Danfoss VLT series Operating Instructions Manual - Page 8
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Safety
WARNING
SAFE TORQUE OFF FUNCTION
2
2
The Safe Torque Off function does NOT isolate mains
voltage to the frequency converter or auxiliary circuits.
Perform work on electrical parts of the frequency
converter or the motor only after isolating the mains
voltage supply and waiting the length of time specified
in the Safety Chapter in the relevant Operating
Instructions. 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 frequency converter by using the
Safe Torque Off function. If a running frequency
converter is stopped by using the function, the
unit trips and stops by coasting. If this is not
acceptable, e.g. causes danger, stop the
frequency converter and machinery by using the
appropriate stopping mode before using this
function. Depending on the application, a
mechanical brake may be required.
•
Safe Torque Off is suitable for performing
mechanical work on the frequency converter
system or affected area of a machine only. It does
not provide electrical safety. Safe Torque Off
should not be used as a control for starting
and/or stopping the frequency converter.
CAUTION
Automatic restart behaviour is only allowed in 1 of the 2
situations:
1.
The unintended restart prevention is
implemented by other parts of the Safe Torque
Off installation.
2.
A presence in the dangerous zone can be
physically excluded when Safe Torque Off is not
activated. In particular, paragraph 5.3.2.5 of ISO
12100-2 2003 must be observed.
WARNING
The Safe Torque Off function can be used for
asynchronous, synchronous and permanent magnet
motors. 2 faults can occur in the power semiconductor of
the frequency converter. 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 motors must take
this residual rotation into consideration and ensure that
it does not pose a safety risk. This situation is not
relevant for asynchronous motors. Risk of death and
serious injury.
6
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VLT
Frequency Converters - Safe Torque Off Operating Instructions
NOTICE
The selection of a stop category in accordance with EN
60204-1 for each stop function must be determined by a
risk assessment:
•
•
•
NOTICE
When designing the machine application, timing and
distance should be considered for a coast to stop (Stop
Category 0 or Safe Torque Off). For more information
regarding stop categories, refer to EN 60204-1.
MG37D102 - Rev. 2013-11-15
Stop Category 0 is achieved with immediate
removal of power to the actuator, resulting in
an uncontrolled coast to stop. Safe Torque Off
(STO) according to EN 61800-5-2 accomplishes a
Stop Category 0 stop.
Stop Category 1 is achieved with power
available to the machine actuators to achieve
the stop. Power is removed from the actuators
when the stop is achieved according to EN
61800-5-2 Safe Stop 1 (SS1).
Stop Category 2 is a controlled stop with power
available to the machine actuators. The stop is
followed by a holding position under power.