# Electric Motor Guru questions



## DavidDymaxion (Dec 1, 2008)

My sepex will spin if you only power the armature. I'd guess it is either acting like a switched reluctance motor (armature poles trying to line up with field poles), or the interpoles provide enough field for the motor to spin, or maybe there is some residual magnetization, or maybe some combination of the three.

In my case it was not induced current in the field, as it was completely disconnected.

Maybe the fine wire is for interpoles and the thicker wire is for field poles?

When the motor runs slower does it also have more torque?

Might the motor actually be a compound wound motor?


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## Qmavam (Aug 17, 2008)

DavidDymaxion said:


> My sepex will spin if you only power the armature. I'd guess it is either acting like a switched reluctance motor (armature poles trying to line up with field poles), or the interpoles provide enough field for the motor to spin, or maybe there is some residual magnetization, or maybe some combination of the three.
> 
> In my case it was not induced current in the field, as it was completely disconnected.
> 
> ...


 I have found that my motor is a compound motor. I was mislead with my ohm meter as it would not resolve a .009 ohm winding in series with a 41 ohm winding. I got further info by energizing the coils and seeing which ones had a magnetic field.
I'll try to get back later, my needs the computer for homework. 
MikeK


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## Qmavam (Aug 17, 2008)

I have now done enough testing that I know now my motor is a short shunt compound motor.
Now I want to know if my motor a cumulative compound or a differential 
compound motor?
Here's a picture showing the polarity of the magnetic fields of the motor 
when I apply current.
http://i395.photobucket.com/albums/pp37/Qmavam/MotorMagneticFields.jpg
The fields are reversed leading me to think the motor is wired as a 
differential compound motor,
and not a cumulative compound motor.
But I have no confidence in that opinion.
Anyone have any ideas?
Any other tests I could do for more info?
This link shows the polarity difference between the two styles.
http://i395.photobucket.com/albums/pp37/Qmavam/CumulativeandDifferentialMotor.jpg
Thanks, Mike


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## major (Apr 4, 2008)

Qmavam said:


> I have now done enough testing that I know now my motor is a short shunt compound motor.
> Now I want to know if my motor a cumulative compound or a differential
> compound motor?
> Here's a picture showing the polarity of the magnetic fields of the motor
> ...


Hi Mike,

It appears you have a compound motor with a 2 plus 2 field. That is 2 series coils and 2 shunt coils on a 4 pole motor. The coils for the series field are 180° apart and so are the shunt coils. This is a common way to wind these motors and still provide a balanced field.

This configuration, as well as all 4 pole machines, will have 2 North and 2 south poles. The 2 N poles are 180° apart as are the 2 S poles. So going around the frame, you have N, S, N, S.

As far as your tests go, you appear to have the armature removed. This does several things. It interrupts the magnetic circuit so you no longer can see the consequent pole reaction. It also interrupts the current path for the series field excitation. So, if you are, as I suspect, applying a voltage to the motor terminals without the armature being present, you get very low series field excitation. This will make the magnetic field difficult to determine on the series coils.

Overall I see nothing you have posted which would lead me to believe it is differential compound. The proper test would be to run it as a motor or as a generator and load it and see if the results match the characteristics for a cumulative compound machine. You can also view the coils, determine the direction of current flow and use the right hand rule to figure the N, S, N, S relationship of the coils.

What was the original application for this motor?

The other thing, I think you said the motor had functioned propelling an EV of some sort. Had it been differential compound, likely it would have burned itself up trying to do that. And what did you use for control?

Regards,

major


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## Qmavam (Aug 17, 2008)

major said:


> Hi Mike,
> 
> It appears you have a compound motor with a 2 plus 2 field. That is 2 series coils and 2 shunt coils on a 4 pole motor. The coils for the series field are 180° apart and so are the shunt coils. This is a common way to wind these motors and still provide a balanced field.


First thanks for your input, I have been using this motor 
for over a year without problem, recently I let the smoke 
out. The motor still runs but seems to have overheated the
shunt coil (oddly only on one end of the motor) I'll get back 
to the motor problem later, let me gleen some information first.
Yes, I think the motor is as you have described.
Here's a picture of the original motor plate, but I think the 
motor has been rewound (different from original) because of
punch marks for proper reassembly.
Some motor spec. 28volt, 65 amp, 2600rpm, 2hp.
http://i395.photobucket.com/albums/pp37/Qmavam/MotorWiringPlate.jpg


> This configuration, as well as all 4 pole machines, will have 2 North and 2 south poles. The 2 N poles are 180° apart as are the 2 S poles. So going around the frame, you have N, S, N, S.


That is what I found as described here;
http://i395.photobucket.com/albums/pp37/Qmavam/MotorMagneticFields.jpg



> As far as your tests go, you appear to have the armature removed. This does several things. It interrupts the magnetic circuit so you no longer can see the consequent pole reaction. It also interrupts the current path for the series field excitation. So, if you are, as I suspect, applying a voltage to the motor terminals without the armature being present, you get very low series field excitation. This will make the magnetic field difficult to determine on the series coils.


Yes I have the armature removed.
I tested the fields like this (same link as above).
http://i395.photobucket.com/albums/pp37/Qmavam/MotorMagneticFields.jpg
I did this test to determine that I had a compound short shunt motor.
http://i395.photobucket.com/albums/pp37/Qmavam/MotorLongShortShuntTest.jpg



> Overall I see nothing you have posted which would lead me to believe it is differential compound. The proper test would be to run it as a motor or as a generator and load it and see if the results match the characteristics for a cumulative compound machine. You can also view the coils, determine the direction of current flow and use the right hand rule to figure the N, S, N, S relationship of the coils.
> 
> What was the original application for this motor?


I was thinking differential because the fields alternated
an the magnetic fields test I performed, but I was not 
at all confident I had that correct.
It was from a military lift, but that is all I was told.



> The other thing, I think you said the motor had functioned propelling an EV of some sort. Had it been differential compound, likely it would have burned itself up trying to do that. And what did you use for control?


I have it powering a gocart for over a year, it has worked 
well, good torque, top speed about 40mph, 
this matches what I calculated using rpm/volt and gear ratio and tire diameter.
I'm using an Altrax NPX 4844 as I recall.
Here's a schematic that is as I originally wired it. I was originally
thinking the shunt had no current flow as wired.
But know as I have 
a new understanding of the motor. I looks like it is being 
PWM by the controller through the brushes and armature.
http://i395.photobucket.com/albums/pp37/Qmavam/Gokartschematicreplacewithproperjpg.jpg
Thanks for your help, MikeK


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## Qmavam (Aug 17, 2008)

Micheal73 said:


> Batteries is big part of electric cars. Electric car is that the batteries will need to be recharged. This will require advanced planning because you'll have to allow adequate time for the batteries to be fully charged.


I'm not sure where your response fits in with my question, but I have a
48 volt battery charger made by Kipoint. It is model KI-0848. I paid $140 for it about two years ago, it was a bid on ebay. I don't know if they still sell on ebay, a quick search didn't find them but I remember them being hard to find when I bought my charger. Here's Kipoint's URL http://kipoint.com.tw/
It is a three stage charger, I have had a new set of deep cycle batteries for over a year and only added distilled water to the batteries once. So I think is doing it's job properly.
The motor in question is on a gokart that we just drive around the neighborhood, we never seem to do any deep discharges, so just parking it on the charger overnight fully charges it.
MikeK


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## JRP3 (Mar 7, 2008)

Qmavam said:


> I'm not sure where your response fits in with my question


Because it's spam nonsense and has been reported.


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