Does motor starts number affect motor life?

The numerical number of starts that we are talking about is a statistical figure coming out of the expert programs. More failures are caused by manufacturing defects. Why should a motor be restarted, if the process does not require it. If the process needs it, and stated in the specification, the designer knows the tricks to work out CMR for that applications. The second largest source would be the supply. During installation, more number of starts are taken for tune up. But if your supply system is weak the number of starts needed increase due to tripping. This will vary country wise, say in India we can expect frequent starting as compared to places like Europe.

Over-sizing the machine as an alternative. It did not work in my motors as the design had brazed rotors. Rotor losses will increase due to over-sizing and heat accumulated faster than the reduction in the starting time. This is bad during commissioning when frequent successive starts are taken. The heat generated in the rotor is normally the limiting factor. Variable speed drive is a good solution, but not economical in many cases.