ABB DCS550 - Speed Feedback Monitor; Speed Measurement Supervision

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Fault tracing
3ADW000379R0501 DCS550 Manual e e
− Current near discontinuous level will create values of about 300 % * ConvCurActRel (1.15) if a thyristor is
not fired.
− High inductive loads will create values of about 90% * ConvCurActRel (1.15) if a thyristor is not fired.
Commissioning hint:
It is not possible to pre-calculate clear levels. The current control reacts to unstable current feedback. The
load is continuously driving the current if a thyristor is not fired.
Speed feedback monitor
The speed feedback monitor supervises an attached analog tacho or encoder for proper function by means of
measured speed and measured EMF. Above a certain EMF, the measured speed feedback must be above a
certain threshold. The sign of the speed measurement must be correct as well:
Speed measurement supervision
The drive reacts according to SpeedFbFltSel (30.17) when:
1. the measured EMF is greater than EMF FbMonLev (30.15) and
2. the measured speed feedback SpeedActEnc (1.03), SpeedActTach (1.05) or SpeedActEnc2 (1.42) is lower
than SpeedFbMonLev (30.14).
Example:
− SpeedFbMonLev (30.14) = 15 rpm
− EMF FbMonLev (30.15) = 50 V
The drive trips when the EMF is greater than 50 V while the speed feedback is ≤ 15 rpm.
Speed feedback monitor
SpeedFbFltSel (30.17) selects the reaction to a speed feedback problem:
speed feedback
monitoring (F522) enabled
tacho polarity
monitoring (F553) enabled
Motor
speed
Motor
voltage
Motor speed_volt_a.dsf
EMF FbMonLev (30.15)
Speed FbMonLev (30.14)
speed feedback
monitoring (F522) enabled
tacho polarity
monitoring (F553) enabled