Interesting Motor

[mbrownn]

It looks like a nice motor. Similar in construction to automotive engine cranking motors or pump motors for truck equipments like snow plows, lift gates, etc. Those types of armatures can be wound several different ways, one of which is 4 pole 2 circuit called wave wound. This wave wound armature needs an odd number of coils and commutator segments.

Correct, The reason they put an odd number of coils in the armature is to prevent harmonics and resonances.

[Hiwater]

Here's a little video about the motor I picked up on eBay. Not sure it will work, as it has 41 sections on the commutator. But it does have four coils and two sets of brushes. I imagine a proper rotor with the right number of commutator sections could be machined that would fit this motor.

eBay Motor - YouTube

Dave

That looks like a golf cart starter generator, I have used the generator coils in a standard GM generator. The ones I had were 1.6 ohms. There 2 different sizes of generator coils for those. The smaller ones wont put out that much. If I remember right about 35 volts per coil. The larger ones will put out 120 volts.They just about light 3-100 watt bulbs to full brightness.

This motors are fun to work with. The brush end cap has its disadvantages.

[Turion]

shylo,
Yes, it's 41 segments on the commutator. Counted it three times to make sure. Like I said, I might have to find a different rotor and commutator to work with this motor, or have one machined.

[mbrownn]

shylo,
Yes, it's 41 segments on the commutator. Counted it three times to make sure. Like I said, I might have to find a different rotor and commutator to work with this motor, or have one machined.

In this video he shows how to wind the armature. although he connects to the nearest commutator segment instead of at 90 degrees. He also points out one of the compromises in a standard armature which creates increased BEMF and makes it unsuitable for my design. Thirdly he points out a problem with pole width on the armature, this isn’t a problem with standard motors but is a problem with my design.

https://www.youtube.com/watch?v=Q9CL...etailpage#t=99

[bistander]

Correct, The reason they put an odd number of coils in the armature is to prevent harmonics and resonances.

On the 4 pole simplex wave winding (a closed 2 path circuit), the odd number is a geometric requirement. There may be other benefits as you mention. Self equalization is another benefit over the lap winding (4 paths and even number of coils and comm segments). This eliminates the need for equalizer connections behind the commutator.

[mbrownn]

On the 4 pole simplex wave winding (a closed 2 path circuit), the odd number is a geometric requirement. There may be other benefits as you mention. Self equalization is another benefit over the lap winding (4 paths and even number of coils and comm segments). This eliminates the need for equalizer connections behind the commutator.

The problem with these windings are reduced torque, increased BEMF and no possibility of extracting inductive kickback. Its good for speed control and reducing arcing at the brushes. The advantages of a simple winding are the reverse of this. What was considered the big disadvantage was the arcing but these days we can extract that energy and use it elsewhere.

[bistander]

Well, we're not even sure if this machine is a motor or a generator. Perhaps the OP could provide the eBay number or link.

The problem with these windings are reduced torque, increased BEMF and no possibility of extracting inductive kickback.

I see no "problems". Without increasing the amount of copper, you could not change the armature winding to get more torque. The BEMF is likely appropriate for the application hence the reason this winding was chosen. And any armature inductance contributes to reactance with the alternating current in the armature circuit which is no problem. Extracting any other than shaft power from an intermittent duty motor is a losing proposition. If the machine is a generator, you're already taking all the generated electrical power.

[mbrownn]

I see no "problems". Without increasing the amount of copper, you could not change the armature winding to get more torque. The BEMF is likely appropriate for the application hence the reason this winding was chosen. And any armature inductance contributes to reactance with the alternating current in the armature circuit which is no problem. Extracting any other than shaft power from an intermittent duty motor is a losing proposition. If the machine is a generator, you're already taking all the generated electrical power.

I think you are overlooking a few points. BEMF is used as a means of controlling a motor, without it they would tend to accelerate to self destruction. I have taken this control off this device.

In lap wound armatures we have currents in adjacent wires going in opposite directions, this is a compromise that also limits torque to some extent. A simple armature removes this compromise.

Lap and wave wound armatures are good at what they do but are a design compromise to reduce arcing.

[bistander]

I have taken this control off this device.

Hi mbrownn,

I was referring to the machine shown in the video, post #56. So your statement makes no sense to me.

I think you are overlooking a few points. BEMF is used as a means of controlling a motor, without it they would tend to accelerate to self destruction.

BEMF is half of the equation for the power converted from mechanical to electrical (generator) or from electrical to mechanical (motor). That conversion power is the generated voltage (BEMF) times the armature current. Without BEMF, a motor would not rotate due to an electric input.

In lap wound armatures we have currents in adjacent wires going in opposite directions, this is a compromise that also limits torque to some extent. A simple armature removes this compromise.

In a properly wound lap armature (or wave wound), all the adjacent wires under a particular field pole conduct current in the same direction. Wires in the armature conducting currents in opposite directions are separated by the wires of coils being commutated which are in the interpolar region where there is little to no flux so they have a minimal influence on torque production. In other words, practically all armature conductors (wires) conducting current contribute to positive torque production.

