ABB ACS850 Firmware Manual page 21

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.
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 (brake chopper and brake resistor) is needed in
some applications to allow the drive to dissipate regenerative energy. The chopper connects
the brake 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 brake resistor (the drive has a
built-in brake chopper):
• Set the brake chopper and resistor settings.
Note: When a brake chopper and resistor are used, the
overvoltage controller must be deactivated by parameter
47.01 Overvolt ctrl.
• Check that the connection is functioning.
For more information on the brake resistor connection,
see the appropriate hardware manual.
Select the start function.
Setting 11.01 Start mode
purpose start function. This setting also makes flying start
(starting to a rotating motor) possible.
The highest possible starting torque is achieved when
11.01 Start mode
magnetising) or
with user-defined magnetising time).
Note: When 11.01 Start mode
flying start (start to a rotating motor) is not possible.
Safe Torque Off
Voltage control
Start function
to Automatic selects a general-
is set to Fast (automatic optimised DC
Const time (constant DC magnetising
is set to Fast
30.07 Sto diagnostic
47.01 Overvolt ctrl
47.02 Undervolt ctrl
48.01...48.07
47.01 Overvolt ctrl
11.01 Start mode
or Const time,
Start-up 21