The 2 main reasons why MPRs provide detailed protection curves is because of
1) custom or unusual motor designs for specific purposes, which gets more and more prevalent as HP size goes above NEMA frames (loosely over 250HP), and
2) when you need to push your motor application right to the ragged edge but for economic or technical reasons, you don't want to just buy a bigger motor.
If that seems to fit your situation, you have no viable choice but to contact the motor mfr or have an Engineer do a very detailed motor analysis. As mentioned, software programs like SKM and ETAP are tools the EE will use, but they still rely upon knowing something about the thermal damage curve of the motor, and that is very difficult to determine on an existing motor with no mfrs data. The built-in starting curves in those software programs are mostly what I describe below (they are available everywhere) but these high end software companies also amass some typical values by soliciting curve data from various installations submitted by users, so that can be helpful too if you don't know much about your motor. SKM and ETAP are very expensive programs, not usually justifiable for the one-off user, typically around $5-7k (plus training). Its usually far less expensive to just hire an experienced EE that has the software already. If however one of those two reasons don't seem to fit your situation, read on.
Generally there are standards set by NEMA for North American design motors and IEC for elsewhere and they establish curve "classes", NEMA & IEC classes are pretty much the same. They are all based upon the thermal damage curve that will be associated with a trip time at 600% current because that is the accepted average Locked Rotor Current of a Design B motor, which makes up 95% of AC industrial motors used. So Class 10 means it will trip in 10 seconds at 600% FLC, Class 20 in 20 seconds, Class 30 in 30 seconds etc. These cover the thermal damage curves of 95% of AC motors out there. Class 30 is rare, what we used to call "Mill Duty" motors and you will know one when you see one, they are often twice as big as you would expect. Most NEMA frame motors are going to be designed around Class 20, most IEC motors are designed around Class 10. ESPs (Electric Submersible Pumps) are also usually Class 10 (but some are Class 5 because they know they are in warm or hot environments, like oil pumps, so be careful with those). If you select a Class 10 curve, you are generally very safe in protecting your motor even though you may not be utilizing its full capability. But if you are not experiencing nuisance tripping, then there is no down side to using Class 10 as a default position.
