Modbus Instruction manual 6305/08
05/08
Modbus Instruction manual 63
9.2 Reference Value
9.2.1 Reference Frequency
The following signal sources are available for determining the reference frequency:
− External reference value as reference line value from bus
− Internal reference value from the reference frequency channel
The reference line value with the parameter name Reference Frequency RAM 484 is
sent to the frequency inverter via the bus.
The internal reference value reaches the frequency inverter via the reference fre-
quency channel. The reference frequency channel is configured via parameter
Refer-
ence Frequency Source
475.
The actual value can be read back vie different parameters. The selection depends on
the control method used and the application. The following parameters are possible,
for example:
− Stator Frequency 210 (data type long, Hz)
− Encoder 1 Frequency 217
(Speed Sensor 1 Frequency)
(data type long, Hz)
− Encoder 1 Speed 218
(Speed Sensor 1 Speed)
(data type int, rpm).
fmin
fmax
Ramp
Reference Ramp
Frequency
283
+
+
0
0
Reference line value
from Bus
Internal reference
value of
reference frequency
channel
ramp function
Operation Mode
Ramp Setpoint
434
Reference Frequency
RAM
484
The internal reference value from the reference frequency channel and the reference
line value (line setpoint) can be fed to the ramp individually or as an added variable.
The result is available at the output of the ramp function as
Refer-
ence Ramp Frequency
283.
The operation mode of the ramp function is set via the data set related parameter
Ramp Setpoint 434.
For information on the reference frequency channel, refer to the frequency inverter
operating instructions.
Ramp Setpoint 434 Function
1 – Internal Setpoint
The internal reference frequency is determined
from the reference frequency channel.
2 – Line Setpoint
The reference value is supplied externally via the
bus
3 – Internal + Line Setpoint
Addition (considering the sign) of internal refer-
ence frequency and reference line value
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