15 NUMBER OF STARTS
Motors can be started a limited number of times in a defined period without exceeding the permitted winding
temperatur
es. The settings in the Limit Nb Starts protection menu monitors these starts.
Two types of starts are supervised:
● Hot Starts are defined by an initial thermal state greater than 50%
● Cold Starts are defined by an initial thermal state lower than 50%
The maximum allowed number of starts per period is an auto-reset inhibit function. This function monitors the
number of motor starts in the set period. At the end of the period the number of starts is decremented.
Starts are detected using the 52a status from the breaker. Once the number of starts equals the user-defined
setting, the start inhibit is enabled for the set period (inhibit time).
Note:
If User Curve is enabled in the Thermal Overload protection, the thermal state remains at 0% for as long as I
eq
is less than I
th
.
The number of hot starts and cold starts protections should be disabled as they can give an unexpected result.
Example 1
When the maximum number of star
ts in the Supervising Time is reached the Inhib.Start Time is initiated. The
remaining time Supervising Time - tn is greater than the Inhib.Start Time so the start inhibition remains for a
duration equal to Supervising time – tn. Therefore, the inhibition time before a new start is 52 mins with the default
settings and a tn of 8 mins.
Chapter 6 - Current Protection Functions P24xM
158 P24xM-TM-EN-2.1
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