SINUS PENTA
PENTA MARINE
IRIS BLUE
STO FUNCTION
APPLICATION MANUAL
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1. BASICS
1.1.
General
The Santerno Sinus Penta, Penta Marine and Iris Blue inverter product lines, now equipped with the new
ES927 control board, support the Safety Torque Off (STO) function. This document instructs the user on
how to properly apply the Safety Torque Off (STO) function implemented on the inverters.
The above mentioned inverters allow adjusting speed and torque values of three-phase asynchronous
motors and brushless permanent-magnet AC motors with several control modes. Control modes may be
user-defined and allow obtaining the best performances in terms of fine-tuning and energy saving for any
industrial application.
The Safe Torque Off (STO) function, integrated in these product lines, is a particular stopping method
defined in clause 4.2.2.2 of EN 61800-5-2 (2007-10), as listed below:
“4.2.2.2 Safe Torque Off (STO)
Power, that can cause rotation (or motion in the case of a linear motor), is not applied to the motor. The
PDS(SR) (Power Drive System Safety-Related) will not provide energy to the motor which can generate
torque (or force in the case of a linear motor).
NOTE 1
This safety function corresponds to an uncontrolled stop in accordance with stop category
0 of IEC 60204-1.
NOTE 2
This safety function may be used where power removal is required to prevent an
unexpected start up.
NOTE 3
In circumstances where external influences (for example, falling of suspended loads) are
present, additional measures (for example mechanical brakes) may be necessary to prevent any hazard.
NOTE 4
Electronic means and contactors are not adequate for protection against electric shock,
and additional measures for isolation may be necessary.”
The STO is a function that allows stopping the motor in a safe way if externally demanded. The STO
function removes power from the motor by disabling the PWM commands from the CPU to the IGBT
drivers.
The STO function can be used also to prevent unexpected start up of the motor.
The STO function in the Sinus Penta, Penta Marine and Iris Blue drives is obtained at a hardware level
and its activation is absolutely independent of the software and the CPU of the inverter. The drive
firmware implements only non-critical diagnostic functions related to the STO function.
Where external influences (for example, falling of suspended loads) are present, additional measures (for
example mechanical brakes) may be necessary to prevent any hazard.
WARNING
The Safe Torque Off function does not cut off the mains voltage 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 mains supply.
NOTE
The Safe Torque Off function can be used for stopping the drive in
emergency stop situations. In normal operating mode, it is recommended not
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 trip and perform
a coast to stop. If this is not acceptable, e.g. causes danger, the drive and
machinery must be stopped using the appropriate stopping mode instead of
adopting the STO function.
NOTE
Note concerning permanent magnet motor drives in case of multiple
IGBT power semiconductor failure:
Due to the possible DC output voltage present for certain multiple IGBT
failures, 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 is the pole pair number).
