Stopping Sequences

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 above stopping sequences are listed in order of precedence should a stopping sequence be initiated while another stopping sequence is in progress. For example, a Category 0 stopping sequence shall preempt a Category 1 stopping sequence in progress, but a Category 1 stopping sequence shall not supersede a Category 0 stopping sequence in progress. This rule of precedence holds true regardless of the source that initiated the stopping sequence.
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 the stopping sequences end up in the Major Faulted state. In the context of a Shutdown Request, the Category 0 stopping method below is applied in the Stopping state and the stopping sequence ends up in Shutdown state.
Category 0 Stop Sequence
Inverter is immediately disabled. Brake Proving is not applicable.
  1. Switch to Stopping state
  2. Disable inverter power structure.
  3. Deactivate Resistive Brake contactor to connect motor to brake resistor, if applicable.
  4. Wait for zero speed or "Coasting Time Limit" or a factory set timeout, whichever occurs first.
  5. Transition to Stopped state.
  6. Deactivate Mechanical Brake output to engage brake, if applicable.
The following diagram illustrates Category 0 Stop Sequence:
Brake Control Sequence - Category 0 Stop
Category 1 Stop Sequence
Torque applied to stop the motor before the inverter is disabled. Brake Proving is applicable.
  1. Switch to Stopping state.
  2. Apply "Current Decel" or "Ramp Decel" method to stop motor.
  3. Wait for zero speed or 'Stopping Time Limit' or a factory set timeout, whichever occurs first.
  4. Deactivate Mechanical Brake output to engage brake.
  5. Wait for "Mechanical Brake Engage Delay" while brake engages.
  6. Perform (optional) Brake Proving operation to verify brake control of load.
  7. Disable inverter power structure.
  8. Transition to Stopped state.
  9. Deactivate Resistive Brake contactor to disconnect motor from inverter power structure.
The following diagram illustrates a Category 1 Stop Sequence:
Brake Control Sequence - Category 1 Stop
Category 2 Stop Sequence
Torque is applied to stop the motor and inverter is left enabled to provide holding torque. The mechanical brake is not used. Brake Proving is not applicable. A Category 2 Stop is only allowed in no Start Inhibit condition is present.
  1. Switch to Stopping state.
  2. Apply "Current Decel" or "Ramp Decel" method to stop motor.
  3. Wait for zero speed or "Stopping Time Limit" or a factory set timeout, whichever occurs first.
  4. Transition to Stopped state.
A Category 2 stop sequence is not allowed if initiated by a Disable Request or fault action with a Start Inhibit condition present. If a Start Inhibit condition is present, a Category 1 stop sequence is initiated instead, using the same stopping method (Current Decel or Ramped Decel) that would have been applied by the Category 2 stop sequence. Category 2 stop sequences are also not allowed if initiated by a Start Inhibit condition with the axis in the Stopped state or Major Faulted state with Holding torque. In this case, the drive initiates a Category 1 stop sequence instead, using the same stopping method (Current Decel or Ramped Decel) that would have been applied by the configured Category 2 Stopping Action.
The following diagram illustrates a Category 2 Stop Sequence:
Brake Control Sequence - Category 2 Stop
TIP: Recommended criteria for Zero Speed is based on Velocity Feedback, or in the case of Frequency Control drive, based on Velocity Reference. Zero Speed criteria can be established explicitly through optional Zero Speed and Zero Speed Time attributes or implicitly as 1% of motor rated speed or left to the drive vendor’s discretion.
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