Safety Function; Hard Wire Base Block (Hwbb) Function - YASKAWA E-V Series User Manual

5.11 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.

5.11.1 Hard Wire Base Block (HWBB) Function

The Hard Wire Base Block function (hereinafter referred to as HWBB function) is a safety function designed
to baseblock the motor (shut off the motor current) by using the hardwired circuits: Each circuit for two chan-
nel input signals blocks the run signal to turn off the power module, and the motor current is shut off. (Refer to
the diagram below.)
24-V power supply
(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 Category3
IEC61508 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 may move within the electric angle of 180 degrees in case of the power module failure, etc. The
number of rotations or movement distance depends on the motor type as shown below.
Rotary motor: 1/6 rotation max. (rotation angle at the motor shaft)
Direct-drive motor:1/20 rotation max. (rotation angle at the motor shaft)
Linear motor: 30 mm max.
• The HWBB function does not shut off the power to the servo drive or electrically isolates it. Take measures
to shut off the power to the servo drive when performing maintenance on it, etc.
Switch
SERVOPACK
/HWBB1+ 4
Fuse
/HWBB1-
3
/HWBB2+
6
/HWBB2-
5
0 V
Power supply
Control circuit
Run signal
Block
Block
Power module
Motor

5.11 Safety Function

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