Planning the electrical installation
71
Safe torque off
The drive supports the Safe torque off function according to standards EN 61800-5-
2:2007; EN ISO 13849-1:2008, IEC 61508, IEC 61511:2004 and EN 62061:2005.
The function also corresponds to prevention of unexpected start-up of EN 1037.
The Safe torque off function disables the control voltage of the power
semiconductors of the drive output stage, thus preventing the inverter from
generating the voltage required to rotate the motor. By using this function, short-time
operations (like cleaning) and/or maintenance work on non-electrical parts of the
machinery can be performed without switching off the power supply to the drive.
For more information, see Safety options for ACS800 cabinet-installed drives
(+Q950, +Q951, +Q952, +Q963, +Q964, +Q967 and +Q968): Wiring, start-up and
operation instructions (3AUA0000026238 [English]).
WARNING! The Safe torque off function does not disconnect the voltage of the main
and auxiliary circuits from the drive. Therefore maintenance work on electrical parts
of the drive or the motor can only be carried out after isolating the drive system from
the main supply.
Note: It is not recommended to stop the drive by using the Safe torque off function. If
a running drive is stopped by using the Safe torque off function, the drive will stop by
coasting. If this causes danger or is not acceptable, the drive and machinery must be
stopped using the appropriate stopping mode before using the Safe torque off
function.
Note concerning permanent magnet motor drives in case of a multiple IGBT
power semiconductor failure: In spite of the activation of the Safe torque off
function, the drive system can produce an alignment torque which maximally rotates
the motor shaft by 180/p degrees. p denotes the pole pair number.
ATEX-certified thermal motor protection
The drive can be optionally equipped for ATEX-certified thermal motor protection.
The option includes the necessary safety relays and internal wiring. (The sensors or
sensor wiring are not included.)
The motor is located in a potentially explosive atmosphere. PTC or Pt100 sensors in
the bearings and/or stator winding of the motor are wired to the drive, which is
located outside the hazardous zone. When the motor temperature exceeds a certain
limit, the safety relay activates the Safe torque off function.
For more information, see ATEX-certified thermal motor protection functions for
ACS800 cabinet-installed drives (+L513+Q971 and +L514+Q971): Safety, wiring,
start-up and operation instructions (3AUA0000082378 [English]).
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