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Limits for repetitive induction motor DOL starting
Motor Starting
The following link gives NEMA MG-10 recommendations regarding maximum starting frequency and required off time between starts as a function of motor horsepower, speed, and load inertia which apply for NEMA frame motors (typically 250hp or less). These are repetitive starting limits targeted toward chronic long-term use.
https://www.efficientplantmag.com/2015/05/safe-starting-of-motors-check-for-temperature-increase/
These limits do not extend to the range of large motors. For those motors, additional info is needed from OEM to evaluate repetitive starting duty.
There may be other less restrictive limits for acute repetitive starting such as 2 successive starts allowed if motor was initially cold as allowed per NEMA. Long term repetitive starting are different than infrequent acute limits, however applying the limits / times for long term to evaluate acute duty would be conservative and may be the best option when there are no other allowances accessible.
https://www.efficientplantmag.com/2015/05/safe-starting-of-motors-check-for-temperature-increase/
These limits do not extend to the range of large motors. For those motors, additional info is needed from OEM to evaluate repetitive starting duty.
There may be other less restrictive limits for acute repetitive starting such as 2 successive starts allowed if motor was initially cold as allowed per NEMA. Long term repetitive starting are different than infrequent acute limits, however applying the limits / times for long term to evaluate acute duty would be conservative and may be the best option when there are no other allowances accessible.