Danfoss VLT 3032 Service Manual page 8

POWER SECTION
RECTIFIER
R
S
T
The power section is made up of the SCR/Diode modules (input
rectifiers), the soft charge circuit, the DC capacitor bank, the gate drive
and snubber cards and the IGBT power devices. Also located in the
power section are the DC Bus coil, the motor coils and, although not
typically considered part of the power section, the output phase current
sensors.
During the troubleshooting process, extreme care is required when
probing into the power section components. The DC Bus, when fully
charged, can be as high as 350VDC. Although this voltage begins to
decrease upon the removal of input power, it takes up to approximately
fifteen minutes to fully discharge the DC capacitor bank. Located on
the interface board is the Bus Charged Indicator. The red LED is visible
through the shield covering the lower portion of the interface board;
and as long as it is lit it indicates the DC Bus voltage is greater than
50VDC. A fault in the power section will usually result in at least one of
the incoming line fuses being blown. If one or more line fuses have
blown, it is not recommended to replace them and reapply power without
further investigation. In a case such as this, it would be suggested to
conduct the tests listed under Static Test Procedures in Section Three.
These tests will result in a thorough check of all the components
operating in the power section. In addition, following the identification
and replacement of power section components, it is recommended to
disconnect the motor wires prior to reapplying power. This precaution
opens the path for short circuit currents through the motor in the case
that all faulty components have not been replaced.
DC BUS
SIMPLFIED PWM POWER SECTION
8
INVERTER
M
3Ø