Eliminated from:
8400 TopLine: FW version = 13.00.00.00
Response of the new version?
Disrupted SinCos signals may cause momentary slight deviations of the actual position in the inverter, but the error can no longer integrate. A loss of the pole position information does not occur anymore.
Which products are affected?
8400 TopLine: FW version up to 12.01.00.00
What is the response?
When controlling a synchronous motor, typical indicators for an incorrectly set pole position show:
- Increased current consumption
- A different current consumption at the same load subject to the direction of rotation. This also falsifies the displayed torque calculated from the current.
- Acceleration of the motor in an unpredictable direction of rotation up to a speed which is only determined by the voltage limitation, and remaining at this speed.
When controlling an ASM, deviations between the MCK position and the actual machine position can be noticed.
When does the problem occur?
If SinCos signals are heavily interfered, due to a monitoring function the last position value in the encoder evaluation is discarded. Thus, depending on the previous position change/call (speed) of the evaluation, a correspondingly great position deviation takes place.
This position error causes deviations during the position control and/or unstable operation and, when controlling synchronous motor, an offset in the pole position.
Diagnostics options?
The cause of the position error can only be diagnosed with great difficulty. With regard to this response it is noticeable that, at first, operation can be trouble-free after mains switching and a pole position adjustment, and that the impacts of a position error or the pole position offset are only noticeable after longer operation.
Short-term measures/recommendations?
None.
Evaluation:The reference to the actual machine position is lost. In the case of position-based movements, the expected, actual machine positions are not approached. Software limit position monitoring functions do not respond as expected.
During operation with an incorrect pole position, in the worst case a synchronous motor may accelerate up to a speed at the voltage limit in an uncontrolled fashion. Monitoring functions with a 'Quick stop by trouble' response cannot stop the motor.
Such heavy interferences of the encoder SinCos signals may be caused by a control cabinet design and wiring not complying with EMC regulations, or also when the internal EMC filter is disconnected from PE (Y-capacitors), as is required for operation of the inverters in the IT system.
