Logic Section; Logic-To-Power Interface - Danfoss VLT FC Series Service Manual

Internal Drive Operation

5.2.1 Logic Section

Microprocessor
The control card contains most of the logic section (see
Illustration 5.2). The primary logic element of the control
card is a microprocessor, which supervises and controls all
functions of operation of the drive. In addition, separate
PROMs contain the parameters to provide programmable
options. These parameters are programmed to enable the
drive to meet specific application requirements. This data is
then stored in an EEPROM which provides security during
power-down and allows for changing the operational
5 5
characteristics of the drive.
PWM waveforms
A custom-integrated circuit generates a pulse width
modulation (PWM) waveform which is then sent to the
interface circuitry on the power card.
RAM
Control
Illustration 5.2 Logic Section
The PWM waveform is created using an improved control
scheme called VVC
VVC (voltage vector control) system. VVC
variable frequency and voltage to the motor which
matches the requirements of the motor.
Local control panel (LCP)
Another part of the logic section is the local control panel
(LCP). The LCP is a removable keypad/display mounted on
the front of the drive. The LCP provides the interface
between the internal digital logic and the operator.
All the programmable parameter settings can be uploaded
into the EEPROM of the LCP. This function is useful for
maintaining a back-up drive profile and parameter set. It
can also be used, through its download function, in
programming other drives or to restore a program to a
repaired unit. The LCP is removable during operation to
44
VLT
Local
Control
Panel
Data
D
VVC
PROM +
EEPROM
Power
feedback
Power
D
+
, a further development of the earlier
+
provides a
Danfoss A/S © 02/2019 All rights reserved.
®
FC Series, D1h–D8h, Da2/Db2/Da4/Db4, E1h–E4h, J8/J9
prevent undesired program changes. With the addition of a
remote mounting kit, the LCP can be mounted in a remote
location of up to 3 m (10 ft) away.
Control terminals
Control terminals, with programmable functions, are
provided for input commands such as run, stop, forward,
reverse, and speed reference. Extra output terminals are
provided to supply signals to run peripheral devices or for
monitoring and reporting status.
The control card logic can communicate via serial link with
outside devices such as personal computers or
programmable logic controllers (PLC).
The control card also provides 2 voltage supplies for use
from the control terminals. The 24 V DC is used for
switching functions such as start, stop, and forward/
reverse. The 24 V DC supply can supply 200 mA of power,
part of which can be used to power external encoders or
other devices. A 10 V DC supply on terminal 50 is rated at
17 mA is also available for use with speed reference
circuitry.
The analog and digital output signals are powered through
Analog
an internal drive supply.
inputs
A
2
Two relays for monitoring the status of the drive are on
the power card. They are programmable through
Digital
inputs parameter group 5-4* Relays. The relays have different
1
ratings. See the corresponding operating guide or design
guide for more information on ratings.
Analog
outputs
A
The control card logic circuitry allows for the addition of
1
option modules for synchronizing the following types of
software:
Digital
channel
•
1
Control
•
Serial communications
Relay
•
Extra relays
•
Cascade pump controller
•
Custom operating

5.2.2 Logic-to-power Interface

The logic-to-power interface isolates the high voltage
components of the power section from the low voltage
signals of the logic section. The interface section consists
of the power card and gate drive card.
Control card
The control card handles much of the fault processing for
output short circuit and ground fault conditions. The
power card provides conditioning of these signals. The
control card also handles scaling of current and voltage
feedback.
Power card
The power card contains a switch mode power supply
(SMPS), which provides the unit with 24 V DC, (+) 18 V DC,
(–) 18 V DC, and 5 V DC operating voltage. The SMPS
MG94A502