The usual measuring points for measuring voltage in power electronics
Measuring voltage to detect whether the IGBT is saturated, bymeasuring the collector-
emitter voltage has already been described in detail in chapter
so in the following
the focuswill beonmeasuring theDC-bus voltage.
There are several reasons why it is important to know the value of the DC-bus voltage.
Firstly, it makes it possible to control theDC-bus chargewhen turning the application on
or recharging the DC-bus in the event of a brief mains voltage drop
Secondly, depending on the DC-bus voltage, it is possible to make independent
adjustments to themodulation factor that controls the output voltage. Thirdly, particularly
in regenerative operation (with no option to regenerate energy into the grid) theDC-bus
voltage must not exceed a certain maximum value, which depends on factors that
include the reverse breakdown voltage of the semiconductors, other electronic features
(e.g. ActiveClamping), theDC-bus capacitors and thedesignof the isolationpaths.
Whenmeasuring theDC-bus voltage, it is important that a high voltagemust be divided
down to a lower measurable voltage, the losses caused by the measurement must be
minimised, and there must be at least a functional or high-impedance isolation of the
measured signal from the subsequent monitoring electronics. Below are two examples.
shows one of several potential realisations based on a high-impedance
separation between theDC-bus potential and themeasuring circuit