WEG SRW 01, User Manual

Page: 35 / 148

Installation and Connection
SRW 01 | 3-7
3
3.7 EXTERNAL CURRENT TRANSFORMER (CT) USE
For applications with higher currents or that are out of the UMC/UMCT model range presented above, it is
possible to use external current transformers (CTs), supplied by the user.
The CTs must have the same specification, being installed separately, one for each motor phase, and have a
suitable ratio for the current range. Additionally, the CT must be specified to be able to supply the VA (burden)
according to the secondary current and cables length. They must be classified as protective CTs in order to
withstand high currents during short intervals without saturating. Normally, they must withstand surges of 20 times
the rated current and present an accuracy ≤ ± 2 %.
The SRW 01 accepts CT secondary currents of 1 or 5 A. The Current Measurement Unit UMC1 or Current/
Voltage Measurement Unit UMCT1 (0.5 - 5 A) must be used in this type of application. If necessary, it is possible
to increase the number of primary turns by passing the CT secondary cables several times through the UMC/
UMCT window, according to the
Figure 3.4 on page 3-5 . The Figure 3.5 on page 3-7 presents a typical wiring
diagram using external CTs.
SRW01 - UMC1
SRW01 - UC
SRW01 - CB
L1 L2 L3
T1 T2 T3
TC3
TC2
TC1
L1 L2 L3
U V W
M
3 ~
I11 I12 I13 I14 I15 I16 IC A1
A2 C1 O1 O2 C3 O3 C4 O4
Figure 3.5: Typical wiring diagram using external CTs
ATTENTION!
The incorrect selection of a current transformer and/or parameterization error at the Control Unit (UC)
will result in an incorrect current calculation, which could cause incorrect indication and possible motor
damages.
ATTENTION!
Change the external current transformer (CT) only with the system powered off.
A CT secondary should never be open circuited while the CT primary circuit is energized.
NOTE!
Some parameters can be changed during the operation. However, there are others that can only be
changed with a stopped motor, according to the quick parameter reference.
3.8 USB CONNECTION
The USB interface is used for monitoring, parameterization and programming of the relay through a PC with the
WLP software.
Basic procedure for data transfer between PC and SRW 01:
1. Install the WLP software in the PC.
2. Connect the PC to the SRW 01 through the USB cable.
3. Switch on the SRW 01 and start the WLP software.