SINUS PENTA
PENTA MARINE
IRIS BLUE
STO FUNCTION
APPLICATION MANUAL
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4. DIAGNOSTICS
The STO function is based on a double channel with diagnostic (1oo2 in the IEC 61508-6 nomenclature)
hardware architecture. This means that diagnostic tests are required to validate the STO function and to
periodically verify the hardware integrity.
The two diagnostic tests, working at different levels and with different timing, are based on consistency
check logics and three indicator LEDs.
The two diagnostic tests are the following:
DT01 Periodic proof-test (related to
“System OK” L8 and L9 LEDs)
DT02 Periodic proof-test (related to
“PWM Enable” L2 LED)
As specified in the following descriptions, the simple and easy diagnostic test DT01-DT02 has to be
performed by the User at an interval time lower than or equal to one year.
To do that it is needed to remove, if present, the display/keypad from the front of the drive and to verify the
status of the diagnostic LEDs from the transparent window.
The diagnostic test requires the individual energization and de-energization of the two ENABLE-A and
ENABLE-B commands. Therefore, the drive application circuit shall allow for this operation. The easiest
way to do this is to provide switches or pushbuttons, preferably operable only by service people, applied in
series to the two ENABLE-A and ENABLE-B wires.
Another continuous coherency check is performed by the board CPU under firmware control. This is an
additional verification of the STO related signals, and the result, if failing, is reported as alarm A140. When
the alarm trips, the drive operation is locked. This test is independent of the drive status and does not
require any operation by the user. Alarm A140 is detailed in section 6.5 Alarm Messages Generated by
the Drive.
DT01 Periodic proof-test (Diagnostic LED
s “System OK” L8 and L9)
Based on hardware components only.
Performed with a specified sequence of 4 steps.
Checked by visual inspection of Diagnostic LED
s “System OK” L8 and L9.
Proof-test Interval: one year.
NOTE
This proof-test circuit is integrated into ES927 board to prevent the presence
of dormant failures.
A hardware proof-test circuit based on redundant logic gates has been implemented on ES927 and the
periodic proof-test is activated by an external command. The check is performed with the activation of the
STO function (by activation of external components for de-energization of at least one of the STO input
signals).
The diagnostic circuit reads the command signals status present in the two channels of STO function
circuit and, when the test is ac
tive, its combinational logic gives “true” only if all the command signals in
both channels are correct. In this case, both the Diagnostic LED
s “System OK” L8 and L9 are ON.
In particular, when the STO function is activated, the proof-test hardware circuit checks the congruence of
all the PWM signal across the logic output buffers, and it is able to detect failures associated with those
components.
