ABB ACSM1 Firmware Manual page 24

24
The Safe Torque Off function disables the control voltage of the power semiconductors of the drive
output stage, thus preventing the inverter from generating the voltage required to rotate the motor.
For Safe Torque Off wiring, see the appropriate hardware manual and Application guide - Safe
torque off function for ACSM1, ACS850 and ACQ810 drives (3AFE68929814 [English]).
If there is a Safe Torque Off circuit in use, check that the circuit
functions.
Selects how the drive reacts when the Safe Torque Off function is
active (i.e. when the control voltage of the power semiconductors of
the drive output stage is disabled).
If the DC voltage drops due to input power cut off, the undervoltage controller will automatically
decrease the motor torque in order to keep the voltage above the lower limit.
To prevent the DC voltage from exceeding the overvoltage control limit, the overvoltage controller
automatically decreases the generating torque when the limit is reached.
When the overvoltage controller is limiting the generating torque, quick deceleration of the motor is
not possible. Thus electrical braking (braking chopper and braking resistor) is needed in some
applications to allow the drive to dissipate regenerative energy. The chopper connects the braking
resistor to the intermediate circuit of the drive whenever the DC voltage exceeds the maximum limit.
Check that the overvoltage and undervoltage controllers are active.
If the application requires a braking resistor (the drive has a built-in
braking chopper):
• Set the braking chopper and resistor settings.
Note: When a braking chopper and resistor are used, the overvoltage
controller must be deactivated by parameter
CTRL.
• Check that the connection functions.
For more information on the braking resistor connection, see the
appropriate hardware manual.
Start-up
Safe Torque Off
Voltage control
47.01 OVERVOLTAGE
46.07 STO DIAGNOSTIC
47.01 OVERVOLTAGE
CTRL
47.02 UNDERVOLT
CTRL
48.01...48.07
47.01 OVERVOLTAGE
CTRL