Using the safety functions

Attention

Activating SBC independently of or with a delay to STO is not possible.
When STO is active SBC will also be activated, if a brake is connected it will be engaged.

To prevent damaging the brake, a Safe Stop Category 1 (SS1) is recommended.

Timing diagrams

Timing diagram for STO-function without connected brake

../../../../_images/timing_sto2.png

Timing diagram for STO-function with SBC-function

../../../../_images/timing_sto-sbc2.png

Truth table for digital inputs

STO-SBC In 1

STO-SBC In 2

Internal fault

Safety Statusword

Error entry

0

0

no

1

0

1

no

1

“SfeDilvd”

1

0

no

1

“SfeDilvd”

1

1

no

0

0

0

yes

1

“SfeFault”

Diagnostic functions

Software diagnostics

The safety circuit has two integrated diagnostic functions:

  • Comparing safety digital input statuses. The fault is activated after 100ms discrepancy of the STO-SBC inputs. In case a fault is detected, the servo drive will stop the motor and indicate a fault “SfeDilvd” in the Error Report object.

  • During the activation of the STO-SBC function the servo drive verifies that the two channels of the module are internally operating correctly. In case an internal fault is detected, the servo drive will stop the motor and indicate a fault “SfeFault” in the Error Report object.

STO-SBC status register

The Safety Statusword indicates the current state of safety functions and Safety Digital Input Diagnostics shows the state of the safety inputs.

Index

Name

Descriptions

0x6621

Safety Statusword

Subindex:

1 - Bit 1: STO status is the first bit of byte

2 - Bit 2: SBC status is the first bit of byte

STO/SBC status:

0: is not active

1: is active

0x2611

Safety Digital Input Diagnostics

Subindex:

1 - Input 1:

2 - Input 2:

Input 1/2:

0: Input is low

1: Input is high

Note

Using the SBC function while running the motor may damage the brake due to mechanical stress. During normal operation it is recommended to activate STO-SBC after the motor has come to a halt e.g. by introducing a delay with an external safety logic device such as a safety timer. This way an equivalent of SS1 with time monitoring is implemented.

Attention

The STO-function does not provide electrical isolation from the mains supply. If electrical changes need to be carried out on the system (e.g. modifying the motor cabling), the servo drive shall be completely isolated from mains supply with a mechanical switch.