Ex: An induction motor 2000 kW, 6.3 kV, 225 A, Ins. Class F with Class B rise, Rated ambient = 40 Deg C.
Cold Starts( 03 Attempts):
If the motor is at standstill, or the motor was running less than its rated load 225 A at 40 Deg C ambient, then the motor was NOT running at rated load. That means still the motor is at so called “COLD” state. Then if you are going to stop that motor and restart, then you are allowed to attempt 3 starts consecutively (one after the other) on that motor.
Hot Starts( 02 Attempts):
If the motor was running at its full load 225 A at 40 Deg C ambient and after a while when it establishes its steady state temperature, then the motor was supposed to be running at its rated conditions. That means the motor is now in its “HOT” state. Then if you are going to stop that motor and restart, then you are allowed to attempt only 2 starts consecutively (one after the other) on that motor.
“How we determine that which condition is cold start condition…. “
From my experience, it is totally dependent on the user of the motor. To decide whether the motor is at cold or hot state, you have to analyse the load in Amps, motor steady state body temp, ambient temp etc. By simply measuring the body temp and allowing a margin for the hottest point depending on the insulation class, you can decide whether the motor has reached its rated temp even at a reduced load. In any case, if the motor has attained its rated temp depending on the class of insulation, then that motor has reached its rated condition ( may be due to high ambient, bearing friction etc ) even though the load in Amps is lower than the rated 225 A. Therefore the temp is the guide.
“…after we start the 1st time and then stop immediately .Afterthat we start again ,is this condition in second successive cold start ?”
Yes it is still a cold start since you have NOT allowed the motor to reach to its steady state temperature.