Download English

General Information
1.5
Power Section
The input rectifier converts the three-phase line voltage to a pulsating DC voltage. The subsequent DC link capacitor serves as an energy buffer that smoothes the pulsating DC voltage. When the line is connected, the charging unit ensures smooth charging of the capacitor. Figure 1.1 shows a triac for bridging the load resistor. Dependent on output, the charging circuit may vary. For instance, relays or also half-controlled bridge-connected rectifiers
are also used. The charging connection in inverters of 75 kW or greater is located on the
minus side of the intermediate circuit. This is especially the case with the parallel connection of the intermediate circuit DC connections of several inverters. The variables used are
described in more detail in the following table:
Charging connection (CC)
CC in + or –
intermediate circuit
II red
Charging relay – braking chopper resistor is used as the
charging resistor
+
III red
Charging relay – a special charging resistor is used
+
IV...VI
Semi-controlled rectifier bridge. Thyristors between intermediate circuit + and the single network phases (threephase)
VII
Charging relay – a special charging resistor is used
–
VIII...IX Charging relay – a special charging resistor is used
–
Size
between ~ and +
NOTES:
For all inverter sizes, the intermediate connections are located directly at the intermediate
circuit capacitors, i.e. the internal charging connection is not used with a DC feed.
The complete inverter bridge, consisting of IGBTs (insulated gate bipolar transistors) is integrated in an intelligent power module (IPM). This converts the DC voltage of the DC link
back to a three-phase voltage. By control of the IGBTs with suitable pulse patterns (PWM
signals), it is possible to control both the output frequency and the output voltage continuously.
For regenerative operation of the drive, the chopper transistor switches a ballast resistor
into the DC link in order to convert the accumulating brake energy to heat.
The line voltage input filter and the DC link choke serve the purpose of radio frequency interference suppression.
The switched mode power supply unit connected to the DC link generates all necessary
supply voltages. The power supply unit operates provided the DC link voltage does not drop
below 310 V.
The DC link circuits can be electrically connected when operating several inverters in one
system. In this way, regeneratively operating inverters may supply the energy for motivepower inverters, thus extracting less energy from the line and simultaneously relieving the
braking resistor. However, BERGES should be consulted in this case.
When it lights up, a voltage pilot lamp (BUS CHG, incandescent bulb; present only on units
up to 55 kW) signals that the DC link voltage is higher than 80 VDC. The voltage pilot lamp
is visible through a hole above the power terminals.
04.08.05
Operating Instructions
07_GB_T1
UD 7000 — 1.5–355.0
1-7