DC Starter wiring question-curiosity only!

[stevieb49829]

There's been a lot of discussion around converting to 12V negative ground systems. Common knowledge is that the starter will still turn in the correct direction, even when you switch a positive ground to a negative ground system. Why doesn't the starter turn backwards when you switch the current flow? I'm not an electrician, so can someone explain this to me in not-too-technical terms? steve

 

[JMOR]

There's been a lot of discussion around converting to 12V negative ground systems. Common knowledge is that the starter will still turn in the correct direction, even when you switch a positive ground to a negative ground system. Why doesn't the starter turn backwards when you switch the current flow? I'm not an electrician, so can someone explain this to me in not-too-technical terms? steve

You switch current flow direction in BOTH the fields AND armature.

 

[used red MN]

A DC motor with permanent magnet stator fields in the case will switch its direction when polarity is switched. I got a lot of my self-learned electrical base knowledge from playing/experimenting with parts from battery operated toys I disassembled. I think all battery operated motors from toys were permanent magnet motors. So the concept of a DC motor that did not reverse when the polarity changed was a bit out of my “learned” norm. But I soon learned as JMOR points out if the DC motor has “wound” stators the current flow switches in them as well and the rotation remains the same. I am not sure that gives much explanation in the terms of why. It is all about the magnetic “pull” of the energized electromagnets in the armature and their reaction with the stationary permanent magnets. The magnetic poles (N & S) stay the same in a permanent magnet. When the stators (stationary magnets) are wound or are an electromagnet the poles switch when the polarity is changed. So the switched “magnetic poles” in the armature react or match the same action or attraction so the armature is pulled in the same direction. If this does not help reply and I can look for a video this evening that explains this better.

 

[Janicholson]

One more thing. series wound motors have the field and armature connected from one to the other, like old Christmas tree lights the power flows in one light and then to the next. Parallel wound motors have the field and armature connected like a pair of horses pulling a load. The same as Christmas tree lights that stay lit when one bulb burns out. These are sometimes called Universal motors. Common electric motors come in 10 categories that get more complex as the count goes toward 10, and there are sub categories within the 10. Jim

 

[rvirgil_KS]

There's been a lot of discussion around converting to 12V negative ground systems. Common knowledge is that the starter will still turn in the correct direction, even when you switch a positive ground to a negative ground system. Why doesn't the starter turn backwards when you switch the current flow? I'm not an electrician, so can someone explain this to me in not-too-technical terms? steve

Check out this web site for a 1946 Delco Remy manual that gives explanation of starter motor operation

chevy(dot)oldcarmanualproject(dot)com/electrical/49dr324/1m1001(dot) put a dot . where it says and add htm at end

For complete manual try deleting everything after 324

 

[stevieb49829]

I read the link rvirgil sent with his reply, and it provided a good basis for understanding what the rest of you said. I was of the same mindset as the young version of used red, thinking the stator fields were permanent, and that a switch of current direction in the armature would change rotation. Jim's and used red's further explanations helped me to understand that without permanent magnets, the electrons might change direction, but both the stator and armature change their electron directions and cancel out the tendency to reverse direction. Thank you. I'm still curious of how you would reverse the rotation direction then, on a series-wound motor? Is it a matter of changing where the connections are in the series? steve

 

[John T]

Good question Steve Why doesn't the starter turn backwards when you switch the current flow? I'm not an electrician, so can someone explain this to me in not-too-technical terms? steve

A typical old tractor DC starter motor uses a current generated ELECTROmagnetic field unlike a permanent magnet field starter like some lawn mowers and other vehicles use. Even when you swap polarity on such a motor it rotates THE SAME DIRECTION because you have not changed the North/South magnetic polarity relationship BETWEEN the Field and Armature. If you got inside there and somehow reversed the field winding side to side which changes the North/South Magnetic polarity the Arm to Field relationship changes and it would turn the opposite direction. The Armature rotates inside a magnetic field and in the old tractor starter that magnetic field is created by passing current through field windings (DIRECTION OF CURRENT AFFECTS NORTH/SOUTH MAGNETIC POLARITY) while in a permanent magnet field starter its simply a high strength permanent magnet thats used so if you reverse its polarity the rotation changes.

So you asked for not-to-technical, but sorry, that's the best this 40 + year ago Century Electric Motor Company Engineer has to offer lol it turns the SAME direction because the Armature to Field magnetic relationship has not changed.

PS a DC motor and generator are basically the same thing. If you put energy IN it rotates, but if rotated it puts energy OUT.

Im rusty on this NO WARRANTY BASED ON OLD RECOLLECTION GRRRRRRRRRRR so see what other tractor mechanics and engineers can add as it cant be explained very well in only a few sentences, the more the merrier as far as explanations are concerned to help you understand...Fun to hear other explanations

John T Live in the RV in Avon Park Florida

 

[stevieb49829]

Good question Steve Why doesn't the starter turn backwards when you switch the current flow? I'm not an electrician, so can someone explain this to me in not-too-technical terms? steve

A typical old tractor DC starter motor uses a current generated ELECTROmagnetic field unlike a permanent magnet field starter like some lawn mowers and other vehicles use. Even when you swap polarity on such a motor it rotates THE SAME DIRECTION because you have not changed the North/South magnetic polarity relationship BETWEEN the Field and Armature. If you got inside there and somehow reversed the field winding side to side which changes the North/South Magnetic polarity the Arm to Field relationship changes and it would turn the opposite direction. The Armature rotates inside a magnetic field and in the old tractor starter that magnetic field is created by passing current through field windings (DIRECTION OF CURRENT AFFECTS NORTH/SOUTH MAGNETIC POLARITY) while in a permanent magnet field starter its simply a high strength permanent magnet thats used so if you reverse its polarity the rotation changes.

