Safety Concept; Functional Description; Safety Precautions - Danfoss VLT ISD 511 Operating Manual

VLT® Servo Drive System ISD 511
Operating Guide

8 Safety Concept

8.1 Functional Description

The servo system integrates the safety function Safe Torque Off (STO). The safety function is available in daisy-chain format, which is
possible between all system modules except ACM 510 (cables are not included). The hybrid cable passes the STO signal from the
Decentral Access Module (DAM 510) to all ISD 511 servo drives in the chain. Once STO is activated (safe state), no torque is gener-
ated on the ISD 511 servo drives. Reset of the safety function and diagnostics can be carried out via the PLC.
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Use STO shielded wiring.
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Use the STO function when performing mechanical work on the servo system or affected area of a machine to avoid a me-
chanical hazard. However, the STO function does not provide electrical safety.

8.2 Safety Precautions

UNCONTROLLED MOVEMENT
External forces on the motor could cause an uncontrolled and hazardous movement that could result in death or serious injury.
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Equip the motor with additional measures for preventing uncontrolled and hazardous movement, for example mechanical
brakes.
RISK OF ELECTRICAL SHOCK
The STO function does not isolate mains voltage to the servo system or auxiliary circuits. Failure to isolate the mains voltage
supply and wait for the specified discharge time to elapse could result in death or serious injury.
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Only perform work on electrical parts of the system or the ISD 511 drives after isolating the mains voltage supply and waiting
for the discharge time to elapse.
RISK OF RESIDUAL ROTATION
Due to failures in the power semiconductor of the drive, a residual rotation can result from a fault that could result in death or
serious injury. The rotation can be calculated to angle = 360°/(number of poles).
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Take this residual rotation into consideration and ensure that it does not pose a safety risk.
LED STATUS RELIABILITY
Status indicators (LEDs) are not reliable for safety functions.
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Only use status indicators for general diagnostics during commissioning and troubleshooting.
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After installing the STO function, perform a commissioning test. A passed commissioning test is mandatory after initial instal-
lation and after each change to the safety installation (see
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If required, implement a manual reset function according to EN ISO 13849-1. For automatic restart without manual reset,
observe the requirements detailed in paragraph 6.3.3.2.5 of EN ISO 12100:2010 or equivalent standard.
Danfoss A/S © 2023.08
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8.8 Commissioning
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Safety Concept