Frequency of starts

The frequency of starts for pumps refers to the number of times the electric motors that power them start up per hour. The permissible frequency of starts depends on the motors used and their power, rotational speed, and type. See Fig. 1 Frequency of starts

Start-ups lead to the build-up of heat in electric motors and flexible couplings and cause the contactors to wear prematurely, which limits the permissible frequency of starts. Exact information about the number of hourly start-ups permitted should be obtained from the motor's supplier with respect to operating conditions.