Danfoss VLT AutomationDrive FC 360 Design Manual page 79

Design Guide | VLT® AutomationDrive FC 360
Basic Operating Principles of a Drive
8
Introduction
8.1
This chapter provides an overview of the primary assemblies and circuitry of a Danfoss drive. It describes the internal electrical and signal
processing functions. A description of the internal control structure is also included.
Description of Operation
8.2
A drive is an electronic controller that supplies a regulated amount of AC power to a 3-phase inductive motor. By supplying variable
frequency and voltage to the motor, the drive varies the motor speed or maintains a constant speed as the load on the motor changes.
Also, the drive can stop and start a motor without the mechanical stress associated with a line start.
In its basic form, the drive can be divided into the following 4 main areas:
Rectifier
The rectifier consists of SCRs or diodes that convert 3-phase AC voltage to pulsating DC voltage.
DC link (DC bus)
The DC link consists of inductors and capacitor banks that stabilize the pulsating DC voltage.
Inverter
The inverter uses IGBTs to convert the DC voltage to variable voltage and variable frequency AC.
Control
The control area consists of software that runs the hardware to produce the variable voltage that controls and regulates the AC motor.
1 2
L1
L2
L3
Figure 37: Internal Processing
1
Rectifier (SCR/diodes)
3
Inverter (IGBTs)
Drive Controls
8.3
Overview of Drive Controls
8.3.1
The following processes are used to control and regulate the motor:
Reference handling.
l
Feedback handling.
l
User-defined control structure.
l
Open-loop/closed-loop mode.
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Danfoss A/S © 2024.01
3
U
V
W
4
2
DC link (DC bus)
4
Control
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