Speed Discrepancy With Multiple Speed Sources; Encoders - Danfoss Vacon OPTEA Operating Manual

VACON® NXP Advanced Safety Options
Operating Guide

3.6.3 Speed Discrepancy with Multiple Speed Sources

When you use multiple speed sources, for example, a Sin/Cos encoder and a proximity sensor, or estimated speed and a speed
sensor, the speed values measured by these sensors must be within the allowed deviation of each other.
There is new behavior in the software version FW0281 V004: the reaction to exceeding the deviation depends on the request for
safety functions. If a safety function is requested, the reaction is a fault and STO will be activated. If no safety function is requested,
the reaction is a warning and STO will not be activated. This enables continuing the process and stopping at an acceptable and safe
position. It is also possible to start a single drive in already running process where there is a difference in estimated speed and en-
coder speed before the drive enters run mode, that is, a "flying start" situation.
INSUFFICIENT SPEED MEASUREMENT CAPACITY
When the warning for speed difference is active, the safety system cannot guarantee that the speed measuring capability is suffi-
cient.
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Running in this mode should be kept to minimal, for example to only start the motor in "flying start" situation or to continue
to a safe position.
If running the motor in this situation cannot be accepted, a possible solution is to use the Safe Speed Monitor (SSM) safety function.
It can be set to "Always active" mode. So, the safety function is always requested and the reaction to speed discrepancy is always
fault and STO. This is the same as the behavior in the previous software version (FW0281 V003 and older).
The value for the allowed deviation between the speeds can be set during parameterization. A formula for a recommended value
with a speed sensor and estimated speed can be found in chapter Estimated speed.

3.6.4 Encoders

The encoder interface boards of the Advanced safety option board have two connector sets. The cables from an encoder are con-
nected to one connector set. The other connector set provides the encoder signals as output that can be connected to other devi-
ces that use the encoder data. Such device can be, for example the standard encoder board that is used to realize the closed-loop
control. The Advanced safety option board transmits the signals from the encoder to the other connector set without any modifica-
tion.
When you use speed sensors for the safety functions, it is possible that the AC drive operates in open loop or closed-loop control.
When closed-loop control is used, a closed-loop enabling option board must be used in slot C. This can be either a separate en-
coder board or the Advanced Safety Option.
When you use speed sensors without SIL claims, estimated speed from the AC drive can be used as a second independent chan-
nel to fulfill the requirements of safety standards. See chapter Standard Speed Sensors and Combinations.
The encoder signals consist of two separate channels (for example, sinus and cosine). Do not change the order or modify the
channels before connecting them to the Advanced safety option.
When the Advanced Safety Option is used for closed-loop control, it must be installed in slot C. Connect the encoder cables to the
board normally.
When closed-loop control is used with a separate encoder board, connect the SinCos/Digital pulse signal cables of the encoder to
the encoder interface board of the Advanced safety option board. Connect also the encoder interface board to the encoder board in
slot C. The encoder board implements the closed-loop control by using the encoder interface board to receive feedback. See the
figure below.
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