So you asked for not-to-technical, but sorry, that's the best this 40 + year ago Century Electric Motor Company Engineer has to offer lol it turns the SAME direction because the Armature to Field magnetic relationship has not changed.

PS a DC motor and generator are basically the same thing. If you put energy IN it rotates, but if rotated it puts energy OUT.

Im rusty on this NO WARRANTY BASED ON OLD RECOLLECTION GRRRRRRRRRRR so see what other tractor mechanics and engineers can add as it cant be explained very well in only a few sentences, the more the merrier as far as explanations are concerned to help you understand...Fun to hear other explanations

John T Live in the RV in Avon Park Florida

Thanks, John. Then IF I was to go inside this DC motor, and reverse the wiring to the stator coils, the motor rotation would reverse, right? In theory!! I'm not that bored, yet!!! steve

 

[Janicholson]

Thanks, John. Then IF I was to go inside this DC motor, and reverse the wiring to the stator coils, the motor rotation would reverse, right? In theory!! I'm not that bored, yet!!! steve

Stator is a term pretty much reserved for alternators. and pulse controlled motors. If you mean field, yes. The problem with that is the leads are often ribbon shaped copper and have leads that work to locations that are not easily reversed. but it would reverse the motor. Not all brush holders are designed to allow reverse rotation, so that may be a separate issue. Jim

 

[stevieb49829]

Stator is a term pretty much reserved for alternators. and pulse controlled motors. If you mean field, yes. The problem with that is the leads are often ribbon shaped copper and have leads that work to locations that are not easily reversed. but it would reverse the motor. Not all brush holders are designed to allow reverse rotation, so that may be a separate issue. Jim

That makes a lot of sense Jim. I've been inside a dc starter or two, and yes they are usually copper bands, and not wires, on the field windings. See, I even learned the correct terminology instead of 'stator'.

 

[John T]

Thanks, John. Then IF I was to go inside this DC motor, and reverse the wiring to the stator coils, the motor rotation would reverse, right? In theory!! I'm not that bored, yet!!! steve

Im in the same camp as Professor Jim...Sort of mixing apples and oranges DC versus AC, but basically a DC Field is the STATIONARY component, while the DC Armature ROTATES.........If the stationary Field wire ends were somehow reversed IF POSSIBLE TO GET TO THEM ???? YES it would reverse.

John T

 

[used red MN]

Stator is a term pretty much reserved for alternators. and pulse controlled motors. If you mean field, yes. The problem with that is the leads are often ribbon shaped copper and have leads that work to locations that are not easily reversed. but it would reverse the motor. Not all brush holders are designed to allow reverse rotation, so that may be a separate issue. Jim

I got the stator term from this diagram and ran with it.
DC motor info
I thought the internet was smarter than me providing a more technical term. Field magnet or coil is how I would have normally referred to them. I was moving through that pretty quick and the alternator and stator connection did not pop up in the old gray matter.

 

[Tim PloughNman Daley]

There's been a lot of discussion around converting to 12V negative ground systems. Common knowledge is that the starter will still turn in the correct direction, even when you switch a positive ground to a negative ground system. Why doesn't the starter turn backwards when you switch the current flow? I'm not an electrician, so can someone explain this to me in not-too-technical terms? steve

Starter Motors don't care if 6V or 12V and will work on either one, can only turn in one direction, and it matters which system you have. FYI: ALL FORD 9N & 2N's used a 6V, 1-WIRE STARTER MOTOR with NO RELAY (SOLENOID). The 8N and all after revamped to a 3-Wire 6V Starter Motor and used a RELAY/SOLENOID. Know which is which. SOLENOIDS are different - it matters. Incorrect wiring accounts for 99.98% of all non-starting issues. and 12V conversions done wrong are often the culprit. If starter motor just clicks at start up, chances are your battery is weak or dead. Get it tested.

Tim Daley (MI)

 

[John T]

Starter Motors don't care if 6V or 12V and will work on either one, can only turn in one direction, and it matters which system you have. FYI: ALL FORD 9N & 2N's used a 6V, 1-WIRE STARTER MOTOR with NO RELAY (SOLENOID). The 8N and all after revamped to a 3-Wire 6V Starter Motor and used a RELAY/SOLENOID. Know which is which. SOLENOIDS are different - it matters. Incorrect wiring accounts for 99.98% of all non-starting issues. and 12V conversions done wrong are often the culprit. If starter motor just clicks at start up, chances are your battery is weak or dead. Get it tested.

Tim Daley (MI)

Great info for the Ford people. I’ve used a lot of old 6 volt starters on 12 volts they spun very fast and can be hard on starter drives. When I tried to use a 12 volt start on 6 volts however they cranked slowwwww. Just like some old cars and tractors a simple high current mechanical push switch suffices while bigger harde to crank engines used an electric solenoid of course being an electromagnetic field starter motor they turn the same direction regardless of polarity. Fun sparky chatting. John T