Logic Section - Danfoss VLT HVAC Drive FC 100 Service Manual

3 Internal Adjustable Frequency Drive Opera-
tion

3.2.1 Logic Section

The control card contains most of the logic section (see Figure 3-2). The primary logic element of
the control card is a microprocessor, which supervises and controls all functions of adjustable
frequency drive operation. In addition, separate PROMs contain the parameters to provide the
user with programmable options. These parameters are programmed to enable the adjustable
frequency drive to meet specific application requirements. This data is then stored in an EEPROM
3
which provides security during power-down and also allows the flexibility to change the operational
characteristics of the adjustable frequency drive.
A custom integrated circuit generates a pulse width modulation (PWM) waveform which is then
sent to the interface circuitry located on the power card.
Figure 3.2: Logic Section
The PWM waveform is created using an improved control scheme called VVC
opment of the earlier VVC (Voltage Vector Control) system. VVC
and voltage to the motor which matches the requirements of the motor. Also available is the
continuous pulsing SFAVM PWM. Selection can be made in parameter group 14-**. The dynamic
response of the system changes to meet the variable requirements of the load.
Another part of the logic section is the local control panel (LCP). This is a removable keypad/
display mounted on the front of the adjustable frequency drive. The LCP provides the interface
between the adjustable frequency drive's internal digital logic and the operator.
All the adjustable frequency drive's programmable parameter settings can be uploaded into the
EEPROM of the LCP. This function is useful for maintaining a backup adjustable frequency drive
profile and parameter set. It can also be used, through its download function, in programming
other adjustable frequency drives or to restore a program to a repaired unit. The LCP is removable
during operation to prevent undesired program changes. With the addition of a remote mounting
kit, the LCP can be mounted in a remote location of up to ten feet away.
3-2
High Power Service Manual for VLT
MG.90.L1.22 - VLT ® is a registered Danfoss trademark
Adjustable Frequency Drives
plus , a further devel-
plus provides a variable frequency
®
FC Series