8 Introduction to the guide
Safety instructions
WARNING! Read and follow all safety instructions given for the drive. Ignoring the
safety instructions can cause physical injury or death, or damage to the
equipment.
This manual does not repeat the complete safety instructions of the drive but summarizes
the instructions related to the ATEX-certified Safe disconnection function. The general
instructions are given in this section and the option-specific instructions in the appropriate
chapter.
In addition to this manual, see the drive hardware manual.
Never work on the drive, the braking chopper circuit, the motor cable or the motor when
input power is applied to the drive. Always ensure by measuring that no voltage is actually
present.
The safety function described in this guide activates the Safe torque off (STO) function of
the drive/inverter module. The STO function of the ACS850 drives is certified (SIL 3
according to EN/ IEC 61800-5-2 and IEC 61508). For a detailed description of the STO
function, see the hardware manual of your drive/inverter module.
WARNING! The functions described in this guide do not disconnect the voltage of
the main and auxiliary circuits from the drive. Never work on the electrical parts of
the drive or the motor before you have also disconnected the drive system from
the electric supply, from rotating permanent magnet motors and from rotating motors
equipped with sine filters, and made sure by measuring that there is no dangerous voltage
present.
WARNING! The Safe torque off feature of ACS850 drives cannot prevent the
intermediate DC current from flowing through, and heating up, the motor in case a
short-circuit occurs in the output stage of the drive. The supplier must take this
into account when planning the protection of the installation.
Note: When you connect the temperature sensor(s) of the Ex motor to the drive STO
terminals through a relay, ensure the availability of required reinforced (double) insulation
between the main circuit (motor) and the control unit. For example, the insulation of the
temperature sensor in the Ex motor and the insulation of the protection relay affect the
insulation of the whole circuit. All Ex motors manufactured by ABB have basic insulation
between the main circuit and the temperature sensor. Similarly, ABB thermistor relays
have basic insulation between the sensor circuit and relay output. This ensures double
insulation for the ATEX-certified motor thermal protection function between the main circuit
and the drive control unit.
The ATEX-certified Safe disconnection function
When the drive/inverter module is equipped with the option +Q971, its Safe torque off
(STO) function is certified as a Safe disconnection function. It can be used as a protective
system to protect equipment in potentially explosive atmospheres. The certificate is an EU
Type examination certificate in accordance with the ATEX Product Directive 2014/34/EU
(previously 94/9/EC).
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