3.5.3 Safe Torque Off - STO
The safety function Safe Torque Off disconnects power to
the motor. It is implemented via the frequency converter's
shutdown path and the safety option’s safe outputs.
Features of the safety function
•
The motor becomes torque-free and no longer
generates any hazardous movements
•
To prevent the frequency converter from running
down in an uncontrolled manner. In normal
operation, activate the safety function Safe
Torque Off via the safety function Safe Stop 1
•
Safe Torque Off is only activated directly when
-
There is an internal error on the safety
option
-
The Safe Stop 1 delay time is set to 0
-
One of the inputs DI1 or DI2 has been
selected as Safe Torque Off function
•
The safety function Safe Torque Off corresponds
to a category 0 stop (uncontrolled stop) in
accordance with EN IEC 60204-1.
Prerequisites for normal operation
•
Input DI1 or DI2: "1" Signal (+24 V DC)
•
S37 output: "1" Signal (+24 V DC).
Safety function is activated
•
By an error after limit values have been exceeded
for Safe Stop 1 and Safely Limited Speed
•
By an internal error on the safety option or
frequency converter, if the frequency converter
can no longer be controlled
•
By executing the safety function Safe Stop 1 (1/0
transition). In this case the frequency converter is
monitored before it is switched to torque-free.
•
By download of parameterisation via MCT 10 Safe
Plug-in if the current frequency converter is
running.
•
By executing the safety function Safe Torque Off
(1/0 transition). This function ensures that no
torque-generating energy can continue to affect a
motor and prevents unintentional start-ups.
WARNING
If any external forces influence the motor axis (e.g.
suspended loads), additional measures (e.g. a safety
holding brake) are required to eliminate hazards.
The Safe Torque Off (STO) may be used where power
removal is required to prevent an unintended start. The
function disables the control voltage of the frequency
converter output stage. Thus, it prevents the frequency
converter from generating the voltage required to rotate
the motor (see
). The function allows for
performing maintenance work on non-electrical parts of
the machinery without switching off the power supply to
the frequency converter.
fr
equen
cy
130BC318.10
time
1
2
A
A
Actual frequency
1
Activation of Safe Torque Off
2
Motor standstill
Illustration 3.6 Safe Torque Off
3.5.4 Safe Stop 1 - SS1
The safety function Safe Stop 1 monitors the deceleration
to zero speed in a controlled manner and activates Safe
Torque Off after detection of stop. The Safe Stop 1 can
either be configured as SS1 Delay or SS1 Ramp.
Features of the safety function
•
The safety function Safe Stop 1 corresponds to a
category 1 stop (controlled braking) in
accordance with EN IEC 60204-1
•
Monitoring the speed deceleration after which
the energy supply to the motor is safely
interrupted
•
The motor becomes torque-free and removes
hazardous movements
3.5.4.1 SS1 Delay
Select SS1 Delay to activate Safe Stop 1 function while a
parameterised safety delay timer expires.
Functions and System Overvi...
Operating Instructions
MG34W302
Danfoss A/S © Rev. 2014-02-11 All rights reserved.
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