Rockwell Automation Publication 440R-UM014D-EN-P - December 2019
27
Status Indicators and Diagnostics
Chapter 6
• Voltage-Free Contactor
The MSR55P safety relay detects line breakage on L1, L2, and L3. The
ERR semiconductor output turns ON and the ERR indicator flashes the
appropriate number of times. The machine-controlled system continues
to control the motor. This state is considered a safe situation because the
outputs of the MSR55P safety relay are de-energized. The machine
control system can respond to the ERR output and turn off the motor.
When the contactor turns off, and the motor spins to a standstill; the
line breakage is detected and the following occurs:
– The outputs of the MSR55P safety relay remain de-energized.
– The ERR output turns ON.
– The ERR status indicator flashes the code that is associated with the
breakage.
Simultaneity of Measuring
Signals
As an additional safety feature, the two input signals (L2 and L3) are compared
continuously. This feature allows the MSR55P safety relay to detect internal
failures in one measuring signal.
If the signals are different for at least 2.5 s (one channel >V
m
, the other <V
m
), a
simultaneity failure is detected. The semiconductor output ERR is switched
on, the ERR status indicator flashes with failure code 5, and the OUT
indicator is off.
If the measured signals return to the same level <V
m
, the error remains stored
and the outputs are disabled.
The simultaneity failure is only reset when both channels return to >V
m
. If
after that both channels drop below the setting value, <V
m
, the output relays
switch on.
Potentiometer Error
To achieve the required safety when adjusting the voltage threshold for
standstill detection, each setting function is accomplished with two
potentiometers having one common setting knob. If another setting is detected
on the two corresponding potentiometers, the potentiometer error V
m
or t
s
is
displayed.
To correct the fault, try to readjust the potentiometer. Make sure that you feel
the detent.
