Example: Scaling of the speed in the process data channel
This example shows the coding you must apply to transfer the speed setpoint through the process
data channel so that the drive will operate at 400 1/min in CLOCKWISE direction of rotation or at 750
1/min in COUNTER CLOCKWISE direction of rotation.
Direction of
rotation
Speed
Scaling
Transferred process data
CW
400 1/min
400
= 2000
dec
= 07D0
hex
0.2
2000
dec
or 07D0
hex
resp.
CCW
750 1/min
750
(-1) ·
= -3750
dec
= F15A
hex
0.2
-3750
dec
or F15A
hex
resp.
Scaling of the Relative Speed
The process data relative speed setpoint [%] and relative actual value of speed [%] are specified in
[% f
max
] as percentage of the valid maximum frequency of the inverter and are represented signed in
a process data word (16-bit-integer). The following table displays the scaling for the process data of
the type “relative speed”.
Data type:
Integer16
Resolution:
1digit = 0.0061 % (4000
hex
= 100 %)
Reference:
Maximum frequency of the inverter (f
max
)
Range:
-3276.8 % ....0..... +3276.7 %
8000
hex
.....0.....7FFF
hex
Valid for:
Relative speed setpoint [%]
Relative actual value of speed [%]
Providing the motor is wired correctly, positive speed values indicate CLOCKWISE (CW) direction of
rotation and in cases of hoist applications CLOCKWISE direction of rotation = UP. Negative speed
values consequently indicate COUNTERCLOCKWISE (DOWN) direction of rotation and are
represented as a two’s complement.
Example: Scaling of the relative speed in the process data channel
This example shows, which code the relative speed setpoint [%] must be transferred over the process
data channel with, in order to be able to operate the drive clockwise with 25% of the maximum
frequency respectively counter clockwise with 75% of the maximum frequency.
Direction of
rotation
Rel. Speed
Scaling
Transferred process data
CW
25 % f
max
16384
25 ·
= 4096
dec
= 1000
hex
100
4096
dec
or 1000
hex
resp.
CCW
75 % f
max
16384
(-75) ·
= -12288
dec
= D000
hex
100
-12288
dec
or D000
hex
resp.
With the maximum frequency set to f
max
= 50 Hz the drive in this example will rotate clockwise with
12.5 Hz respectively counterclockwise with 37.5 Hz.
Inverter Control
with Process Data
3
22
MOVITRAC
®
31.. Fieldbus Unit Profile
Phone: 800.894.0412 - Fax: 888.723.4773 - Web: www.clrwtr.com - Email: [email protected]
