Rated operational current I
e
The rated operational current I
e
is the current that can be continuously conducted by the feeder
(switchgear and motor). Normally this is the rated current I
e
of the motor. The setting range
depends on the rating class of the 3RW55 or 3RW55 Failsafe soft starter.
Note
Electronic motor overload protection
The electronic motor overload protection (Page 166) can be switched off. In this case, motor
overload protection must be ensured by means of a temperature sensor (Page 169) in the motor
(thermistor motor protection with temperature sensor).
Service factor
Three-phase motors have a service factor that is stated relative to the rated power of the motor.
The service factor determines the maximum permissible overload factor of the motor in the
ramped-up status. A service factor of, for example, 1.15 means that you can operate the motor
up to 1.15 times the rated power without damaging it permanently.
To be able to use these higher motor power ratings, you must set the parameter "Service factor"
on the 3RW55 or 3RW55 Failsafe soft starter so that the motor overload protection is triggered
after an appropriate delay. If a service factor has been specified by the manufacturer, set this
service factor. If no service factor is specified, set service factor 1.0 (factory setting).
Note the different trip characteristics for a service factor ≤ 1.05 and > 1.05 in the Internet (
support.industry.siemens.com/cs/ww/en/ps/25099/char
Setting range
Factory setting
Increment
1.0 ... 1.15
1.0
0.01
Rated torque
If the motor's rated torque is not indicated on the rating plate, you can calculate it using the
following formula:
Rated torque (Nm) = Power (kW) × (9 550 / rated operating speed (rpm))
For the setting "0 Nm" (factory setting), the 3RW55 and 3RW55 Failsafe soft starters calculate the
required value automatically.
Setting range
Factory setting
Increment
0 ... 10 000 Nm
0 Nm
1 Nm
Rated operating speed
The rated operating speed is required for calculating the current rated torque.
Setting range
Factory setting
Increment
500 ... 3 600 rpm
1 500 rpm
1 rpm
Parameter assignment
6.5 Motor parameters
SIRIUS 3RW55 and 3RW55 Failsafe Soft Starters
96
Equipment Manual, 02/2022, A5E35630887002A/RS-AF/006