Option Description; Contents Of This Chapter; Overview - ABB Q957 User Manual

Option description 15

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Option description

Contents of this chapter

This chapter describes the option +Q957, prevention of unexpected start-up, and its settings.

Overview

The option +Q957 uses a safety relay to implement the Prevention of unexpected start-up
(POUS) safety function. ABB installs the safety relay to the drive at the factory.
The user must install and connect an operating switch and an indication lamp (optional) on
site. These are not included in the delivery. The user can install the operating switch on, for
example, a control desk. See the machine-specific C-type standards on whether the indication
lamp is required.
When the user sets the operating switch to the open position, the POUS function activates
the Safe torque off (STO) function in the drive. The Safe torque off function disables the
control voltage of the power semiconductors of the drive output stage. This prevents the
drive from generating the torque required to rotate the motor. With the POUS function, the
user can do short-time operations (like cleaning) or maintenance work on the non-electrical
parts of the machinery without switching off and disconnecting the drive.
Note: The situations in which you can use the POUS function must always be based on a
risk assessment. Refer to IEC 60204-1:2016.
Note: Drives with the Emergency stop, stop category 1 function (option +Q952 or +Q964):
If the user activates the POUS function during the emergency stop deceleration ramp, it
overrides the emergency stop function. This activates the drive STO function immediately
and the motor coasts to a stop. For more information on the emergency stop function, see
the applicable user's manual.