Motor Starts and motor life

I am familiar with one operation using salt water resistance for starting large AC Synchronous motors. Resistance varied by distance between electrodes. This is a large wind tunnel with about 5 x 30,000 hp motors and the water resistance enables balancing load between motors during starting. It is a complex system and very stressful to operators as well as motors since control of max current is critical but so is heating of motors at low speed. Naturally this is a very old system and that is another factor making the operation difficult. Maintaining the chemistry of the fluid is a major factor in operation.

There is a table in the NEMA MG-10 publication summarizing the max number of starts per hour and minimum time between starts for NEMA A & B class motors under "normal" starting conditions. I believe they define normal as full load, line voltage starts.

In general, the bigger the motor and the faster the nameplate speed, the fewer starts/hour and the more time required between starts. This is based on motor overheating.

For example, a 100 HP, 2 pole motor is allowed 2.6 starts/hour with a minimum of 220 seconds between starts. A 200 HP 2 pole motor is allowed 2 starts/hour with 600 seconds between starts.

There is a question that must first be answered:
What size of motor is this?
The response to "how many starts per hour" is vastly different.
Consider the motor in your ink-jet printer.
On the opposite end: a 10,000 kW compressor driver.

The first could start once every couple of seconds.
I certainly wouldn't expect to start the last one 20 times an hour.

API considers 2 starts in succession from cold condition (based on the rotor and stator being at ambient temperature) or 1 hot start (with the rotor and stator being at full load, running temperature). After the second of a two start attempt, it could well be 6 or 8 hours before the one hot attempt could be made.

Don't forget that the answers also change if a variable frequency drive or soft starter is being used.