Siemens SIRIUS 3UG4 - Page 124

With the setting U
S
= on, the relay switches to the correct state when the supply voltage is applied
but waits to detect the current 󹪞ow before actually monitoring. The monitoring relay is thus
switched on without generating an error message because, for example. the motor is not yet
running and no current is 󹪞owing.
With parameterization NC / U
S
= on, a motor can also be switched directly by closing the
monitoring relay if the output relay K1 switches the contactor coil voltage. However, a defect
that prevents current from 󹪞owing is not signaled with this setting. In this case, setting the relay
switching behavior to NC / I > 3 mA (3UG4621) or NC / I > 50 mA (3UG4622) is appropriate. When
the supply voltage is applied, the output relay K1 is switched to the operate condition and the
ON-delay time (onDel) is started. If current is not yet 󹪞owing normally after this time has
elapsed, the output relay will switch back to the fault condition.
If a motor is not to be started directly using the monitoring relay, but in parallel using a
pushbutton, with the monitoring relay ensuring the contactor holding, the switching behavior
can be set accordingly.
With the setting I > 3 mA (3UG4621) or I > 50 mA (3UG4622) in combination with a set ON-delay
time onDel = 0, output relay K1 will only switch to the OK condition if a current is actually
measured. In this case, the monitoring relay will hold the contactor until a fault occurs or the
current 󹪞ow is interrupted by a further button or switch. If an ON-delay time is necessary, initial
switching of the output relay on application of the supply voltage or on starting the ON-delay
time must be suppressed by means of external logic.
Note
The name of the parameter values is based on the assumption that the ON-delay time onDel = 0
is set. The output relay K1 then responds either immediately when the supply voltage U
S
is
applied or after measurement of a current 󹪞ow on the set NC or NO working principle.
You will 󹪝nd the switching states of the output relay below in the section entitled "Function
diagrams" and in Chapter "Diagnostics (Page 129)."
3UG4621/3UG4622 current monitoring relays
7.3 Functions
SIRIUS 3UG4 / 3RR2 monitoring relay
124 Equipment Manual, 07/2021, NEB927043002000/RS-AD/005