4.7 Safety Function
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4
Operation
4.7
Safety Function
The safety function is incorporated in the SERVOPACK to reduce the risk associated with the machine by pro-
tecting workers from injury and by securing safe machine operation. Especially when working in hazardous
areas inside the safeguard, as for machine maintenance, it can be used to avoid adverse machine movement.
4.7.1
Hard Wire Base Block (HWBB) Function
The hard wire base block function (hereinafter referred to as HWBB function) is a safety function designed to
shut off the motor current by using the hard wired circuits: Each circuit for two channel input signals blocks
the run signal to turn off the power module, and the motor current is shut off. (Refer to the diagram below.)
Note: For safety function signal connections, the input signal is the 0V common and the output signal is the source output.
This is opposite to other signals described in this manual. To avoid confusion, the ON and OFF status of signals for
safety functions are defined as follows:
ON: The state in which the relay contacts are closed or the transistor is ON and current flows into the signal line.
OFF: The state in which the relay contacts are open or the transistor is OFF and no current flows into the signal
line.
(1) Risk Assessment
Perform risk assessment for the system and confirm that the safety requirements with the following standards
are fulfilled before using the HWBB function.
EN954-1 Category3
IEC61508-1 to 4 SIL2
The following risks can be estimated even if the HWBB function is used. These risks must be included in the
risk assessment.
• The motor will move in an application where external force is applied to the motor (for example, gravity on
the vertical axis). Take measures to secure the motor, such as installing a mechanical brake.
• The motor may move within the electric angle of 180 degrees in case of the power module failure, etc. Make
sure to take the proper measures to ensure safety when the motor starts to move. The number of travel dis-
tance depends on the motor type as shown below.
Rotational servomotor: 1/6 rotation max. (rotation angle at the motor shaft)
Direct-drive motor:1/20 rotation max. (rotation angle at the motor shaft)
Linear servomotor: 30 mm max.
• The HWBB function does not shut off the power to the SERVOPACK or electrically isolate it. Take mea-
sures to shut off the power to the SERVOPACK when performing maintenance on it, etc.
6
5
/HWBB2+
/HWBB2-
4
3
CN8
/HWBB1+
/HWBB1-
0 V
Control circuit
SERVOPACK
Switch
Block
Block
Power module
Power supply
24-V power supply
Fuse
Linear
servomotor
Run signal
