Publication 440R-UM004A-EN-P - December 2008
19
Safety Concept
Chapter
1
Output Pulse Test Considerations
If the pulse testing of
any
safety output is disabled, the maximum
safety rating will be up to and including SIL CL2, PL(d), and CAT 3 for
any safety chain incorporating
any input or output
of the MSR57P relay.
You may need to disable pulse-testing if the connected device does
not support OSSD inputs. Refer to the product documentation for your
connected device.
Considerations for Single-encoder Applications
When configured correctly, the MSR57P relay performs these
diagnostics on the encoder:
•
Sin
2
+ Cos
2
diagnostic.
•
detection of open or short-circuit.
•
encoder supply voltage monitoring.
•
detection of illegal quadrature transitions of the sine and cosine
signals.
A safety rating up to and including SIL CL3, PL(e), and CAT 4 can be
achieved in a single-encoder application with these requirements:
•
The motor is a permanent magnet (PM) brushless AC motor.
•
The motor controller must be configured as a closed-loop
application with field-oriented control using the single-encoder
for commutation.
•
The motor-to-encoder coupling is designed to exclude shaft
slippage as a dangerous failure mechanism.
•
The MSR57P relay is configured for Sin/Cos encoder type.
IMPORTANT
Setting any of the P71 [MP_Out Mode], P72 [SS_Out Mode],
P73 [SLS_Out Mode], or P74 [DC_Out Mode] parameters to 1 =
No Pulse Test disables internal diagnostics as well as external
diagnostics required to achieve higher safety ratings.
You must exercise the SS_In input at least once every six
months.
