Shorted Scr Checks; Resistance Check - Siemens SIKOSTART 3RW34 Instructions De Service

Troubleshooting
Problem
1. Reversed Winding
2. Dead Ended Winding
3. Dead Ended on All Windings
4. Soft Starter to Fault Contactor Leads
Swapped
5. Switch position SW1-3 does not match
actual circuit type.
L1 L1
T6
T1
T2
T3
T4
L3
L3
T2
T5
L2
Problem 1
Table 16 : Inside Delta Wiring Problems

10.4 Shorted SCR Checks

Perform one of the following checks to identify any shorted SRCs:
These checks require no disassembly of the unit. Extensive SCR tests are detailed in later paragraphs.

10.4.1 Resistance Check

Use an ohmmeter to check for shorted SCR(s) as follows.
1.
2. Measure the resistance from the line to load terminals (L1 to T1, etc.), across each phase of the soft starter.
3. Any reading of less than 3 k
32
Response/Example
The motor runs but makes abnormal sounds and the running current is very high.
The soft starter trips out on a single phase fault. The line with the Dead End Winding will have no
current flow. The other two lines will have very large currents flowing.
Note: Repeated attempts at starting with this connection can damage the soft starter.
The motor does not start. There is no current flow on any of the lines. The soft starter indicators
LED 1 and LED 2 come on at the same time when a RUN command is given.
The motor runs but there is no current limiting during starting. The line and leg currents are
balanced. Due to the phase shift in the leg currents compared with the controller's internal timing
for starting control, there is no current limiting during starting.
Incorrect firing pulses cause very high currents in the motor which can destroy the soft starter.
L1 L1
T6
T2
T4
T3
T5
T1
L3
L3
T5
T2
L2 L2
Problem 2
Hazardous voltage. Will cause death or serious
injury.
Switch off the power before taking the measurements.
High voltage is present on all soft starter components
except heat sinks. All bus bars, terminals, snubber
boards, and SCRs are energized at rated voltage.
Disconnect and lock out all power to unit.
Ω
indicates a shorted SCR that must be replaced. Note that the reading can be as
Ω
high as 3 M .
L1 L1
T1 T6
T4
T3
T3
T4
T2
T6
L3
L3
T5
T2
L2 L2
Problem 3
DANGER
L1 L1
T1
T6 T6
T1
T6
T3 T3
T5
T3 T3
T5 T5
T4
L3 L3
L3 L3
T5 T5
L2
L2 L2
Problem 4
3ZX1012-0RW34-1AN1
L1 L1
T1 T1
T1 T1
T6
T4 T4
T2 T2
T4 T4
T2 T2
L2 L2