6-22
Safe Torque Off
890CS Common Bus Supply - Frames B & D; 890CD Common Bus Drive and 890SD Standalone Drive - Frames E & F
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The 890 STO feature does not provide or guarantee any galvanic isolation in accordance with EN 60204-1
Section 5.5. This means that the entire system must be isolated from the mains power supply with a
suitable electrical isolation device before any drive or motor maintenance or replacement procedures are
attempted. Note that even after the power has been isolated, dangerous electrical voltages may still be
present in the 890 drive. Safe discharge times and details are specified elsewhere in this manual.
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The STO function must not be used for electrical isolation of the 890 drive and power. Whenever any
personnel require to work on the drive, associated motor or other power items, they must always use
recognised and suitable electrical isolation devices and lock-off procedures as appropriate.
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Terminal X11/02 or X11/04 must be connected to earth at one common point in the drive system. For
multi-drive systems this can be a shared earth point.
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The STO user output, serial communications or MMI messages relating to accessing or viewing any safety
monitoring statuses are for information only and should not be relied on. They are not part of the drive
module safety system and its associated PL/SIL declared rating. Any customer use of these must be
appropriately risk assessed by the customer in accordance with any relevant standards or regulations.
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The STO safety function must be tested regularly. The frequency should be determined by the machinery
builder. An initial frequency of once per week is suggested.
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When using an external safety control unit with adjustable time delay, for example when implementing an
SS1 function, the time delay must be protected to prevent unauthorized adjustment. The adjustable time
delay on the safety control unit must be set to a value greater than the duration of the braking ramp
controlled by the 890 with maximum load inertia and from maximum speed. Any external forces must also
be considered, e.g. effects due to gravity.
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When implementing a SS1 function with the 890, the user is responsible for ensuring the drive’s
configuration will allow a controlled braking ramp to be initiated by the external safety device. This is
particularly important when using serial link communications for normal control of the drive.
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During the active braking phase of SS1 or Stop category 1 (controlled stop with safely monitored time
delay according to EN60204-1), faulty operation of the drive must be allowed for. If a fault in the drive