Siemens 3UG4 User Manual page 176

3UG4621/3UG4622 current monitoring relays
7.3 Functions
Relay switching behavior
The relay switching behavior can be defined in order to adapt the current monitoring relay to
different external circuit connections and applications.
If the closed-circuit principle (NC) is set, active switching of the relay when no fault is
pending also ensures that a power failure is detected as a fault. If the open-circuit principle
(NO) is set, active switching of the relay only when a fault occurs means that a power failure
is not detected as a fault.
With the setting U
applied but waits to detect the current flow 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 flowing.
With parameterization NC / U
monitoring relay if the output relay K1 switches the contactor coil voltage. However, a defect
that prevents current from flowing 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 flowing
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 flow 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
principle.
You will find the switching states of the output relay below in the section entitled "Function
diagrams" and in Chapter "Diagnostics (Page 180)."
176
= on, the relay switches to the correct state when the supply voltage is
S
= on, a motor can also be switched directly by closing the
S
is applied or after measurement of a current flow on the set NC or NO working
S
3UG4 / 3RR2 monitoring relays
Manual, 05/2016, NEB927043002000/RS-AC/004