I went looking and here is some of what I found. Hopefully it will help you a bit.
Numbers Of Rotor/Stator Slots For Reliance Electric 180-440T TEFC Motors:
http://www.reliance.com/mtr/pcrssmn.htm
From:
http://maintenanceforums.com/eve/forums/a/tpc/f/7161085912/m/8621030173
There are a number of rough thumbrules used in motor design, but they won't get you very far since one manufacturer may build a motor differently than another manufacturer even when the specs are the same.
Stator slots will usually be a multiple of 6. The exception may be slow speed motors which may be a fractional slot configuration.
Generally speaking, as the torque rating (horsepower/speed) goes up, the number of stator slots goes up.
For a given number of stator slots N1, there are general restrictions on number of rotor slots N2:
The following general "thumbrules" are taken from Electrical Apparatus Magazine June 2005 "The importance of Slot Combination on Motor Design" by R. Nailen:
|N1-N2| < > P +/- 2 where P is number of poles
|N1-N2| < > 3 * m * P where p is integer
|N1-N2| < > 5 * P
N2 should be above or below N1 by at least 15 bars or 25% of N1.
N2 is generally not odd
N2 should not be twice a prime number
N2 should not be divisible by the number of poles
Some designers prefer N1 > N2 although there are lots of exceptions
N1/N2 = 24/19 is a relatively common ratio
Again, there are very few guarantees of what we can predict just based on the horsepower, speed etc. Your best bet is having a count or access to a list or info from the manufacturer.
• Skew is an angular twist of a slot away from the axial direction.
• Typical skew is one stator slot pitch.
• The purpose of the skew is to reduce spatial harmonics in the air-gap flux that are
introduced by a finite number of slots and the slotting combination.
Typical results of skewing are as follows:
• Reduction of induced EMF in bar, improved voltage waveform
• Higher rotor leakage reactance and less torque
• Skewed bars have a current that has a circumferential component which develops
a small axial force which imposes additional load on bearings
• Nonuniform air gap flux increases core and stray losses
• Improved speed-torque characteristics, including elimination of locking torque at
zero speed and cusps at various speeds
• Reduced likehood of electrical noise problems
