Rockwell Automation Publication MOTION-RM003I-EN-P - February 2018 445
When the Auto Sag Configuration attribute is set to Enabled, this attribute is used
to enable the Auto Sag function in the Stopped or Faulted state. When Auto Sag
Start is enabled, the drive monitors the load for possible brake slip and should the
amount of brake slip exceed the Brake Slip Tolerance a Brake Slip exception is
generated, along with a Brake Malfunction start inhibit. When this occurs, the
drive power structure is enabled (Started) without holding torque and the axis
transitions to the Aborting State. The drive continues to monitor brake slip and
when the amount of slip exceeds the Auto Sag Slip Increment holding torque is
applied to the motor to arrest the brake slip. The drive then ramps the motor
torque to zero based on the Brake Prove Ramp Time while again checking for slip.
Should brake slip continue and exceed the Auto Sag Slip Increment, holding
torque is applied and the cycle repeats. In crane and lift applications, this repeating
"Auto Sag" cycle is designed to lower the load in a controlled series of Auto Sag
Slip Increments until the load reaches the ground.
See also
Stopping Sequences on page 445
Proving Operation Sequences on page 448
State Behavior on page 61
Motor Attributes on page 57
CIP Axis Attributes on page 185
There are three different stopping sequences defined for stopping and braking
related attributes. These three stopping sequences align with the following
IEC-60204-1 Stop Categories:
• Category 0 Stop: Drive immediately disables inverter power structure.
• Category 1 Stop: Drive decelerates motor to a stop and then disables power
structure.
• Category 2 Stop: Drive decelerates motor to a stop and then applies holding
torque.
All actions initiated by the control or the drive to stop the axis or disable its
associated inverter power structure must execute one of these three stopping
sequences. Category 0 and Category 1 Stop sequences coordinate the disabling of
the drive power structure with brake operation and in some cases, optional Brake
Proving functionality.
The following stopping sequences are defined in the context of a Disable Request
generated stop, where the stopping methods are applied in the Stopping state and
the stopping sequences ends up in the Stopped state. In the context of a Major
Fault action, these same stopping methods are applied in the Aborting state and
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