Eliminated from:
Inverter Drives 8400 TopLine from firmware version 12.01.00.00
Behaviour of the new version?
The speed controller works with the correct actual value.
If the speed setpoint is n=0rpm, there is no drift at the motor shaft anymore.
Which products are affected?
Inverter Drives 8400 TopLine with a firmware version 12.00.00.00
What is the reaction?
The motor shaft rotates with approximately 0.1rpm in CCW direction although the speed setpoint is nSet=0rpm. This can also be the case if quick stop is activated (bQSPActive=TRUE).
When does the problem occur?
If a resolver is used as speed feedback, and during a mere speed-controlled operation without a higher-level position control.
Diagnostics options?
In spite of M LS_MotionControlKernel.bQSPOn=TRUE, a position change in negative direction can be observed at LS_MotorInterface.dnMotorPosAct_p
In spite of an I component in the speed controller, the torque generated is not sufficient to hold the shaft at standstill.
Short-term measures/recommendations?
When quick stop is active, the drift of the motor shaft at standstill can be prevented by activation of the position control. This requires the following settings
• Select available position encoder, e.g. C490=4 'Resolver'
• Setting quick stop C104 bit1 =True 'Position-controlled standstill'
• Depending on the load ratio, it may be required to adapt the gain in the position controller; Kp position controller C254.
• Connect values > 0% e.g. 100% to nPosCtrlOutLimit_a nPosCtrlPAdaptLimit_a at LS_MotorInterface
A standstill in mere speed control with nSet=0rpm cannot be achieved.
Evaluation:
A movement of the motor shaft in the case of a digital setpoint selection nSet=0rpm and a servo drive with speed feedback is not expected. The impact of the speed drift depends on the application. Material or tool damage is possible. Limited travel ranges or travel ranges with the risk of collision should usually be protected by further monitoring functions such as a following error and/or a limit position monitoring and/or safety devices.
In the case of applications with a position control in the inverter or an external position control (e.g. path control), a standstill is achieved by the correcting variable of the position controller.
