Rockwell Automation Allen-Bradley Guardmaster 440R-S35011, User Manual, Page: 36 / 50

36 Rockwell Automation Publication 440R-UM014D-EN-P - December 2019
Chapter 8 Troubleshooting
ERR Indicator Flashes One
Time (Step 2)
Reset of an undervoltage event occurs automatically; regardless of the status of
the fault reset input at terminal X3.
Two cases must be considered:
• Momentary
The MSR55P safety relay resets itself automatically if a momentary
undervoltage event occurs, regardless of the fault reset circuit. The
momentary power dip can occur in the two cases:
– Output energized (standstill state): The output de-energizes
momentarily and the ERR semiconductor output turns ON. When
the voltage returns to the normal level, the output is re-energized and
the ERR semiconductor output turns OFF.
– Output de-energized (non-standstill state): With the motor rotating
faster than standstill, the outputs are already de-energized. When the
voltage drops, the ERR indicator flashes 1x and the ERR
semiconductor output turns ON. When the voltage returns to
normal, the ERR indicator stops flashing and the ERR
semiconductor output turns OFF.
If the ERR semiconductor output is an input to the PLC that stops the
process if there is an error with the MSR55P safety relay, a momentary
voltage dip is difficult to trace to its cause.
• Sustained
The ERR semiconductor output is ON and the ERR indicator is
flashing 1X. An undervoltage exists at A1/A2. Measure the voltage at
the terminal A1 to A2 as shown in Figure 20 on page 35 . With your
schematics, trace the voltage back to its source to determine what could
be the cause of the undervoltage.
Wire Break at L1, L2, or L3
(Step 3)
Wire breakage is hierarchical. If both L2 and L3 are broken, then the MSR55P
safety relay reports that L2 is broken. If L1 is broken, the MSR55P safety relay
reports that L2 is broken as L2 has a higher priority than L3. When L2 is
corrected, then the MSR55P safety relay reports the L3 broken.
Turn off the motor and allow it to achieve standstill.
Use an ohmmeter to measure the resistance of the motor windings at L2 or L3
to L1, as shown in Figure 21 .
• OK - a low resistance
• Not good - the meter shows an open circuit,
ATTENTION: Use an appropriate resistor network to discharge residual
capacitance, if any.