Description Of Operation - Danfoss VLT Refrigeration Drive FC 103 Design Manual

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2.2 Description of Operation

The frequency converter supplies a regulated amount of
mains AC power to the motor to control its speed. The
frequency converter supplies variable frequency and
voltage to the motor.
The frequency converter is divided into 4 main modules:
•
Rectifier
•
Intermediate DC bus circuit
•
Inverter
•
Control and regulation
Illustration 2.6 is a block diagram of the internal
components of the frequency converter.
Area Title
•
3-phase AC mains supply to the
1 Mains input
frequency converter.
•
The rectifier bridge converts the
AC input to DC current to supply
2 Rectifier
inverter power.
•
Intermediate DC bus circuit
3 DC bus
handles the DC current.
•
Filter the intermediate DC circuit
voltage.
•
Prove mains transient protection.
•
Reduce RMS current.
4 DC reactors
•
Raise the power factor reflected
back to the line.
•
Reduce harmonics on the AC
input.
•
Stores the DC power.
•
5 Capacitor bank Provides ride-through protection
for short power losses.
•
Converts the DC into a controlled
PWM AC waveform for a
6 Inverter
controlled variable output to the
motor.
•
Regulated 3-phase output power
7 Output to motor
to the motor.
MG16G202
Design Guide
Functions
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Area Title
•
Input power, internal processing,
output, and motor current are
monitored to provide efficient
operation and control.
•
User interface and external
8 Control circuitry
commands are monitored and
performed.
•
Status output and control can be
provided.
Illustration 2.6 Frequency Converter Block Diagram
Functions
2
17
2