltage is reduced below the value of the back EMF the motor will smoothly transition to a generator as the applied voltage drops below the value of the back EMF.
The action of the inter-poles remains basically the same under all conditions.
Bill
--------------------
"Why not the best?"
Jimmy Carter
There is a neutral point for the brushes where the voltage across the face of the brush is at a minimum or null as the brush passes from one commutator segment to the next segment. As the armature current increases, the magnetic field set up by the armature current interacts with the main magnetic field and distorts the flux path.
The position and strength of the inter-poles is such as to push the main field flux back to the null position.
If the current trough the armature i reversed, the distortion of the field is reversed, but the current through the inter-pole is also reversed and the corrective action is the same.
Motor versus generator:
I like to say that there is only a few Volts or a few RPM between a motor and a generator.
The back EMF is typically close to the applied voltage.
If the motor speed is increased by an overhauling load, the back EMF increases. s the back EMF matches and exceeds the pplied voltage, the motor smoothly transitions to a generator. When the motor is powered by batteries or a 2 or 4 quadrant controller, the regeneration will oppose the increased speed and work will be done.
If the motor is not able to send current back through the source, there will be no opposition to the speed increase and the back EMF will rise in proportion to the increase in speed.
Similarly if an overhauling load or load inertia keeps the motor speed more or less constant and the applied voltage is reduced below the value of the back EMF the motor will smoothly transition to a generator as the applied voltage drops below the value of the back EMF.
The action of the inter-poles remains basically the same under all conditions.
Bill
--------------------
"Why not the best?"
Jimmy Carter
-
1
- #16
- Moderator
- #17
- Thread starter
- #18
Direct Current motors have numerous simultaneous circumstances required for them to operate perfectly.
Your original question in January related to the motor’s connection requirement.
Now, you are raising a new question related to brush burning, arching and sparking of the brushes.
The photo is very telling and thank you for posting the picture.
Can I toss some questions back at ‘cha?
Back in January, when you were asking about how the motor should be connected, what originally happened
to the motor that caused you to dismantle the motor and then post a question here related to the motor’s connection?
What was the original reason or problem the motor was exhibiting in the very beginning before you came here looking for answers related to your connection uncertainty?
Fill in these blanks if you can.
John
Your original question in January related to the motor’s connection requirement.
Now, you are raising a new question related to brush burning, arching and sparking of the brushes.
The photo is very telling and thank you for posting the picture.
Can I toss some questions back at ‘cha?
Back in January, when you were asking about how the motor should be connected, what originally happened
to the motor that caused you to dismantle the motor and then post a question here related to the motor’s connection?
What was the original reason or problem the motor was exhibiting in the very beginning before you came here looking for answers related to your connection uncertainty?
Fill in these blanks if you can.
John
- Thread starter
- #20
Back in January someone had dismantled the motor without marking the leads, nothing serious but seeking confirmation as only one person who in the winder and all other are mechanical oriented.
When the job came in, brush wearing quickly on this motor only from its history, on testing various parts of motor found the armature faulty and was send for rewind, and on assembly test confirming all parts and armature in good condition.
On test there is a spark coming out say two every minute not continuous arcing or sparking, otherwise the whole job is running cool to touch even after eight hours of continuous running, hence further info to get more knowledge.
When the job came in, brush wearing quickly on this motor only from its history, on testing various parts of motor found the armature faulty and was send for rewind, and on assembly test confirming all parts and armature in good condition.
On test there is a spark coming out say two every minute not continuous arcing or sparking, otherwise the whole job is running cool to touch even after eight hours of continuous running, hence further info to get more knowledge.
- Status
Similar threads
- Question
- Locked
- Question
- Locked
- Question
- Locked
- Question