•
•
•
•
•
•
•
•
•
•
•
•
•
•
Table 13: Recommended Minimum Limits
Minimum recommended speed limits (rpm)
3.6.6 Encoder Signal Verification
The Advanced safety option board verifies the correctness of the encoder signals. During the operation of the option board, the
encoders are supervised.
Supervision of all encoder types
When two speed sources are used, they are cross-checked against each other.
Supervision of Sin/Cos type encoders
The amplitude of the encoder signals is monitored to keep it within acceptable limits.
Making sure that the encoder signals are in valid differential state (for example, Sin+ to Sin-).
Making sure that the sinus and cosine signals are in phase shift between the different channels.
The tests of the Sin/Cos encoder are equivalent to Sin
2
(x) + Cos
2
(x) = 1.
Supervision of Digital pulse type encoders
Making sure that the encoder signals are in valid differential state (for example, A+ to A-).
Making sure that the signals are in phase shift between the different channels.
Supervision of proximity sensors
Making sure that the proximity sensor signals are in valid differential state (for example, A+, A-).
Diagnostic coverage for the encoder
Sin/Cos 99%
Digital pulse 90%
Proximity sensor 90%
N O T I C E
In addition to the two differential channels used for speed measurement, a reference signal (also called Zero/Z-pulse) can be
used for additional supervision of the correctness of the encoder signals. If the reference signal is parameterized to be used, the
total absence of the reference signal will be detected. The disconnection of one of the differential signals might not be detected.
In such cases, the additional supervision based on the reference signal is not lost.
The tests are done automatically when the motor rotates. To make sure that the correct operation continues, the motor cannot be
kept at standstill for longer than 30 days. In practice, the conditions that are listed below must be valid for the standstill counter to
reset.
When estimated speed is used
Estimated speed is valid (that is, the AC drive is rotating the motor).
Estimated speed and the speed measured by the encoder are greater than the allowed deviation of the speed sources.
When estimated speed is not used
The motor must be rotated for at least two revolutions with a speed above 120/k rpm, where k is "encoder number of pulses" or
"proximity sensor number of pulses", depending on the used speed sensor. If an encoder and a proximity sensor are used, the
calculation must be valid for both.
3.6.7 Usage of Only One Speed Sensor
When a single speed sensor is used, take into account these fault models. To prevent these faults, plan the design and installation of
your system carefully. For more information, see the standard.
AQ319736045637en-000101 / DPD01798 | 39Danfoss A/S © 2021.06
Overview of the System
VACON® NXP Advanced Safety Options
Operating Guide
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