Source: http://www.hybridcars.com/gm-patents-electric-motor-multiple-magnet-lengths/ Effectively, the tabs will allow the stacks to accept either short or long magnets–the tab will support the shorter magnet halfway down the aperture or get pushed out of the way upon inserting a longer magnet. GM claims there will be at least a 25-percent difference in magnet lengths. What this means is a common motor core whose expensive, permanent magnets can be sized for the vehicle. This increases the commonality of parts to reduce manufacturing costs yet right-size the motor(s) to the vehicle. Bob Wilson
This is just a scheme for them to manage a commonality of parts and associated costs. There are many aspects that affect the cost of a motor. It looks like they are maximizing their cost model for motors across their entire product line requirements. Unfortunately, like most things in life, you have to give something up to get something else. In this case, their motor efficiency will probably not be maximized in all applications, especially regarding power to weight. But, as always, money talks. Most people will knowingly sacrifice some aspects of performance in return for lower prices.
