Operating manual 810353-BALDE-150220
Version 20.02.2015
Page 15 of 36
7. Structure and function description
7.1.
General Information
The high-voltage generator is built in a compact design. The controls, end stage, HV
transformer and the HV cascade are combined in one device. The unit is supplied with
3-phase 400 V 50/60 Hz. The controls are separately supplied with 24 V. The power
output stage has its own µController, which guarantees a precise and very fast control.
The control module takes over all control functions with a separate microcontroller and
establishes communication to the outside using CANopen.
The temperature of the end stage and the aluminum housing is monitored. If there is an
impermissible temperature increase there is first a warning and if it continues to in-
crease there is a shutdown.
7.2.
Safety concept
Communication of both µcontrollers is permanently monitored. As soon as the commu-
nication is defective or interrupted, there is a shutdown and an error is reported.
The internal measurement resistance of the cascade, the current measurement and the
internal protection circuit undergo a plausibility test each time the high voltage is
switched on. This test runs at the start of the start up ramp and is completed after ap-
prox. 200 ms. If the test fails there is an immediate shut down and an error is reported.
The actual applied high voltage is continuously measured and monitored. The control
can be preset with the system capacity via CANopen. The factory setting is at 3 nF.
According to the formula:
E= C1/2 X U
2
E = Residual energy in joules [J]
C = System capacity in farad [F]
U = Voltage in volts [V]
the µController calculates the dangerous voltage level.
Basics for this are 0.24 mJ. At 3 nF and 0.24 mJ the voltage threshold lies at 400 V. As
soon as the applied high voltage lies above this value "unsafe" is reported, regardless
of whether the high voltage is switched on or not. If the high voltage lies below 400 V
(with setting 3nF) “safe" is reported. The message is output via CANopen and is addi-
tionally available as potential-free relay output. The relay is a safety relay and is con-
tinuously monitored. For additional safety the relay is delayed by 10 seconds after
switching off the high voltage regardless of U actual (see also 4.3).
High voltage-ON is additionally reported via CANopen if the high voltage is switched on
and the output voltage has reached at least 90 % of U target.
The 400 V input voltage is measured on the power module and monitored. With more
that 10% over-voltage there is a shut down and an error is reported. If the 400 V is not
applied an error is also output.
