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Option description 15
3
Option description
Contents of this chapter
This chapter describes the option +Q950, prevention of unexpected start-up, and its settings.
Overview
The option +Q950 uses the FSO-12 safety functions module (option +Q973) or the FSO-21
safety functions module (option +Q972) for the Prevention of unexpected start-up (POUS)
safety function. ABB installs the FSO modules to the inverter units and sets default parameter
values for the option at the factory. The user installs and wires an operating switch and an
indication lamp (optional) on site. These are not included in the delivery.
The user activates the POUS function with an operating switch mounted, for example, on
a control desk. When the switch is open (off), the POUS function is active and the POUS
indication lamp is on.
When the user switches off the POUS switch, the Safe torque off (STO) function in the
inverter units is activated. The STO function disables the control voltage of the power
semiconductors of the inverter unit output stage. This prevents the inverter units from
generating the torque required to rotate the motor(s). With this 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 inverter units.
Note: Drives with the Emergency stop, stop category 1 function (option +Q979): If the user
activates the POUS function during the emergency stop deceleration ramp, it overrides the
emergency stop function. This activates the STO function of the inverter unit and the motor
coasts to a stop. For more information on the emergency stop function, see Emergency
stop, configurable stop category 0 or 1 (option +Q979) for ACS880 multidrives user's manual
(3AUA0000145933 [English]).
For a detailed description of the Safe torque off function, see the inverter unit hardware
manual. For more information on the FSO module, see FSO-12 safety functions module
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