Under stable signal time, short pulses, which could lead to safety functions being incorrectly activated, can be filtered.
NOTICE
The stable signal time extends the safety option response time. The safety option only activates the safety function after the
response time has expired.
If the signal to the input on safety option is not stable, the option responds with a fault.
Definition of a Stable Signal
Following a change to the DI input signals, the option triggers an internal monitoring time. Use parameter 42-23 Stable Signal Time to
select an appropriate stable signal time. A constant signal level is a high or a low state, at least for the time specified in parameter 42-23
Stable Signal Time.
Safety function
Active
Inactive
S table signal time S table signal time
Illustration 16: Filter for Suppressing Temporary Signal Changes
3.6.8 Zero Speed Timer Error Detection
Zero Speed Timer monitors if the drive operates below 120 RPM during Safely Limited Speed.
Parameter 42-18 Zero Speed Timer contains the remaining time until the monitoring responds. The safety option signals Alarm Ext Fail
Prec Thresh Timer Elapsed after the monitoring time expires. Define the monitoring time while commissioning the system depending on
the particular application.
3.6.9 Yearly Test
According to EN ISO 13849-1, EN IEC 62061, and EN IEC 61508, the safety option must regularly test its safety-relevant circuits to ensure
correct functioning. This test must be performed at least once every year. After the power supply has been connected, the safety
option checks its circuits to switch off the torque each time the STO function is selected. The safety option monitors the regular test
interval of its safety-relevant circuits using a time module.
Functions and Systems Overview
Installation Guide | VLT® Safety Option MCB 150/151
AQ279747441421en-000101 / 130R0292
34 | Danfoss A/S © 2018.09
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