4.4.14.1 Precharging of the DC link
If the DC link voltage falls below the UP threshold, the circuit for the current-limited
precharging of the DC link is activated.
Below the UP threshold, the switching power supplies connected to the high volt-
age also become inactive. This triggers error 123: ERROR PUready. Since the UP
level is fallen below when the voltage is switched off before the switching power
supplies become inactive, error "ERROR PUready" is normally never visible to the
outside.
"5: phase failure“ is displayed in parameter ru04 supply unit state.
Precharging occurs via precharging resistors, which are bridged after completion of
precharging either via a relay (case size 2) or input thyristors.
The difference between the DC link voltage and the mains input voltage is moni-
tored from housing size 4.
The power unit ready signal is only set when the high-voltage supplied power units
are in operation and the voltage difference monitoring also sends the "ready" sig-
nal.
When the power unit ready signal is applied and the UP reset threshold is ex-
ceeded, the precharge time implemented in the software also elapses. After this
time, the precharging circuit is deactivated again and the state of parameter ru04
supply unit state changes to "4: run“.
The time until the UP reset threshold is reached or the power unit ready signal is
set is only defined by the hardware (temperature-dependent precharging resistors).
If the error was triggered by a short power failure, the restart time can be optimized
by reducing the software waiting time. For this, bit 2 "reduced charging" must be
activated in pn84[2] fault supression mode.
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