Siemens 7SR105 Rho - Thermal Protection: Start Protection (48, 66); Figure 3-5 Number of Starts Protection (66)

7SR105 Rho Description of Operation
©2018 Siemens Protection Devices Chapter 1 Page 28 of 57
3.1.3 Thermal Protection: Start Protection (48, 66)
A motor start is detected as described in section 3.1.
3.1.3.1 Number of Starts (66)
This feature is used where plant or motor operational constraints are to be considered or to ensure that permitted
winding temperatures are not exceeded.
Gn 66 Max. Number of Starts setting allows the user to select the maximum permissible number of starts
Once the maximum permissible number of starts has occurred within the defined period then starting is
inhibited for the duration of the start inhibit delay setting.
Gn 66 Max. Starts Period setting is the minimum time interval within which the assigned number of starts
may occur (e.g. starts per hour for a notching or jogging device.
Gn 66 Start Inhibit Delay setting: Where the number of starts has been exceeded within the ‘max starts
period’ starting is inhibited until this time delay has elapsed.
Gn 66 Time Between Starts setting is provided to determine the minimum permissible time between two
consecutive starts.
Gn 66 Restore After Power Down setting: Where enabled the number of motor starts recorded to the
relay powering down is restored when the relay is powered up again.
A restart is inhibited by the same output contact used for the thermal restart inhibit feature. The restart inhibit
output is only energised after the motor has stopped (current falls below I
STOP
) so that the start sequence in
progress is not interrupted.
A ‘Start Protection Reset’ command is available in the ‘Maintenance Menu’ which allows the user to reset both the
Number of Starts and the Minimum Time Between Starts features.
IA
IB
IC
PPS/
NPS
Filter
I
EQ
Gn 49 NPS Weighting Factor
Gn 49 NPS Weighting
Motor Running
No Accel
Gn 49 Itheta Thermal OL
Gn 49 Motor Start Type
Gn 49 Motor Start Current
Gn 49 End of Start Type
Gn 49 End of Start
Gn 49 Motor Stop Type
Gn 49 Motor Stop Current
Stopped
Run
Start
Enabled
Gn 66 Number of
Starts
En
Gn 66 Max. No. Starts
Gn 66 Max Starts Period
Enabled
Gn 66 Time
Between Starts
En
Gn 66 Time Between Starts
Gn 66 Start Inhibit
Delay
≥
1
Restart Inhibit
66 Starts Exceeded
66 Fail to Run
Motor start to motor stopped determined
Figure 3-5 Number of Starts Protection (66)