Parker Hannifin S.p.A. Divisione S.B.C. user’s manual TWIN-N and SPD-N
185
whose contacts, are connected to terminals SC-A and SC-B and mechanically driven by relay
mechanics, is open.
This represent the working condition for drive and motor.
When power supply is disconnected from +SR and SR- terminals, switching OFF safety relay,
one of the relay switch cuts OFF power to drive output power stage driving circuits, disabling
output power stage. Under this condition the safety relay feedback switch, whose contacts, are
connected to terminals SC-A and SC-B and mechanically driven by relay mechanics, is
closed.
A dedicated drive parameter (b90.6) shows the safety relay status of each of the two power
output stages (drives) let it to be an available information addressable over fieldbus
communication or standard digital outputs of the converter.
Using this kind of information will increase redundancy level of the safety chain, decreasing
the risk of human and equipment injury.
Attention: both feedback have to be connected within the safety chain of the machine.
This issue must be considered: while switch feedback connected to terminals SC-A and SC-B
is a free potential switch driver directly by safety relay, so its work is independent from drive
firmware; parameter feedback, otherwise, is implemented and used through drive firmware
functions.
The description above is summarized in following table:
safety relay
command
-SR / +SR
Safety relay
feedback switch
status
SC-A / SC-B
Safety relay
firmware feedback
status
b90.6
Safety condition
against unwanted
motor restarts
24V (relay ON) open 1 No
0V (relay OFF) closed 0 Yes
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