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Internal Frequency Converte...
Illustration 3.3 Logic Section
The PWM waveform is created using an improved control
scheme called VVC
plus
, a further development of the earlier
VVC (Voltage Vector Control) system. VVC
variable frequency 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 frequency converter. The LCP provides the
interface between the frequency converter's internal digital
logic and the operator.
All the frequency converter's programmable parameter
settings can be uploaded into the EEPROM of the LCP. This
function is useful for maintaining a backup frequency
converter profile and parameter set. It can also be used,
through its download function, in programming other
frequency converters 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.
Control terminals, with programmable functions, are
provided for input commands such as run, stop, forward,
reverse and speed reference. Additional output terminals
are provided to supply signals to run peripheral devices or
for monitoring and reporting status.
High Power Service Manual for Modular F Frame Drives
The control card logic is capable of communicating via
serial link with outside devices such as personal computers
or programmable logic controllers (PLC).
The control card also provides two voltage supplies for use
from the control terminals. The 24 VDC is used for
switching functions such as start, stop and forward/reverse.
The 24 VDC supply is also capable of supplying 200 mA of
power, part of which may be used to power external
encoders or other devices. A 10 VDC 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
an internal frequency converter supply.
Two relays for monitoring the status of the frequency
converter are located on the power card. These are
programmable through parameter group 5-4*. The relays
are Form C, meaning it has one normally open contact and
one normally closed contact on a single throw. The
contacts of the relay are rated for a maximum load of 240
VAC at 2 Amps resistance.
plus
provides a
The logic circuitry on the control card allow for the
addition of option modules for synchronising control, serial
communications, additional relays, the cascade pump
controller, or custom operating software.
3.2.2 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.
Much of the fault processing for output short circuit and
earth fault conditions is handled by the control card. The
power card provides conditioning of these signals. Scaling
of current feedback and voltage feedback is accomplished
by the control card.
The power card contains a switch mode power supply
(SMPS) which provides the unit with 24 VDC, +18 VDC, –18
VDC and 5 VDC operating voltage. The logic and interface
circuitry is powered by the SMPS. The SMPS is supplied by
the DC bus voltage. The frequency converters can be
purchased with an optional secondary SMPS which is
powered from a customer supplied 24 VDC source. This
secondary SMPS provides power to the logic circuitry with
main input disconnected. It can keep units with communi-
cation options live on a network when the frequency
converter is not powered from the mains.
®
MG90K202 - VLT
is a registered Danfoss trademark
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3
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