Can you define what you mean by "simple armature"? Thanks.

bi

edit: Here is a link to a ppt file showing the lap and wave windings. http://www.google.com/url?sa=t&rct=j...96041959,d.cGU

[mbrownn]

Hi mbrownn,

I was referring to the machine shown in the video, post #56. So your statement makes no sense to me.

I am referring to the device this thread is about.

BEMF is half of the equation for the power converted from mechanical to electrical (generator) or from electrical to mechanical (motor). That conversion power is the generated voltage (BEMF) times the armature current. Without BEMF, a motor would not rotate due to an electric input.

Easy to get confused here as we have both motoring functions and generating functions in the same device, just as you do in a universal type motor, but the positions where BEMF are generated have been reduced. In the last sentence do you mean EMF? It does not make sense to me that BEMF, the force that opposes applied current, is the force that causes a motor to turn.

In a properly wound lap armature (or wave wound), all the adjacent wires under a particular field pole conduct current in the same direction. Wires in the armature conducting currents in opposite directions are separated by the wires of coils being commutated which are in the interpolar region where there is little to no flux so they have a minimal influence on torque production. In other words, practically all armature conductors (wires) conducting current contribute to positive torque production.

The interpolar region is exactly where I put the powered field coil, and is the reason for little or no BEMF generation in that coil, but in a wave wound armature all the coils are connected all be it to the brush that may be shorting them, so my field coil will induce an EMF in those coils causing drag. This is why a simple armature with non interconnecting coils is used. Not only that, it also explains why this simple armature produced more torque than a wave wound armature. If the coil is open circuit we have no current and no drag, nor can that coil induce a BEMF in an adjacent coil.

Can you define what you mean by "simple armature"? Thanks.

A simple armature is where the coils are connected to commutator bars at 180 degrees mechanical from each other, wound splitting the rotor in half ie 50,50 and are not connected to any other coil on the armature. It is the simplest form of winding an armature, as shown is simple motor explanation diagrams, just as you would expect a person with no motor knowledge to wind. I did post a link to a video on this somewhere but I will post that link here too http://www.energeticforum.com/redire...lpage%23t%3D99

Here is a link to a ppt file showing the lap and wave windings. http://www.google.com/url?sa=t&rct=j...96041959,d.cGU

Thanks for posting this link, hopefully people will be able to see what we are discussing and why a lap or wave armature would not perform as well in my device.

Hope this clears up any misunderstanding about the armature I use.

[citfta]

Mbrownn,

If you have a few minutes would you please look at the last post I just made in the Open Discussion thread. I didn't want to clutter up this thread with that post but would like your opinion.

Thanks,
Carroll

[bistander]

Bemf

BEMF is half of the equation for the power converted from mechanical to electrical (generator) or from electrical to mechanical (motor). That conversion power is the generated voltage (BEMF) times the armature current. Without BEMF, a motor would not rotate due to an electric input.

In the last sentence do you mean EMF? It does not make sense to me that BEMF, the force that opposes applied current, is the force that causes a motor to turn.

Actually BEMF is confusing. That is why I like to use "generated voltage" or Eg (E_sub_g). Eg is present in any conductor moving in the presence of a magnetic field (commonly viewed as cutting lines of flux). This generated voltage (Eg) in the conductor (or coil) is present regardless of the current in the conductor. Current can be either direction or zero and Eg will still exist in the conductor cutting flux.

So this generated voltage (Eg) occurs in the armature of a motor or generator. It is calculated (or measured) exactly the same way whether it is a motor or generator. It actually is the same physical attribute whether in a motor or in a generator. I guess you call that generated voltage (Eg) the BEMF only in the motor (because it opposes the current flow) and not in the generator where it sources the current flow. Confusing to me because it is the same thing. But whatever.

My point was that whether a motor or generator, this generated voltage (Eg) times the armature current (Ia) is equal to the power converted (Pconv). So in the motor, you have the electrical losses (IČR) subtracted from the electric input power to give you the power converted at the air gap (Pconv) and then the rotational losses (Iron and friction) subtracted to yield the mechanical output power on the shaft. From the generator viewpoint, the rotational losses subtract from the input shaft power and the IČR from the Pconv. Either way, Pconv = Eg * Ia.

With the motor you have an applied voltage, Vm. I guess what you call EMF. In the motor you have the voltage drop due to resistance (and brush). Then you have the generated voltage, Eg (you call BEMF). Both the voltage drop across the resistance and the Eg oppose the applied voltage, Vm. The electrical power input to the motor is not the power converted to mechanical power. Some of it is lost as heat in the resistance. In fact, at stall, all of the electric input power is lost as heat and none is converted to mechanical power. So what is converted to mechanical power? The generated voltage (Eg or BEMF) times the armature current.

continued in next post

[bistander]

continued from previous post

In circuits in general, when you want to transfer power from one device to another, their potentials must oppose. For instance if you want to charge a battery, the battery voltage must oppose the source voltage (charger). That way the power from the source is delivered to the battery, minus the resistive losses in the circuit and internal in the battery.

