KEB COMBIVERT F5 BASIC Applications Manual page 19

Product Description
2. Overview
2.1 Product Description
2.1.1 Features of KEB
COMBIVERT
2.1.2 Function
Principle
© KEB Antriebstechnik, 2002
All Rights reserved
PID-controller
Speed search
Encoder interface
Jogging-function (prog.)
Electr. motor protection
Slip compensation
HSP5 interface
Energy saving function
Power-Off function
Protective equipment
The power circuit of a frequency inverter consists basically of a mains rectifier, the
DC-link and an inverter at the output. The mains rectifier consists of an uncontrolled
single or three-phase bridge connection, the single-phase design is restricted to small
powers. It converts the AC-voltage of the mains into a DC-voltage, which is smoothed
by the DC-link capacitor, thus in the ideal case (inverter unloaded) the DC-link is
charged with a voltage of U
Since during the charging of the DC-link capacitor very high currents flow for a short
time which would lead to the tripping of the input fuses or even to the destruction of
the mains rectifier, the charging current must be limited to a permissible level. This is
achieved by using an inrush current limiting resistor in series to the capacitor. After
the charging of the capacitor is completed the limiting resistor is bridged, for example,
by a relay and is therefore only active at the switch-on of the inverter.
As the smoothing of the DC-link voltage requires a large capacity, the capacitor still
has a high voltage for some time after the disconnection of the inverter from the
mains.
The actual task of the frequency inverter, to produce an output voltage variable in
frequency and amplitude for the control of the three-phase AC motor, is taken over by
the converter at the output. It makes available a 3-phase output voltage according to
the principle of the pulse-width modulation, which generates a sinusoidal current at
the three-phase asynchronous motor
Picture 2.1.2 Block diagram of an inverter power circuit
~
L1
U
N
L2
=
(L3)
Mains rectifier
Name: Basis
KEB COMBIVERT F5
Summary
Autoboost
Prog. Operator menu
DC-braking
8 parameter sets
KEB
COMBIVERT
2 prog. analog output
Hardware current limit
Prog. filter for analog and digital inputs
Adjustable balancing of the ramps
Hour meter
= √2
. U
ZK N.
R
U
ZK
C
DC-link
Date
10.04.02
14 parameter groups
Software In-/Outputs
2 prog. relay outputs
8 prog. digital inputs
2 prog. analog inputs
2 prog. digital output
U
=
V
~
W
Converter Motor
Chapter Section Page
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