System Features
3.6 Residual risk
Safety Integrated
Function Manual, 05/2010, A5E03264275A
51
3.6 Residual risk
The fault analysis enables the machine manufacturer to determine the residual risk at his
machine with regard to the drive unit. The following residual risks are known:
WARNING
Due to the intrinsic potential of hardware faults, electrical systems are subject to additional
residual risk, which can be expressed by means of the PFH value.
WARNING
• Faults in the absolute track (C-D track), cyclicly swapped phases of the motor
connections (V-W-U instead of U-V-W) and reversal of the control direction may cause
acceleration of the drive. Due to the fault, however, Category 1 and 2 stop functions to
EN 60204-1 (fault response functions STOP B to D in accordance with Safety
Integrated) are not activated.
Stop function Category 0 to EN 60204-1 (fault response function STOP A in accordance
with Safety Integrated) is not triggered until after the transition or delay time set in the
parameter has elapsed. These faults are detected when SBR is selected (fault reaction
functions STOP B/C) and stop function category 0 to EN 60204-1 (fault reaction function
STOP A in accordance with Safety Integrated) is triggered as early as possible
regardless of this delay. Electrical faults (defective components or similar) can also
cause the response cited above.
• Simultaneous failure of two power transistors (one in the upper and the other offset in
the lower inverter bridge) in the inverter may cause brief movement of the drive,
depending on the number of poles of the motor.
Maximum value of this movement:
Synchronous rotary motors: Max. movement = 180 ° / no. of pole pairs
Synchronous linear motors: max. movement = pole width
WARNING
• Upper limit violations may briefly lead to a rotational speed higher than the speed
setpoint, or the axis may overtravel the defined position to a certain extent, depending
on the dynamic response of the drive and on parameter settings.
• Mechanical forces greater than the maximum drive torque may force a drive currently
operated in position control mode out of the Safe Operating Stop state (SOS) and
trigger stop function category 1 to EN 60204-1 (fault reaction function STOP B).
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