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VARIABLE FREQUENCY DRIVE
In addition to using a precision servo motor to control the air flow into a combustion chamber, the
PPC4000 can control one or two variable frequency drives (VFD/VSD) with the result being better
control over air flow and improvements in combus-
tion. Electrical energy savings and additional gains
in efficiency are quickly realized when controlling
the combustion blower motor with a VFD. To
obtain VFD/VSD control, it is necessary to insert a
NXCESVFD plug-in daughter board into the
PPC4000. The NXCESVFD provides two indepen-
dent VFD/VSD channels with each channel con-
taining one precision 4-20 mA output for VFD/
VSD control, one calibrated 4-20 mA input used to
monitor feedback from the VFD/VSD and one
encoder input used to count pulses from a directly
connected shaft encoder. All inputs and outputs are
available through connector P14. Shielded cable
should be used to connect VFD inputs and outputs to the NXCESVFD. Refer to installation manual
NXCESVFD-1001.
Connect shield wires to EARTH post located on PPC4000 chassis.
Alternatively, since the NXCESVFD board supplies a 4-20 mA output, each channel's output can be
designated or mapped to output modulation rate, setpoint, sensor value, servo position and combus-
tion parameters derived from the O2 probe. The intent is to provide this output to a chart recorder or
some other display device of the user's choice. See ANALOG OUT SETUP submenu.
Each VFD channel, if selected to be used as a VFD, is treated in the same manner as a servo motor.
Each VFD is setup and configured through the SERVO SETUP submenu. After menu configuration
the VFD must be commissioned in the profile assigned.
In order to use a VFD output as an indicating device, the VFD channel must not be configured to be
used as a servo. Conversely in order for a VFD channel to be available to be used as a servo, its status
in the ANALOG OUT SETUP submenu must be set to UNUSED. Shown below is the SERVO
SETUP menu after servos have been learned to discover servo 1 and servo 2 and to show that both
channels, VFD1 and VFD2, are available to be used to control VFD's. Any VFD channel used other-
wise in the ANALOG OUT SETUP menu would not be displayed in the servo setup menu.
VFD1
VFD2
Function
4-20 mA Out
[To VFD]
4-20 mA In
[From VFD]
Encoder In
4-20 mA Out
[To VFD]
4-20 mA In
[From VFD]
Encoder In
Signal
P14.6
P14.4
P14.2
P14.5
P14.3
P14.1
Common
P14.12
P14.10
P14.8
P14.11
P14.9
P14.7
NXCESVFD SPECIFICATIONS
VFD OUT:
4-20 mA, Input impedance of external device: Max. 750 ohms
VFD IN:
4-20 mA, Input impedance: 100 ohms
ENCODER IN:
2.4 Kohm pull-up to 24 vdc
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P14 pin 1
P14 pin 7
P14 pin 1
P14 pin 7
