Speed Feedback And Speed Reference Handling; Speed Scaling To Software; Speed_Measurment Function Block - ABB DCS 500B Description

• Speed feedback and
speed reference hand-
ling
Speed scaling to
software
SPEED_MEASURME
NT function block
DCS 500 Software Description
The speed feedback signals can be taken from three different
sources:
•
by means of analog tacho generator
•
by means of a pulse encoder
•
from the EMF signal, calculated by the converter by means of
the converter´s output voltage
The speed reference for speed control can be given in several
ways:
•
by means of analog input
•
from a constant reference source
•
reference up/down counter
•
application program
•
CDP312 panel or CMT/DCS500 Tool
The speed values (ref./act.) are scaled so that 20000 units in soft-
ware equals to the drive's maximum speed which is set in pa-
rameter SPEED SCALING (2103) in 0.1 rpm accuracy. For exam-
ple, maximum speed is 1000 rpm. SPEED SCALING would be set
to 10000. When speed reference is 10000, the motor runs at 500
rpm. The maximum value of the speed reference is -30000 or
+30000 depending on which direction of rotation is used.
The speed of the motor can be measured in three different ways:
by an incremental encoder, by an analogue tacho generator or by a
calculated/measured EMF-voltage. Speed measurement with the
pulse encoder has four different modes. The difference between
these modes is in the accuracy of the measurement, which de-
pends on the type of pulse encoder.
The analogue tacho generator is connected to the analogue input
channel AITAC. The input voltage range is -10V...+10V and accu-
racy of A/D-conversion is 13 bits. If higher than 10V tacho genera-
tor is used, the scaling of incoming voltage can be done on I/O-
board SDCS-IOB-1 and in case of I/O-board SDCS-IOB-3 with ex-
ternal circuits (PS5311). The software of the DCS 500B includes
scaling parameters for adjusting the analogue speed feedback.
Functional Software description
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