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W A R N I N G
FALL PROTECTION REQUIRED
External forces acting on the motor, for example suspended loads, and unintended movements, for example caused by gravity,
can cause hazards. Not taking any measures to protect against falling loads can lead to death or serious injury.
Equip the motor with extra measures for fall protection, for example, install extra mechanical brakes.
W A R N I N G
NO ELECTRICAL SAFETY
STO (that is, removal of 24 V DC voltage supply to terminal 37) does not provide electrical safety. The STO function itself is not
sufficient to implement the Emergency-Off function as defined by EN 60204-1. Using the STO function to implement Emergency-
Off may lead to personal injury.
Emergency-Off requires measures of electrical isolation, for example, by switching off mains via an extra contactor.
W A R N I N G
RISK OF ELECTRICAL SHOCK
The STO function does NOT isolate mains voltage to the drive or auxiliary circuits. Only perform work on electrical parts of the
drive or the motor after isolating the mains voltage supply and waiting for the discharge time to elapse, as specified in the
Safety
chapter in the Operating Guide of the relevant drive. Failure to isolate the mains voltage supply from the unit and waiting the
time specified could result in death or serious injury.
Do not stop the drive by using the STO function. If a running drive is stopped by using the function, the unit trips and stops
by coasting. If this limitation is not acceptable, for example because it causes danger, use the appropriate stopping mode to
stop the drive and machinery before using the STO function. Depending on the application, a mechanical brake may be re-
quired.
STO is suitable for performing mechanical work on the drive system or affected area of a machine only. It does not provide
electrical safety. STO must not be used as a control for starting and/or stopping the drive.
W A R N I N G
RESIDUAL ROTATION
The STO function can be used for asynchronous, synchronous, and permanent magnet motors. Two faults can occur in the power
semiconductor of the drive. When using synchronous or permanent magnet motors, a residual rotation can result from the faults.
The rotation can be calculated to angle = 360/(number of poles). The application using synchronous or permanent magnet mo-
tors must consider this residual rotation and ensure that it does not pose a safety risk. The situation is not relevant for asynchro-
nous motors.
C A U T I O N
After installing STO, perform a commissioning test. A passed commissioning test is mandatory after the 1
st
installation and after
each change to the safety installation.
C A U T I O N
AUTOMATIC RESTART
Automatic restart behavior is only allowed in 1 of the 2 situations:
The unintended restart prevention is implemented by other parts of the STO installation.
A presence in the dangerous zone can be physically excluded when STO is not activated. In particular, observe paragraph
6.3.3.2.5 of ISO 12100:2010.
AQ313340186453en-00101 / 130R0544
8 | Danfoss A/S © 2021.03
Safety
Safe Torque Off
Operating Guide
