Inside Delta Wiring Problems - Siemens SIKOSTART 3RW34 Instructions De Service

Fault
Soft starter is off but motor is
running
Motor overload relay
trips during starting
Motor not able to accelerate
load
Motor branch circuit protection
trips during starting or running
Table 15 : (cont.) Troubleshooting

10.3 Inside Delta Wiring Problems

When the switch is set to "In Line", the motor must be operated in In Line
connection and when the switch is set to "Inside Delta", the motor must be
operated in Inside Delta connection!
Setting the switch to the wrong type of connection can cause very high currents
during operation. These currents can destroy or damage the SCRs and other
components. Be sure to set the soft starter only to the type of connection actually
used.
Fig. 23 shows a correct inside delta connection. With the correct connection, the motor runs properly with current
limit during starting and the line and leg currents are balanced.
Table 16 lists four improper connection problems and the unsuccessful response for each. The "Example" column
illustrates only one of many combinations that may be responsible for the problem.
L1
L3
L2
Fig. 23 : Proper Inside Delta Wiring Connection
3ZX1012-0RW34-1AN1
Cause Check/Remedy
Unsuitable delta motor A certain delta motor design (wired Inside Delta) will not start softly with a high
friction load (e.g., conveyor), only with a low friction load (e.g., water pump). The
soft start produces balanced three-phase power to the motor, but it becomes
stuck at a low rpm until the end of the start ramp at high current. It then jumps
quickly to full speed due to the high voltage and current.
Shorted SCRs Check voltage from terminal A1 to A2 to verify that RUN coil is not energized.
(LED 2 double flashing) Check SCRs as described in Section 10.4.
Motor is overloaded while Check for a mechanical cause of overload and clear.
running
Check that motor comes up to speed when started by applying across-the-line
full voltage directly to the motor. An alternative is to use the soft starter with T1
set at 0 (0.5 seconds) and U at F (80% full voltage).
a) If motor cannot accelerate the load, increase motor size; for correct soft starter
selection, refer to Section 4.
b) If motor accelerates the load, continue checking the following causes.
Improper overload relay Check overload relay to determine correct settings.
Overload relay current Verify current transformer wiring per applicable diagram(s).
transformers incorrectly
wired
Branch circuit protective Size the device in accordance with all applicable standards (DIN/IEC).
device incorrectly sized
Check circuit breaker trip settings.
Incorrect power wiring Check all power wiring connections to determine if a phase-to-phase or
causing a short on input or phase-to-ground short is present.
load side of soft starter
WARNING
L1
T6
T1
Motor
w3
w1
SIKOSTART
T3
L3
T5 w2 T2
T4
L2
Troubleshooting
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