NEMA dimensions are a industry standard for electric motors. The "Z"indicates a non-standard shaft dimension. It could be either the diameter or the length that is not a NEMA standars dimension. A standard 145T motor would have a 7/8" diameter shaft with a lenght of about 2" to 2-1/4". The "C" just indicates that it's a "face mount" motor, meaning the shaft end is machined to bolt diectly to the item being run. Most likely it is a OEM motor made by Delta to speifically fit their saw. Manufacturers quite often have motors and parts manufactured to their specs so that you have no choice but to go back to them to get the right part. That way they make money all the way around.