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Overview
Overview
AFDG/AFDU Information
The AFDG/AFDU air-cooled Adaptive Frequency Drive is a
pulse width modulated (PWM) design. It is designed for
460/480/575 volt application. This drive converts AC power
to DC power and back to AC power. The incoming 460/480/
575 volts are converted to a constant 650 Vdc by a rectifier
bridge (SCRs and diodes), and into a section of capacitors
that are used to store the DC voltage. The DC output feeds
the inverter IGBTs that switch at predetermined time to
change the DC input voltage to a symmetrical AC output
voltage of desired magnitude and frequency. The output
frequency range is 38 to 60 hertz.
The DC voltage is fixed at 700 Vdc. A variable output is
accomplished by PWM control within the inverter by the
IGBTs which are basically transistors that turn on and off
in response to the gate driver.
A combination of two distinct operating modes make up
the AFDG/AFDU control within the chiller's UC800 control.
First by controlling the inlet vanes, and second by
modulating impeller speed from 38 to 60 hertz. The IGBTs
control the speed in response to the UC800 compressor
control signal. Circuit breakers, surge capacitors and
ground faults are standard on all AFDG/AFDU units.
Some of the basic principles of the drive are:
•
Minimum efficiency of 97 percent at rated load and
60 Hz.
•
Unit displacement power factor of 0.96 at all loads.
•
Low starting current.
•
The current never exceeds the rated load amps.
•
The AFDG/AFDU varies the motor speed in response to
the speed command from the UC800 control.
The CenTraVac™ Control Panel has full control of the unit
operation, including the start/stop functions. If you
encounter a fault condition or an alarm on the drive, the
Tracer® AdaptiView™ display will indicate "alarm" and an
"alarm message."
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AFDG-SVU01L-EN
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