User Manual

3UG4621/3UG4622 current monitoring relays
7.3 Functions
3UG4 / 3RR2 monitoring relays
Manual, 02/2013, NEB927043002000/RS-AA/002
155
7.3 Functions
General functionality
Depending on the set threshold, the 3UG4621 / 3UG4622 current monitoring relays monitor
a single-phase AC load current (RMS value) or DC load current flowing over terminals IN
and M of the device for overshoot (I▲) or undershoot (I▼) or in range monitoring (I▲ and I▼).
The devices differ by their measuring ranges and versions with different rated control supply
voltages. The true root mean square value (tRMS) of the current is measured. Depending on
their design, the current monitoring relays are powered with a rated control supply voltage of
24 V AC/DC or 24 to 240 V AC/DC supply voltage through terminals A1/A2.
The 3UG4621 / 3UG4622 current monitoring relays have a display and are parameterized
with three keys.
You will find the setting ranges and factory settings of the available parameters in Chapter
"Operation (Page 159)."
You will find a descri
ption of the individual parameters in Chapter "
Parameters (Page 351)."
Monitoring
If the rated control supply voltage is switched on and no load current is as yet flowing, the
display indicates 0.0 mA (on the 3UG4621) or 0.00 A (on the 3UG4622) and shows a symbol
for current overshoot monitoring, current undershoot monitoring, or range monitoring.
ON-delay time
If the load current overshoots the lower measuring range limit 3 mA (3UG4621) or 50 mA
(3UG4622), the set ON-delay time begins (onDel). During this time, undershooting or
overshooting of the set threshold values will not result in a relay response of the CO contact.
Tripping delay
If a threshold is reached, the output relay K1 responds after expiry of the tripping delay time
(
I Del
▼
▼
) depending on the set relay switching behavior. An output change-over contact is
available as a signaling contact.
Note
For AC currents I > 10 A, commercially available current transformers, e.g. 4NC, can be
used as accessories. You will find more information in Catalog LV10
(www.siemens.com/lowvoltage/infomaterial
).