Regarding my last sentence "Without BEMF, a motor would not rotate due to an electric input." It is kind of a chicken and egg sort of thing. If the motor rotates, it generates a voltage in the armature. If there is no voltage generated (Eg or BEMF) in the armature, there is no rotation. If there is no rotation, there is no BEMF. I am making the assumption you're not turning the shaft by other means or changing the flux.

Hope that explains it.

bi

[mbrownn]

Actually BEMF is confusing. That is why I like to use "generated voltage" or Eg (E_sub_g). Eg is present in any conductor moving in the presence of a magnetic field (commonly viewed as cutting lines of flux). This generated voltage (Eg) in the conductor (or coil) is present regardless of the current in the conductor. Current can be either direction or zero and Eg will still exist in the conductor cutting flux.

Correct

So this generated voltage (Eg) occurs in the armature of a motor or generator. It is calculated (or measured) exactly the same way whether it is a motor or generator. It actually is the same physical attribute whether in a motor or in a generator. I guess you call that generated voltage (Eg) the BEMF only in the motor (because it opposes the current flow) and not in the generator where it sources the current flow. Confusing to me because it is the same thing. But whatever.

I have to double check with this too, generally I call generated voltage EMF. BEMF is the voltage generated that opposes a supply emf in a motor.

My point was that whether a motor or generator, this generated voltage (Eg) times the armature current (Ia) is equal to the power converted (Pconv). So in the motor, you have the electrical losses (IČR) subtracted from the electric input power to give you the power converted at the air gap (Pconv) and then the rotational losses (Iron and friction) subtracted to yield the mechanical output power on the shaft. From the generator viewpoint, the rotational losses subtract from the input shaft power and the IČR from the Pconv. Either way, Pconv = Eg * Ia.

With the motor you have an applied voltage, Vm. I guess what you call EMF. In the motor you have the voltage drop due to resistance (and brush). Then you have the generated voltage, Eg (you call BEMF). Both the voltage drop across the resistance and the Eg oppose the applied voltage, Vm. The electrical power input to the motor is not the power converted to mechanical power. Some of it is lost as heat in the resistance. In fact, at stall, all of the electric input power is lost as heat and none is converted to mechanical power. So what is converted to mechanical power? The generated voltage (Eg or BEMF) times the armature current.

n circuits in general, when you want to transfer power from one device to another, their potentials must oppose. For instance if you want to charge a battery, the battery voltage must oppose the source voltage (charger). That way the power from the source is delivered to the battery, minus the resistive losses in the circuit and internal in the battery.n circuits in general, when you want to transfer power from one device to another, their potentials must oppose. For instance if you want to charge a battery, the battery voltage must oppose the source voltage (charger). That way the power from the source is delivered to the battery, minus the resistive losses in the circuit and internal in the battery.

Im not going to check your mathematics, I assume its all textbook, it sounds as though were on the same page.

Regarding my last sentence "Without BEMF, a motor would not rotate due to an electric input." It is kind of a chicken and egg sort of thing. If the motor rotates, it generates a voltage in the armature.

Correct.

If there is no voltage generated (Eg or BEMF) in the armature, there is no rotation.

Correct again assuming you have a standard motor and there is residual magnetism.

If there is no rotation, there is no BEMF. I am making the assumption you're not turning the shaft by other means or changing the flux.

Hope that explains it.

bi

The point is, I set the motor part up so it wont turn, its an energiser. It only puts magnetic flux into the magnetic circuit. It energises the magnetic circuit. The only reason it turns is because of the location of the generator shoe. It is the same force that causes generation, that causes torque.

As we are not motoring in a conventional sense, we are not generating motor BEMF.

We do get BEMF in the armature in exactly the same way as we get BEMF in an electrically excited generator. The only difference is with an electrically excited generator we have to crank it. Just like an electrically excited generator, with no load, there is no current flowing and little drag. When we draw current we cause drag, but by passing this current through the motor coils too, we cause an increase in torque. This is the self compensating motor/generator This is all standard text book stuff

The magic comes in by making a 90 degree shift in the position of the motor field coil and changing the armature winding.

P.S. and by placing the motor and generator in one case using a single armature.

[shylo]

So the counter force that arises from drawing off a generating coil, actually is causing rotation of the armature?
Which will balance won't it?
Is the counter force equal to the supply? Won't the counter always be less?
Or are they equal? I believe they are equal. Everything balances, that's natures' way.
Delay the counter and we'll have the answer?
A magnet is always attracted to a piece of steel. A field winding is only a magnet ,when power is supplied.
Shut off the field winding , the collapse creates an opposite field , use that for the drive.
Just the way I'm thinking. Probably out in left field. lol
artv