Winding Universal Motors?

[smitty1322]

I was told that when designing a wind for a universal motor, the ratio between the number of turns in the armature and the number of turns in the field should ideally be 2:1. However, when asking for the theory behind this, the only response I got was that this is the way it has always been. Is there, in fact, an ideal ratio of turns?

 

[smitty1322]

I assume due to the lack of responses that I should clarify my question a bit more. I have a "universal" motor which has a field(stator) and armature (rotor). Now, in a PM DC motor the wind can be change to get a new performance by using a linear relationship. Well at least this will get you close. However, I have changed the wind (# of turns & wire gauge) on my "universal" motors and can't seem to find the relationship.
For example, to change a blender motor from 24K RPM's to 30K rpms I used the PM relationships and reduced the number of turns in my armature. I then used the 2:1 ratio I asked about before to get the turns in the field. What should have changed my speed by 6k only changed 3K. However, I can put all three armatures into the motor with the new field, each armature with less turns than the one before, and get the same speed? Can anyone recommend some books on the design of these motors? Something like "Design handbook for PM motors and tachometer" by Robert Perrine SR.? I found this book very helpful but it is only for PM motors?

 

[jbartos]

Suggestion: Contact
1.

http://www.ieee.org

or
2.

http://www.iee.org

for more information on universal electric motors in form of papers published in their periodicals. They may also have some information about published books, proceedings, simposia records, conference records, etc., by them.

 

[teco]

smitty:-
theres a book called "small motors and transformers design and construction" edited by E.MOLLOY.its old but good. it exsplains and provides all the calculations to build small ac/dc commutator motors.
good luck
kind regds.