Question:
How does the encoder-gearbox factor (C1207/x) influence the display range of the absolute value encoder?
Answer:
Hiperface absolute value encoders usually have a display range of 4096 encoder revolutions. The absolute position when the mains is switched on can be read out within this range. If the revolution range is exceeded an overflow of the absolute information occurs inside the encoder. When the mains is switched on again a wrong position value is read out.
The 9300EP position controller can internally display a range of approx. +/- 16000 motor revolutions (= 32000 rev.). The limit is determined by the 32-bit variable format and the requirements for a possible shift of the machine zero by means of the reference measuring offset.
C1207/x = 1/1 (default):
If the encoder-gearbox factor C1207/x is set to 1/1 (e. g.: encoder mounted to the motor shaft) the complete encoder range of 4096 revolutions can be used. A safety reserve to the overflow points should be observed.
C1207/x smaller 4/1:
The complete encoder range of 4096 revolutions can also be used up to an encoder-gearbox factor of 4/1, e. g. when the absolute value encoder is mounted to the machine.
In this case the motor makes 4 revolutions while the encoder rotates once only. The approx. 4000 encoder revolutions can just be displayed by the approx. 16000 controller revolutions (4000 x 4 = 16000).
C1207/x larger 4/1:
As of encoder-gearbox factors of 4/1 and higher the display range of the absolute value encoder which can actually be used becomes smaller and smaller when the factor increases.
The high encoder revolution values can then no longer be displayed inside the controller by the increments format of the 32-bit variables.
The number of encoder revolutions which can maximally be used can be calculated as follows:
- Max. revolution value = 16000 rpm * C1207/2 / C1207/1 (to be observed: denominator / numerator)
Example: C1207/1 = 75; C1207/2 = 3
- Max. revolution value = 16000 * 3 / 75
- Max. revolution value = 640 rev.
- The encoder range which can actually be used results in: 0...640 rev.
Important:
In case of large encoder-gearbox factors the Hiperface absolute value encoder must be mounted to the machine in such a way that the reduced encoder range will not be quit during operation.
A remedy as a result of shifting the home position C1227or reference measuring offset C1225 by using the software
cannot be provided.
Tip: In case of very large encoder-gearbox factors the consequences with regard to the control loop stability are to be observed, too.
