Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) Commissioning - ForGe Control - Manual (Page 110)

110 Rockwell Automation Publication 7000-IN012B-EN-P - June 2014
Chapter 4 Commissioning the Drive
• Regulator Limit - indicates that the torque command was greater than Trq
Lmt Motoring or Trq Lmt Braking. The measured inertia value is invalid.
Parameter Autotune Trq Stp or parameter Autotune Spd Cmd must be set
to a lower value and the test repeated.
• Tuning Abort - indicates that the deviation in motor speed was greater
than 10 Hz. The measured inertia value is invalid. Parameter Autotune Trq
Stp must be set to a lower value and the test repeated.
• Inertia high - indicates that the measured total inertia is greater than
20 seconds. This warning is intended to draw attention to an unusually
high inertia value. For a very high inertia load such as a large fan, this may
be a valid result and parameter Total Inertia should be manually set equal
to Autotune Inertia. However, a high inertia measurement could also be
produced by a value of Autotune Trq Stp which is too low.
Running the Load Motor Starting Torque
When starting without an encoder, the drive operates in an open loop mode
below approx. 3 Hz at which point the drive switches to closed loop speed
control. The starting currents are set by three parameters; Torque Command 0
sensorless (P#86), Torque Command 1 Sensorless (P#87), Torque Command 0
sensorless sets the breakaway torque and Torque Command 1 sensorless is the
torque at the transition point from open to closed loop. Torque Command
Minimum operates in conjunction with Torque Command 1 to minimize speed
overshoot at the transition point. If you are starting an unloaded but coupled
motor, or simply auto-tuning, the default starting torque values may be sufficient
to run the motor. But the defaults are generally not high enough to start a loaded
motor. If the motor is uncoupled, the default values might be too high; reduce the
values to 0.10 pu (when motor is uncoupled). The alternative is to change the
operating mode to “Uncoupled Mtr”.
Be prepared to have to increase starting torque and ensure Motor Stall faults
during initial operation.
Reaching Specific Load Points
Verify the drive can reach rated speed and load. Monitor the Torque Reference
(P#291) and the displayed value of the motor current. If you are running into a
torque limit the Torque Reference will be running near the Torque Limit
Motoring (P#84) limit. If you are not realizing rated motor current you may
increase the Torque Limit Motoring slightly. If increasing the Torque Limit
Motoring does not help to increase the motor amps and speed then the drive is
most likely running out of input voltage.